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  • 51.
    Banerjee, Amitava
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Araujo, Rafael B.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Royal Inst Technol KTH, Dept Mat & Engn, Appl Mat Phys, S-10044 Stockholm, Sweden.
    Unveiling the thermodynamic and kinetic properties of NaxFe(SO4)2 (x = 0–2): toward a high-capacity and low-cost cathode material2016In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 4, p. 17960-17969Article in journal (Refereed)
    Abstract [en]

    The mineral eldfellite, NaFe(SO4)2, was recently proposed as an inexpensive candidate for the next generation of cathode application in Na-based batteries. Employing the density functional theory framework, we have investigated the phase stability, electrochemical properties and ionic diffusion of this eldfellite cathode material. We showed that the crystal structure undergoes a volume shrinkage of ≈8% upon full removal of Na ions with no imaginary frequencies at the Γ point of phonon dispersion. This evokes the stability of the host structure. According to this result, we proposed structural changes to get higher specific energy by inserting two Na ions per redox-active metal. Our calculations indicate NaV(SO4)2 as the best candidate with the capability of reversibly inserting two Na ions per redox center and producing an excellent specific energy. The main bottleneck for the application of eldfellite as a cathode is the high activation energies for the Na+ ion hop, which can reach values even higher than 1 eV for the charged state. This effect produces a low ionic insertion rate.

  • 52.
    Banerjee, Amitava
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Araujo, Rafael Barros
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Sjödin, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Royal Inst Technol KTH, Appl Mat Phys, Dept Mat, S-10044 Stockholm, Sweden;Royal Inst Technol KTH, Appl Mat Phys, Dept Engn, S-10044 Stockholm, Sweden.
    Identifying the tuning key of disproportionation redox reaction in terephthalate: A Li-based anode for sustainable organic batteries2018In: Nano Energy, ISSN 2211-2855, E-ISSN 2211-3282, Vol. 47, p. 301-308Article in journal (Refereed)
    Abstract [en]

    The ever-increasing consumption of energy storage devices has pushed the scientific community to realize strategies toward organic electrodes with superior properties. This is owed to advantages such as economic viability and eco-friendliness. In this context, the family of conjugated dicarboxylates has emerged as an interesting candidate for the application as negative electrodes in advanced Li-ion batteries due to the revealed thermal stability, rate capability, high capacity and high cyclability. This work aims to rationalize the effects of small molecular modifications on the electrochemical properties of the terephthalate anode by means of first principles calculations. The crystal structure prediction of the investigated host compounds dilithium terephthalate (Li2TP) and diethyl terephthalate (Et2Li0TP) together with their crystal modification upon battery cycling enable us to calculate the potential profile of these materials. Distinct underlying mechanisms of the redox reactions were obtained where Li2TP comes with a disproportionation reaction while Et2Li0TP displays sequential redox reactions. This effect proved to be strongly correlated to the Li coordination number evolution upon the Li insertion into the host structures. Finally, the calculations of sublimation enthalpy inferred that polymerization techniques could easily be employed in Et2Li0TP as compared to Li2TP. Similar results are observed with methyl, propyl, and vinyl capped groups. That could be a strategy to enhance the properties of this compound placing it into the gallery of the new anode materials for state of art Li-batteries.

  • 53.
    Banerjee, Amitava
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Chakraborty, Sudip
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Royal Inst Technol KTH, Dept Mat & Engn, Appl Mat Phys, S-10044 Stockholm, Sweden..
    Bromination-induced stability enhancement with a multivalley optical response signature in guanidinium [C(NH2)(3)](+)-based hybrid perovskite solar cells2017In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 5, no 35, p. 18561-18568Article in journal (Refereed)
    Abstract [en]

    Guanidinium lead iodide (GAPbI(3)) has been synthesized experimentally, but stability remains an issue, which can be modulated by the insertion of bromine (Br) into the system. We have performed a systematic theoretical investigation to see how bromination can tune the stability of GAPbI(3). The optical properties were also determined, and we have found formation enthalpy-based stability in the perovskite systems, which are active in the visible and IR region even after bromine insertion and additionally more active in the IR range with the transition from GAPbI(3) to GAPbBr(3). The spin orbit coupling effect is considered throughout the band structure calculations. The ensemble of the primary and secondary gaps in the half and fully brominated hybrid perovskites leads to the phenomenon of a multipeak response in the optical spectra, which can be subsequently attributed as multivalley optical response behaviour. This multivalley optical behaviour enables the brominated guanidinium-based hybrid perovskites to exhibit broad light harvesting abilities, and this can be perceived as an idea for natural multi-junction solar cells.

  • 54. Baran, Jakub D.
    et al.
    Kolodziejczyk, Wojciech
    Larsson, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Larsson, Andreas J.
    On the stability of single-walled carbon nanotubes and their binding strengths2012In: Theoretical Chemistry accounts, ISSN 1432-881X, E-ISSN 1432-2234, Vol. 131, no 9, p. 1270-Article in journal (Refereed)
    Abstract [en]

    We have studied the relative stability of hydrogen-terminated single-walled carbon nanotubes (SWNTs) segments, and open-ended SWNT fragments of varying diameter and chirality that are present at the interface of the catalytic metal particles during growth. We have found that hydrogen-terminated SWNTs differ by <1 eV in stability among different chiralities, which presents a challenge for selective and property-controlled growth. In addition, both zigzag and armchair tubes can be the most stable chirality of hydrogen-terminated SWNTs, which is a fundamental obstacle for property-controlled growth utilizing thermodynamic stability. In contrast, the most armchair-like open-ended SWNTs segments are always the most stable ones, followed in sequence by chiral index up to the least stable zigzag segments. We explain the ordering by triple bond stabilization of the carbon dangling bonds at the open ends, which is a fragment stabilization effect that is only manifested when all bonds between two layers are broken. We show convincingly that the bond strength difference between zigzag and armchair tubes is not present when individual bonds are broken or formed.

  • 55. Belonoshko, A. B.
    et al.
    Davis, S.
    Rosengren, A.
    Ahuja, Rajeev
    Johansson, Börje
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Simak, S. I.
    Burakovsky, L.
    Preston, D. L.
    Xenon melting: Density functional theory versus diamond anvil cell experiments2006In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 74, no 5, p. 054114-Article in journal (Refereed)
    Abstract [en]

    We performed two-phase ab initio density functional theory based molecular dynamics simulations of Xe melting and demonstrated that, contrary to claims in the recent literature, the pressure dependence of the Xe melting curve is consistent with the corresponding-states theory as well as with the melting curve obtained earlier from classical molecular dynamics with a Xe pair potential. While at low pressure the calculated melting curve is in perfect agreement with reliable experiments, our calculated melting temperatures at higher pressures are inconsistent with those from the most recent diamond anvil cell experiment. We discuss a possible explanation for this inconsistency.

  • 56. Belonoshko, A. B.
    et al.
    Li, Sa
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Johansson, Börje
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    High-pressure crystal structure studies of Fe, Ru and Os2004In: Journal of Physics and Chemistry of Solids, ISSN 0022-3697, E-ISSN 1879-2553, Vol. 65, no 8-9, p. 1565-1571Article in journal (Refereed)
    Abstract [en]

    In order to reveal structural trends with increasing pressure in d transition metals, we performed full potential linear muffin-tin orbital calculations for Fe, Ru, and Os in the hexagonal close packed structure. The calculations cover a wide volume range and demonstrate that all these hexagonal close-packed metals have non-ideal c/a at low pressures which, however, increases with pressure and asymptotically approaches the ideal value at very high compressions. These results are in accordance with most recent experiment for Ru and Os. The experimental data for iron is not conclusive, but it is believed that the c/a ratio decreases weakly with increasing pressure at moderate compression. Since, the experimental and calculated equations of state for iron are in increasingly good agreement with increasing pressure, it is possible that either the negative c/a trend is valid only for a restricted pressure range, or related to the experimental difficulties (e.g. non-hydrostaticity).

  • 57.
    Belonoshko, Anatoly B.
    et al.
    Condensed Matter Theory, Department of Theoretical Physics, AlbaNova University Center, KTH Royal Institute of Technology, SE- 106 91 Stockholm, Sweden.
    Ramzan, Muhammad
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Mao, Ho-kwang
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Applied Materials Physics, Department of Materials and Engineering, Royal Institute of Technology (KTH), SE-100 44 Stockholm, Sweden.
    Atomic Diffusion in Solid Molecular Hydrogen2013In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 3, p. 2340-Article in journal (Refereed)
    Abstract [en]

    We performed ab initio molecular dynamics simulations of the C2c and Cmca-12 phases of hydrogen at pressures from 210 to 350 GPa. These phases were predicted to be stable at 0 K and pressures above 200 GPa. However, systematic studies of temperature impact on properties of these phases have not been performed so far. Filling this gap, we observed that on temperature increase diffusion sets in the Cmca-12 phase, being absent in C2c. We explored the mechanism of diffusion and computed melting curve of hydrogen at extreme pressures. The results suggest that the recent experiments claiming conductive hydrogen at the pressure around 260 GPa and ambient temperature might be explained by the diffusion. The diffusion might also be the reason for the difference in Raman spectra obtained in recent experiments.

  • 58. Belonoshko, Anatoly
    et al.
    Skorodumova, Natalia
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics IV.
    Rosengren, Anders
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics IV.
    Johansson, Börje
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics IV.
    Burakovsky, Leonid
    Preston, D. L.
    High-pressure melting of MgSiO32005In: Phys. Rev. Lett.,, Vol. 94, p. 195701-Article in journal (Refereed)
  • 59. Benhouria, Y.
    et al.
    Essaoudi, I.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Ainane, A.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Saber, M.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Dujardin, F.
    Monte Carlo Study of Long-Range Interactions of a Ferroelectric Bilayer with Antiferroelectric Interfacial Coupling2013In: Journal of Superconductivity and Novel Magnetism, ISSN 1557-1939, E-ISSN 1557-1947, Vol. 26, no 10, p. 3075-3083Article in journal (Refereed)
    Abstract [en]

    By the use of Monte Carlo simulation, we have studied the critical behavior of a ferroelectric bilayer with antiferroelectric interfacial coupling using the transverse spin- Ising model. We discuss the effects of long-range interactions for the internal energy, specific heat, free energy, dielectric susceptibility, and polarization. The dependence of the Curie temperature on the thickness of the bilayer, long-range interactions, and the transverse field was also investigated. It is assumed that the long-range interaction decays with the distance between the pseudo-spins as a power law.

  • 60.
    Benhouria, Y.
    et al.
    Univ Moulay Ismail, Fac Sci, Dept Phys, Unite Associee CNRST URAC 08,LP2MS, Meknes, Morocco..
    Essaoudi, I.
    Univ Moulay Ismail, Fac Sci, Dept Phys, Unite Associee CNRST URAC 08,LP2MS, Meknes, Morocco..
    Ainane, Abdelmajid
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Univ Moulay Ismail, Fac Sci, Dept Phys, Unite Associee CNRST URAC 08,LP2MS, Meknes, Morocco.;Max Planck Inst Phys Complexer Syst, D-01187 Dresden, Germany..
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Hysteresis Behavior and Pyroelectric Properties of Multi-Surface Ferroelectric Thin Films2015In: Zhongguó wùli xuékan, ISSN 0577-9073, Vol. 53, no 4, article id 080802Article in journal (Refereed)
    Abstract [en]

    Using the transverse Ising model, we investigate the dielectric properties and the hysteresis behavior of multi-surface ferroelectric (MSF) thin films in the framework of the effective field theory based on the probability distribution technique that accounts for the self-spin correlation functions. The effects of the exchange interactions and the transverse field on the longitudinal and the transverse polarizations, the dielectric susceptibility, the pyroelectric coefficient, and the hysteresis loops are studied. A number of interesting phenomena have been found.

  • 61. Benhouria, Y.
    et al.
    Essaoudi, I.
    Ainane, Abdelmajid
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Dujardin, F.
    Dielectric Properties and Hysteresis Loops of a Ferroelectric Nanoparticle System Described by the Transverse Ising Model2014In: Journal of Superconductivity and Novel Magnetism, ISSN 1557-1939, E-ISSN 1557-1947, Vol. 27, no 9, p. 2153-2162Article in journal (Refereed)
    Abstract [en]

    In this work, we use the effective field theory based on the probability distribution method to investigate the longitudinal and transverse polarizations, susceptibility, pyroelectric coefficient, and the hysteresis behavior of a ferroelectric cubic nanowire. The effects of the core-shell exchange interaction and the core-shell transverse fields on the longitudinal and transverse polarizations, the susceptibility, the pyroelectric coefficient, and the hysteresis loops of the system are examined. Some characteristic phenomena are found in the thermal variations, depending on the physical parameters in the shell and in the core.

  • 62.
    Benhouria, Y.
    et al.
    Univ Moulay Ismail, LP2MS, CNRST URAC 08, Phys Dept,Fac Sci, Meknes, Morocco..
    Essaoudi, I.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Univ Moulay Ismail, LP2MS, CNRST URAC 08, Phys Dept,Fac Sci, Meknes, Morocco..
    Ainane, Abdelmajid
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Univ Moulay Ismail, LP2MS, CNRST URAC 08, Phys Dept,Fac Sci, Meknes, Morocco.;Univ Lorraine, LCP A2MC, Inst Chim Phys & Mat, Metz, France..
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Dujardin, F.
    Univ Lorraine, LCP A2MC, Inst Chim Phys & Mat, Metz, France..
    Monte Carlo simulation of dielectric properties of a mixed spin-3/2 and spin-5/2 Ising ferrielectric nanowires2017In: Ferroelectrics (Print), ISSN 0015-0193, E-ISSN 1563-5112, Vol. 507, no 1, p. 58-68Article in journal (Refereed)
    Abstract [en]

    Dielectric properties of Ising ferrielectric nanowires with spin-3/2 core and spin-5/2 shell structure are systematically studied by the use of the Monte Carlo simulation in the presence of the external longitudinal electric field. Special focus is given to the effects of the core and shell interactions, the interface coupling and the temperature on the core and shell polarizations, the specific heat, the compensations points, the susceptibility and hysteresis behaviors. Some characteristic behaviors are found, such as the existence of triple hysteresis loops for appropriate values of the system parameters affected by the antiferroelectric interface coupling constant and the temperature. The results are compared with those of recently published works and a qualitatively good agreement is found.

  • 63. Benhouria, Y.
    et al.
    Essaoudi, I.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Ainane, Abdelmajid
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Dujardin, F.
    Thermodynamic properties and hysteresis behaviors of a mixed spin-3/2 and spin-1/2 Ising double walled ferrielectric nanotubes: A Monte Carlo study2014In: Superlattices and Microstructures, ISSN 0749-6036, E-ISSN 1096-3677, Vol. 75, p. 761-774Article in journal (Refereed)
    Abstract [en]

    The hysteresis loops and the thermodynamic properties of a ferroelectric or ferrielectric double walled nanotubes (A and B) are studied within the Ising model with mixed spins (S-A = 3/2 and S-B = 1/2) in the presence of the crystal and the external longitudinal electric fields. We use the Monte Carlo method to investigate the effects of the external electric field, the crystal field and the exchange interactions on the total polarization, susceptibility, specific heat and the internal energy of a double walled nanotubes (DWNTs).

  • 64.
    Benhouria, Y.
    et al.
    Univ Moulay Ismail, Unite Associee CNRST URAC 08, LP2MS, Phys Dept,Fac Sci, BP 11201, Meknes, Morocco..
    Oubelkacem, A.
    Univ Moulay Ismail, Unite Associee CNRST URAC 08, LP2MS, Phys Dept,Fac Sci, BP 11201, Meknes, Morocco..
    Essaoudi, I.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics. Univ Moulay Ismail, Unite Associee CNRST URAC 08, LP2MS, Phys Dept,Fac Sci, BP 11201, Meknes, Morocco..
    Ainane, A.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics. Univ Moulay Ismail, Unite Associee CNRST URAC 08, LP2MS, Phys Dept,Fac Sci, BP 11201, Meknes, Morocco.;Max Planck Inst Phys Complexer Syst, Nothnitzer Str 38, D-01187 Dresden, Germany..
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Dynamic Magnetic Properties of a Mixed Spin Ising Double-Walled Ferromagnetic Nanotubes: A Dynamic Monte Carlo Study2017In: Journal of Superconductivity and Novel Magnetism, ISSN 1557-1939, E-ISSN 1557-1947, Vol. 30, no 3, p. 839-844Article in journal (Refereed)
    Abstract [en]

    Using the dynamic Monte Carlo simulation, the dynamic critical temperature of a ferromagnetic or ferrimagnetic double-walled nanotubes (DWNTs) is studied within the kinetic Ising model under the presence of a time-dependent oscillating external magnetic and crystal fields with mixed spins S (A) = 1 and S (B) = 3/2. The effects of the time-dependent oscillating external magnetic field, the period of the oscillating magnetic field, and the crystal field on the thermal behavior of the dynamic sub-lattice order parameters and the total dynamic order parameter, total dynamical magnetic susceptibility, dynamical specific heat, and dynamic hysteresis of a DWNTs are studied. Our theoretical predictions may be a reference for future experiment studies of the nanostructures.

  • 65. Benson, Daryn
    et al.
    Li, Yanling
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Luo, Wei
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Svensson, Gunnar
    Haussermann, Ulrich
    Lithium and Calcium Carbides with Polymeric Carbon Structures2013In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 52, no 11, p. 6402-6406Article in journal (Refereed)
    Abstract [en]

    We studied the binary carbide systems Li2C2 and CaC2 at high pressure using an evolutionary and ab initio random structure search methodology for crystal structure prediction. At ambient pressure Li2C2 and CaC2 represent salt-like acetylides consisting of C-2(2-) dumbbell anions. The systems develop into semimetals (P (3) over bar m1-Li2C2) and metals (Cmcm-Li2C2, Cmcm-CaC2, and Immm-CaC2) with polymeric anions (chains, layers, strands) at moderate pressures (below 20 GPa). Cmcm-CaC2 is energetically closely competing with the ground, state structure. Polyanionic forms of carbon 4 stabilized by electrostatic interactions with surrounding cations add a new feature to carbon chemistry. SemimetallicP (3) over bar m1-Li2C2 displays an electronic structure close to that of graphene. The pi* band, however, is hybridized with Li-sp states and changed into a bonding valence band. Metallic forms are predicted to be superconductors. Calculated critical temperatures may exceed 10 K for equilibrium volume structures.

  • 66. Benyahia, K
    et al.
    Nabi, Z
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Boukabrine, F
    Khalfi, A
    Ab-initio calculations of the optical and magnetic properties of erbium silicide ErSi22009In: Journal of Physics and Chemistry of Solids, ISSN 0022-3697, E-ISSN 1879-2553, Vol. 70, no 10, p. 1378-1384Article in journal (Refereed)
    Abstract [en]

    We present a computational method for the ab-initio study of the optical and magnetic properties using the augmented plane wave plus local orbitals (APW+lo) method. The calculations are presented within the local density (LDA) approximation. Erbium silicide (ErSi2) is representative of the whole trivalent heavy-rare-earth disilicides family, and its study will provide information valid for all of them. Thus, the study of its optical and magnetic properties is very important, especially for the calculation of magneto-optical quantities. In this paper the optical and magnetic properties are well described. Up to now no theoretical study on optical and magnetic properties of ErSi2 is available in the literature. We report theoretical calculations of the reel and imaginary parts of the dielectric function (DF), the refractive index and the extinction coefficient, the spectra of the reflectivity, the absorption coefficient, the energy-loss function (ELF), and the magnetic moments. (C) 2009 Elsevier Ltd. All rights reserved.

  • 67. Benyahia, K
    et al.
    Nabi, Z
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Khalfi, A
    Magneto-optical Kerr effect (MOKE) of the rare-earth silicide ErSi2 using ab-initio calculations2009In: Current applied physics, ISSN 1567-1739, E-ISSN 1878-1675, Vol. 9, no 5, p. 925-927Article in journal (Refereed)
    Abstract [en]

    We present a computational method for the ab-initio study of the magneto-optical quantities using the augmented plane wave plus local orbitals (APW+lo) method. The calculations are performed within the local-density (LDA) approximation. In the present paper, the optical conductivity is the basic quantity for the evaluation of the magneto-optical Kerr effect (MOKE). Thus it is well described and calculated. Considerable work has been performed on the magneto-optical Kerr effect using experiments, however, no experimental or theoretical work has been investigated on rare-earth silicide ErSi2, in particular using ab-initio method. Our results consist a prediction. (C) 2008 Elsevier B.V. All rights reserved.

  • 68. Berseth, Polly A
    et al.
    Harter, Andrew G
    Zidan, Ragaiy
    Blomqvist, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Araújo, C Moysés
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Scheicher, Ralph H
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Jena, Puru
    Carbon nanomaterials as catalysts for hydrogen uptake and release in NaAlH42009In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 9, no 4, p. 1501-1505Article in journal (Refereed)
    Abstract [en]

    A synergistic approach involving experiment and first-principles theory not only shows that carbon nanostructures can be used as catalysts for hydrogen uptake and release in complex metal hydrides such as sodium alanate, NaAlH(4), but also provides an unambiguous understanding of how the catalysts work. Here we show that the stability of NaAlH(4) originates with the charge transfer from Na to the AlH(4) moiety, resulting in an ionic bond between Na(+) and AlH(4)(-) and a covalent bond between Al and H. Interaction of NaAlH(4) with an electronegative substrate such as carbon fullerene or nanotube affects the ability of Na to donate its charge to AlH(4), consequently weakening the Al-H bond and causing hydrogen to desorb at lower temperatures as well as facilitating the absorption of H(2) to reverse the dehydrogenation reaction. In addition, based on our experimental observations and theoretical calculations it appears the curvature of the carbon nanostructure plays a role in the catalytic process. Ab initio molecular dynamics simulation further reveals the time evolution of the charge transfer process.

  • 69. Blomqvist, A.
    et al.
    Århammar, Cecilia
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Pedersen, H.
    Silvearv, Fredrik
    Norgren, S.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Understanding the catalytic effects of H(2)S on CVD-growth of alpha-alumina: Thermodynamic gas-phase simulations and density functional theory2011In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 206, no 7, p. 1771-1779Article in journal (Refereed)
    Abstract [en]

    The catalytic effect of H(2)S on the AlCl(3)/H(2)/CO(2)/HCl chemical vapor deposition (CVD) process has been investigated on an atomistic scale. We apply a combined approach with thermodynamic modeling and density functional theory and show that H(2)S acts as mediator for the oxygenation of the AI-surface which will in turn increase the growth rate of Al(2)O(3). Furthermore we suggest surface terminations for the three investigated surfaces. The oxygen surface is found to be hydrogenated, in agreement with a number of previous works. The aluminum surfaces are Cl-terminated in the studied CVD-process. Furthermore, we find that the AlClO molecule is a reactive transition state molecule which interacts strongly with the aluminum and oxygen surfaces.

  • 70. Blomqvist, A.
    et al.
    Århammar, Cecilia
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Pedersen, H.
    Silvearv, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Norgren, S.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Understanding the catalytic effects of H2S on CVD-growth of α-alumina: Thermodynamic gas-phase simulations and density functional theory2011In: Proceedings of the 38th International Conference on Metallurgical Coatings and Thin Films (ICMCTF) — ICMCTF 2011, 2011, p. 1771-1779Conference paper (Refereed)
    Abstract [en]

    The catalytic effect of H2S on the AlCl3/H2/CO2/HCl chemical vapor deposition (CVD) process has been investigated on an atomistic scale. We apply a combined approach with thermodynamic modeling and density functional theory and show that H2S acts as mediator for the oxygenation of the Al-surface which will in turn increase the growth rate of Al2O3. Furthermore we suggest surface terminations for the three investigated surfaces. The oxygen surface is found to be hydrogenated, in agreement with a number of previous works. The aluminum surfaces are Cl-terminated in the studied CVD-process. Furthermore, we find that the AlClO molecule is a reactive transition state molecule which interacts strongly with the aluminum and oxygen surfaces.

  • 71.
    Blomqvist, Andreas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Araujo, Moyses
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Scheicher, Ralph Hendrik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Srepusharawoot, Pornjuk
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Li, Wen
    Chen, Ping
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Hydrogen as promoter and inhibitor of superionicity: A case study on Li-N-H systems2010In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 82, no 2, p. 024304-Article in journal (Refereed)
    Abstract [en]

    Materials which possess a high lithium ion conductivity are very attractive for battery and fuel cell applications. Hydrogenation of the fast-ion conductor lithium nitride (Li3N) leads to the formation of lithium imide (Li2NH) and subsequently of lithium amide (LiNH2). Using ab initio molecular dynamics simulations, we carried out a comparative study of the Li diffusion in these three systems. The results demonstrate that hydrogen can work as both promoter and inhibitor of Li mobility, with the lowest transition temperature to the superionic state occurring in Li2NH. Furthermore, we show that the creation of Li vacancies strongly affects Li diffusion in Li3N, but not so in Li2NH. Finally, we explain our findings with the help of a simple model.

  • 72.
    Blomqvist, Andreas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Araújo, C. Moysés
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Jena, Puru
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Dehydrogenation from 3d-transition-metal-doped NaAlH4: Prediction of catalysts2007In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 90, no 14, p. 141904-Article in journal (Refereed)
    Abstract [en]

    A fundamental understanding of the role of catalysts in improving the kinetics and thermodynamics of hydrogen sorption in NaAlH4 is the key for using this material in hydrogen storage. The authors present a systematic theoretical study of energies needed to desorb hydrogen in 3d transition metal (Sc-Cu)-doped NaAlH4. They show that Cr and Fe atoms can be far more effective catalysts than Ti in desorbing hydrogen. The role of the 3d metal atoms in improving the thermodynamics of dehydrogenation is attributed to a significant shortening of the bond length with neighboring Al atoms.

  • 73.
    Blomqvist, Andreas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Condensed Matter Theory.
    Araújo, C. Moysés
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Condensed Matter Theory.
    Srepusharawoot, P.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Condensed Matter Theory.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Condensed Matter Theory.
    Li-decorated metal-organic framework-5: A route to achieving a suitable hydrogen storage medium2007In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 104, no 51, p. 20173-Article in journal (Refereed)
    Abstract [en]

    A significant improvement in molecular hydrogen uptake properties is revealed by our ab initio calculations for Li-decorated metal-organic framework 5. We have found that two Li atoms are strongly adsorbed on the surfaces of the six-carbon rings, one on each side, carrying a charge of +0.9e per Li atom. Each Li can cluster three H-2 molecules around itself with a binding energy of 12 kJ (mol H-2)(-1). Furthermore, we show from ab initio molecular dynamics simulations with a hydrogen loading of 18 H2 per formula unit that a hydrogen uptake of 2.9 wt % at 200 K and 2.0 wt % at 300 K is achievable. To our knowledge, this is the highest hydrogen storage capacity reported for metal-organic framework 5 under such thermodynamic conditions.

  • 74.
    Blomqvist, Andreas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Pálsson, Gunnar K.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Araujo, Moyses
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Hjörvarsson, Björgvin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Significance of self-trapping on hydrogen diffusion2010In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 105, no 18, p. 185901-Article in journal (Refereed)
    Abstract [en]

    The diffusion rate of hydrogen in Nb was calculated using ab initio molecular dynamics simulations. At low temperatures the hydrogen is strongly trapped in a local strain field which is caused by the elastic response of the lattice. At elevated temperatures, the residence time (τ) of hydrogen in an interstitial site is not sufficient for fully developing the local strain field. This unbinding of the interstitial hydrogen and the strain field increases the hopping rate (1/τ) at elevated temperatures (>400  K). These results call for a revision of the conceptual framework of diffusion of hydrogen in transition metals at elevated temperatures.

  • 75. Bouhou, S.
    et al.
    El Hamri, M.
    Essaoudi, I.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Ainane, Abdelmajid
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Magnetic properties of a single transverse Ising ferrimagnetic nanoparticle2015In: Physica. B, Condensed matter, ISSN 0921-4526, E-ISSN 1873-2135, Vol. 456, p. 142-150Article in journal (Refereed)
    Abstract [en]

    Using the effective field theory with a probability distribution technique that accounts for the self-spin correlation function, the thermal and the magnetic properties of a single Ising nanoparticle consisting of a ferromagnetic core, a ferromagnetic surface shell and a ferrimagnetic interface coupling are examined. The effect of the transverse held in the surface shell, the exchange interactions between core/shell and in surface shell on the free energy, thermal magnetization, specific heat and susceptibility are studied. A number of interesting phenomena have been found such as the existence of the compensation phenomenon and the magnetization profiles exhibit P-type, N-type and Q-type behaviors. (C) 2014 Elsevier B.V. All rights reserved.

  • 76.
    Bouhou, S.
    et al.
    Univ Moulay Ismail, Unite Associee CNRST URAC 08, LP2MS, Phys Dept,Fac Sci, BP 11201, Meknes, Morocco..
    El Hamri, M.
    Univ Moulay Ismail, Unite Associee CNRST URAC 08, LP2MS, Phys Dept,Fac Sci, BP 11201, Meknes, Morocco..
    Essaoudi, I.
    Univ Moulay Ismail, Unite Associee CNRST URAC 08, LP2MS, Phys Dept,Fac Sci, BP 11201, Meknes, Morocco.;Uppsala Univ, Dept Phys & Astron, Condensed Matter Theory Grp, S-75120 Uppsala, Sweden..
    Ainane, Abdelmajid
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Univ Moulay Ismail, Unite Associee CNRST URAC 08, LP2MS, Phys Dept,Fac Sci, BP 11201, Meknes, Morocco.;Max Planck Inst Phys Complexer Syst, Nothnitzer Str 38, D-01187 Dresden, Germany.;Univ Lorraine, LCP A2MC, Inst Chim Phys & Mat, 1 Bd Arago, F-57070 Metz, France..
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Dujardin, F.
    Univ Lorraine, LCP A2MC, Inst Chim Phys & Mat, 1 Bd Arago, F-57070 Metz, France..
    Some hysteresis loop features of 2D magnetic spin-1 Ising nanoparticle: shape lattice and single-ion anisotropy effects2017In: Zhongguó wùli xuékan, ISSN 0577-9073, Vol. 55, no 6, p. 2224-2235Article in journal (Refereed)
    Abstract [en]

    The effects of longitudinal and transverse crystal-fields on the magnetic hysteresis behaviors of 2D spin-1 Ising nanoparticles are investigated, by using the effective-field theory based on the probability distribution technique with correlations. Nanoparticles with hexagonal or square lattice are studied. A number of characteristic phenomena such as triple and quadruple hysteresis loop behaviors have been observed for certain physical parameters, originating from the competitions among the core/shell exchange interaction, anisotropies, temperature and the longitudinal magnetic field. Finally, the obtained results are compared with some experimental and theoretical results.

  • 77.
    Bouhou, S.
    et al.
    Univ Moulay Ismail, Dept Phys, Fac Sci, LP2MS, Meknes, Morocco..
    Essaoudi, I.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Univ Moulay Ismail, Dept Phys, Fac Sci, LP2MS, Meknes, Morocco.;Max Planck Inst Phys Complexer Syst, D-01187 Dresden, Germany..
    Ainane, A.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Univ Moulay Ismail, Dept Phys, Fac Sci, LP2MS, Meknes, Morocco.;Max Planck Inst Phys Complexer Syst, D-01187 Dresden, Germany..
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Investigation of a core/shell Ising nanoparticle: Thermal and magnetic properties2016In: Physica. B, Condensed matter, ISSN 0921-4526, E-ISSN 1873-2135, Vol. 481, p. 124-132Article in journal (Refereed)
    Abstract [en]

    The phase diagrams and magnetic hysteresis behavior of a spin-1/2 Ising core/shell nanoparticle are investigated by the use of the effective field theory with a probability distribution technique that accounts for the self-spin correlation functions. Nearest-neighbor pair interactions are incorporated between the Ising spins in the three parts of the nanoparticle that are core, core/shell and surface shell. The effects of the external magnetic field and core/shell exchange interaction on the thermal magnetization and susceptibility of the system are examined.

  • 78. Bouhou, S.
    et al.
    Essaoudi, I.
    Ainane, A.
    Dujardin, F.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Saber, M.
    Magnetic Properties of Diluted Magnetic Nanowire2013In: J SUPERCOND NOV MAGN, ISSN 1557-1939, Vol. 26, no 1, p. 201-211Article in journal (Refereed)
    Abstract [en]

    A magnetic diluted nanowire with cylindrical structure described by the Ising model is investigated. Using the effective field theory with a probability distribution technique, the influence of the dilution on the phase diagrams, susceptibility and the hysteresis loops are discussed in detail. Novel features are obtained for the thermal variations of longitudinal susceptibility and longitudinal magnetization. We have investigated the magnetic reversal of the system and have found the existence of triple hysteresis loops patterns, affected by the concentration of magnetic atoms, the temperature, and the exchange interaction between the core and the surface shell.

  • 79. Bouhou, S.
    et al.
    Essaoudi, I.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Ainane, A.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Oubelkacem, A.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Dujardin, F.
    Magnetic Properties of a Transverse Ising Nanoparticle2015In: Journal of Superconductivity and Novel Magnetism, ISSN 1557-1939, E-ISSN 1557-1947, Vol. 28, no 3, p. 885-890Article in journal (Refereed)
    Abstract [en]

    We use the effective field theory with a probability distribution technique to investigate the magnetic properties of an antiferromagnetic Ising core/shell nanoparticle with a negative interlayer coupling core/shell in the presence of both the longitudinal and the transverse fields. Nearest-neighbor pair interactions are incorporated between the Ising spins in three parts that are core, core/shell, and surface shell. The effects of the external and the transverse fields and the exchange interactions between core/shell and in surface shell on the hysteresis loops and the susceptibility of the nanoparticle are examined. A number of interesting phenomena have been found.

  • 80. Bouhou, S.
    et al.
    Essaoudi, I.
    Ainane, A.
    Saber, M.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Dujardin, F.
    Phase diagrams of diluted transverse Ising nanowire2013In: Journal of Magnetism and Magnetic Materials, ISSN 0304-8853, E-ISSN 1873-4766, Vol. 336, p. 75-82Article in journal (Refereed)
    Abstract [en]

    In this paper, the phase diagrams of diluted Ising nanowire consisting of core and surface shell coupling by J(cs) exchange interaction are studied using the effective field theory with a probability distribution technique, in the presence of transverse fields in the core and in the surface shell. We find a number of characteristic phenomena. In particular, the effect of concentration c of magnetic atoms, the exchange interaction core/shell, the exchange in surface and the transverse fields in core and in surface shell of phase diagrams are investigated.

  • 81. Bouhou, S.
    et al.
    Zaim, A.
    Ainane, A.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Kerouad, M.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Magnetic properties of a ferromagnetic thin film with four spin interaction: A Monte Carlo simulation study2013In: Journal of Magnetism and Magnetic Materials, ISSN 0304-8853, E-ISSN 1873-4766, Vol. 339, p. 127-132Article in journal (Refereed)
    Abstract [en]

    Monte Carlo simulation has been used to study the critical behaviors and the magnetic properties of a ferromagnetic thin Ising film with a plaquette four spin interaction. The effects of the ratio r(s) =J(s)/J of the surface exchange interaction to the bulk one and the four spin interaction on phase diagrams are investigated. A number of characteristic behaviors have been found, which include the first-and second-order phase transitions, thus also the tricritical points, triple point and isolated critical point. 

  • 82.
    Bouibes, A.
    et al.
    Université de Lille 1 Sciences et Technologies, Polytech'Lille, LGCgE-Lille Nord de France.
    Zaoui, A.
    Université de Lille 1 Sciences et Technologies, Polytech'Lille, LGCgE-Lille Nord de France.
    Luo, Wei
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Promising optical characteristics of zinc peroxide from first-principles investigation2017In: Solid State Communications, ISSN 0038-1098, E-ISSN 1879-2766, Vol. 263, p. 6-9Article in journal (Refereed)
    Abstract [en]

    The structural, electronic and optical properties of zinc peroxide have been investigated using first principle pseudopotential method within generalized gradient approximation (GGA) proposed by Perdew-Burke-Ernzerhof (PBE) and also within Heyd-Scuseria-Ernzerhof (HSE06) hybrid functional for the exchangecorrelation. An underestimated band gap (1.77 eV) along with the higher density of states and expanded energy bands around the Fermi level is obtained. The HSE06 approach corrects the band gap and allows a proper description of defects with energy levels close to the conduction band. According to the HSE06 calculations, the obtained band gap is 3.2 eV. This value is very close to semiconductors band gap such as TiO2 (3.1 eV). The dielectric constants are identified with respect to electronic band structure and are utilized to derive the other optical properties such as retractive index, energy loss function, reflectivity and absorption. This mainly shows that zinc peroxide is a poor absorber of visible light.

  • 83. Bououdina, M.
    et al.
    Oumellal, Y.
    Dupont, L.
    Aymard, L.
    Al-Gharni, H.
    Al-Hajry, A.
    Maark, T. A.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    De Sarkar, A.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Deshpande, M. D.
    Qian, Z.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Rahane, A. B.
    Lithium storage in amorphous TiNi hydride: Electrode for rechargeable lithium-ion batteries2013In: Materials Chemistry and Physics, ISSN 0254-0584, E-ISSN 1879-3312, Vol. 141, no 1, p. 348-354Article in journal (Refereed)
    Abstract [en]

    In this study, amorphous TiNi phase was successfully prepared using mechanically milling for a very short time of 8 h. HRTEM confirms the formation of amorphous phase with the presence of nanocrystalline Fe particles. After hydrogenation (30 bars of H-2 for a duration of 2 h), the electrochemical reaction shows that TiNi hydride/Li cell discharges at a current of one Li for 10 h between 3 V and 0.005 V. The discharge of TiNiH electrode around x = 1 Li corresponds to a capacity of 251 mAh g(-1) and a hydride composition of TiNiH1.0 at an average voltage of 0.4 V. Ex-situ X-ray diffraction pattern collected at the end of the discharge shows a mixture of amorphous TiNi compound and LiH. A general mechanism for the electrochemical reaction is then proposed: alpha-TiNiH + Li+ + e(-) -> alpha-TiNi + LiH. The results from DFT calculations yield an average cell voltage of 0.396 V, which is in good agreement with the experimental pseudo-plateau occurring at 0.4 V.

  • 84. Boye, S.A
    et al.
    Lazor, P
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Ahuja, R
    Physics, Department of Physics. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Magnetoresistance and Hall effect measurements of Ni to 6 GPa2005In: Journal of Magnetism and Magnetic Materials, Vol. 294, p. 347-358Article in journal (Refereed)
  • 85.
    Boye, S.A
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Lazor, P
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Ahuja, R
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Magnetoresistance and Hall-effect measurements of Ni thin films2005In: Journal of Applied Physics, Vol. 97, p. 083902:1-5Article in journal (Refereed)
  • 86.
    Callini, Elsa
    et al.
    EPFL Valais Wallis Swiss Fed Inst Technol, LMER, Rue Ind 17, CH-1950 Sion, Switzerland.;Swiss Fed Lab Mat Sci & Technol, Empa, Ueberlandstr 129, CH-8600 Dubendorf, Switzerland..
    Aguey-Zinsou, Kondo-Francois
    Univ New S Wales, Sch Chem Engn, MERLin Grp, Sydney, NSW 2052, Australia..
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Royal Inst Technol KTH, Dept Mat & Engn, Appl Mat Phys, S-10044 Stockholm, Sweden..
    Ramon Ares, Jose
    Univ Autonoma Madrid, Fac Ciencias, Dpto Fis Mat, Grp Mire, E-28049 Madrid, Spain..
    Bals, Sara
    Univ Antwerp, Dept Phys, EMAT, Groenenborgerlaan 171, B-2020 Antwerp, Belgium..
    Biliskov, Nikola
    Rudjer Boskovic Inst, Bijenicka Cesta 54, Zagreb 10000, Croatia..
    Chakraborty, Sudip
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Charalambopoulou, Georgia
    Natl Ctr Sci Res Demokritos, Athens 15341, Greece..
    Chaudhary, Anna-Lisa
    Helmholtz Zentrum Geesthacht, Inst Mat Res, Dept Nanotechnol, Max Planck Str 1, Geesthacht, Germany..
    Cuevas, Fermin
    UPEC, CNRS, ICMPE, UMR7182, 2-8 Rue Henri Dunant, F-94320 Thiais, France..
    Dam, Bernard
    Delft Univ Technol, Chem Engn, Julianalaan 136, NL-2628 BL Delft, Netherlands..
    de Jongh, Petra
    Univ Utrecht, Debye Inst Nanomat Sci, Inorgan Chem & Catalysis, Univ Weg 99, NL-3584 CG Utrecht, Netherlands..
    Dornheim, Martin
    Helmholtz Zentrum Geesthacht, Inst Mat Res, Dept Nanotechnol, Max Planck Str 1, Geesthacht, Germany..
    Filinchuk, Yaroslav
    Catholic Univ Louvain, Inst Condensed Matter & Nanosci, B-1348 Louvain, Belgium..
    Novakovic, Jasmina Grbovic
    Univ Belgrade, Vinca Inst Nucl Sci, POB 522, Belgrade 1000, Serbia..
    Hirscher, Michael
    Max Planck Inst Intelligent Syst Stuttgart, Heisenbergstr 3, D-70569 Stuttgart, Germany..
    Jensen, Torben R.
    Aarhus Univ, Dept Chem, Ctr Mat Crystallog, Langelandsgade 140, DK-8000 Aarhus C, Denmark.;Aarhus Univ, iNANO, Langelandsgade 140, DK-8000 Aarhus C, Denmark..
    Jensen, Peter Bjerre
    Tech Univ Denmark, Dept Energy Convers & Storage, Fysikvej,Bldg 309, DK-2800 Lyngby, Denmark..
    Novakovic, Nikola
    Univ Belgrade, Vinca Inst Nucl Sci, POB 522, Belgrade 1000, Serbia..
    Lai, Qiwen
    Univ New S Wales, Sch Chem Engn, MERLin Grp, Sydney, NSW 2052, Australia..
    Leardini, Fabrice
    Univ Autonoma Madrid, Fac Ciencias, Dpto Fis Mat, Grp Mire, E-28049 Madrid, Spain..
    Gattia, Daniele Mirabile
    Res Ctr Casaccia, ENEA, Dept Phys Methods & Mat, Via Anguillarese 301, Rome, Italy..
    Pasquini, Luca
    Alma Mater Studiorum Univ Bologna, Dept Phys & Astron, I-40127 Bologna, Italy..
    Steriotis, Theodore
    Natl Ctr Sci Res Demokritos, Athens 15341, Greece..
    Turner, Stuart
    Univ Antwerp, Dept Phys, EMAT, Groenenborgerlaan 171, B-2020 Antwerp, Belgium..
    Vegge, Tejs
    Tech Univ Denmark, Dept Energy Convers & Storage, Fysikvej,Bldg 309, DK-2800 Lyngby, Denmark..
    Zuttel, Andreas
    EPFL Valais Wallis Swiss Fed Inst Technol, LMER, Rue Ind 17, CH-1950 Sion, Switzerland..
    Montone, Amelia
    Res Ctr Casaccia, ENEA, Dept Phys Methods & Mat, Via Anguillarese 301, Rome, Italy..
    Nanostructured materials for solid-state hydrogen storage: A review of the achievement of COST Action MP11032016In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 41, no 32, p. 14404-14428Article in journal (Refereed)
    Abstract [en]

    In the framework of the European Cooperation in Science and Technology (COST) Action MP1103 Nanostructured Materials for Solid-State Hydrogen Storage were synthesized, characterized and modeled. This Action dealt with the state of the art of energy storage and set up a competitive and coordinated network capable to define new and unexplored ways for Solid State Hydrogen Storage by innovative and interdisciplinary research within the European Research Area. An important number of new compounds have been synthesized: metal hydrides, complex hydrides, metal halide ammines and amidoboranes. Tuning the structure from bulk to thin film, nanoparticles and nanoconfined composites improved the hydrogen sorption properties and opened the perspective to new technological applications. Direct imaging of the hydrogenation reactions and in situ measurements under operando conditions have been carried out in these studies. Computational screening methods allowed the prediction of suitable compounds for hydrogen storage and the modeling of the hydrogen sorption reactions on mono-, bi-, and three-dimensional systems. This manuscript presents a review of the main achievements of this Action.

  • 87.
    Chafai, A.
    et al.
    Univ Moulay Ismail, Phys Dept, Fac Sci, Unite Associee CNRST URAC 08,LP2MS, Meknes, Morocco..
    Dujardin, F.
    Univ Lorraine, LCP A2MC, Inst Chim Phys & Mat, 1 Bd Arago, F-57070 Metz, France..
    Essaoudi, I.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Univ Moulay Ismail, Phys Dept, Fac Sci, Unite Associee CNRST URAC 08,LP2MS, Meknes, Morocco.
    Ainane, A.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Univ Moulay Ismail, Phys Dept, Fac Sci, Unite Associee CNRST URAC 08,LP2MS, Meknes, Morocco.;Univ Lorraine, LCP A2MC, Inst Chim Phys & Mat, 1 Bd Arago, F-57070 Metz, France.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Shallow donor inside core/shell spherical nanodot: Effect of nanostructure size and dielectric environment on energy spectrum2017In: Superlattices and Microstructures, ISSN 0749-6036, E-ISSN 1096-3677, Vol. 111, p. 976-982Article in journal (Refereed)
    Abstract [en]

    We have reported the impact of the core and shell radii on the energy spectrum of centered shallow donor confined inside CdSe/ZnTe core/shell quantum dot and ZnTe/CdSe inverted core/shell quantum dot. The dielectric discontinuity between the nanosystems and their surrounding medium was considered. In order to examine the behavior of the donor binding energy as a function of the spatial parameters a variational approach within the framework of the effective-mass approximation was deployed. Our model shows that for a fixed shell radius the increase of the core radius value blue-shifts the binding energy of the donor inside inverted core/shell quantum dot only if the value of the core to shell radii ratio is between 0.9 and 1, otherwise it is red-shifted. By contrast, for core/shell quantum dot system the binding energy is red-shifted by increasing the core radius for a fixed nanostructure size and for all values of the core to shell radii ratio. We have also found that the donor binding energy values are more important in a core/shell nanodot than in an inverted core/shell quantum dot.

  • 88.
    Chafai, A.
    et al.
    Univ Moulay Ismail, Phys Dept, Unite Associee CNRST URAC 08, Lab Phys Mat & Modelisat Syst,LP2MS,Fac Sci, BP 11201, Meknes, Morocco..
    Essaoudi, I.
    Univ Moulay Ismail, Phys Dept, Unite Associee CNRST URAC 08, Lab Phys Mat & Modelisat Syst,LP2MS,Fac Sci, BP 11201, Meknes, Morocco.;Uppsala Univ, Dept Phys & Astron, Condensed Matter Theory Grp, S-75120 Uppsala, Sweden..
    Ainane, A.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Dujardin, F.
    Univ Lorraine, LCP A2MC, Inst Chim Phys & Mat, 1 Bd Arago, F-57070 Metz, France..
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Tuning the binding energy of on-center donor in CdSe/ZnTe core/shell quantum dot by spatial parameters and magnetic field strength2017In: Physica. E, Low-Dimensional systems and nanostructures, ISSN 1386-9477, E-ISSN 1873-1759, Vol. 94, p. 96-99Article in journal (Refereed)
    Abstract [en]

    The behavior of the electron ground state and of the ground state binding energy of an on-center donor confined in a CdSe/ZnTe core/shell spherical nanodot was examined theoretically within the framework of the effectivemass approximation and using a variational calculation. The radial dependence of the dielectric constant and of the electron effective mass as well as the effect of the polarization charge were considered. Our results highlight the large impact of the magnetic field strength and the spatial parameters on the energy behavior for both the electron and the donor. Our study points out also the fact that the magnetic confinement may be eclipsed by the spatial confinement in heteronanostructures with small size and expected to be dominant in the opposite case.

  • 89.
    Chakraborty, Sudip
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Xie, Wei
    Univ Calif Berkeley, Dept Mat Sci & Engn, Berkeley, CA 94720 USA..
    Mathews, Niripan
    Nanyang Technol Univ, Sch Mat Sci & Engn, Nanyang Ave, Singapore 639798, Singapore.;ERI N, Res Techno Plaza,X Frontier Block,Level 5, Singapore 637553, Singapore..
    Sherburne, Matthew
    Univ Calif Berkeley, Dept Mat Sci & Engn, Berkeley, CA 94720 USA..
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Asta, Mark
    Univ Calif Berkeley, Dept Mat Sci & Engn, Berkeley, CA 94720 USA..
    Mhaisalkar, Subodh G.
    Nanyang Technol Univ, Sch Mat Sci & Engn, Nanyang Ave, Singapore 639798, Singapore.;ERI N, Res Techno Plaza,X Frontier Block,Level 5, Singapore 637553, Singapore..
    Rational Design: A High-Throughput Computational Screening and Experimental Validation Methodology for Lead-Free and Emergent Hybrid Perovskites2017In: ACS ENERGY LETTERS, ISSN 2380-8195, Vol. 2, no 4, p. 837-845Article in journal (Refereed)
    Abstract [en]

    Perovskite solar cells, with efficiencies of 22.1%, are the only solution-processable technology to outperform multicrystalline silicon and thin-film solar cells. Whereas substantial progress has been made in scalability and stability, toxicity concerns drive the need for lead replacement, intensifying research into the broad palette of elemental substitutions, solid solutions, and multidimensional structures. Perovskites have gone from comprising three to more than eight (CH3NH3, HC(NH2)(2), Cs, Rb, Pb, Sn, I, Br) organic and inorganic constituents, and a variety of new embodiments including layered, double perovskites, and metal-deficient perovskites are being explored. Although most experimentation is guided by intuition and trial-and-error-based Edisonian approaches, rational strategies underpinned by computational screening and targeted experimental validation are emerging. In addressing emergent perovskites, this perspective discusses the rational design methodology leveraging density functional theory-based high-throughput computational screening coupled to downselection strategies to accelerate the discovery of materials and industrialization of perovskite solar cells.

  • 90.
    Cheng, Kai
    et al.
    Dalian Univ Technol, Minist Educ, Key Lab Mat Modificat Laser Ion & Electron Beams, Dalian 116024, Peoples R China.
    Guo, Yu
    Dalian Univ Technol, Minist Educ, Key Lab Mat Modificat Laser Ion & Electron Beams, Dalian 116024, Peoples R China.
    Han, Nannan
    Dalian Univ Technol, Minist Educ, Key Lab Mat Modificat Laser Ion & Electron Beams, Dalian 116024, Peoples R China.
    Jiang, Xue
    Dalian Univ Technol, Minist Educ, Key Lab Mat Modificat Laser Ion & Electron Beams, Dalian 116024, Peoples R China.
    Zhang, Junfeng
    Shanxi Normal Univ, Sch Phys & Informat Engn, Linfen 041000, Peoples R China.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Su, Yan
    Dalian Univ Technol, Minist Educ, Key Lab Mat Modificat Laser Ion & Electron Beams, Dalian 116024, Peoples R China.
    Zhao, Jijun
    Dalian Univ Technol, Minist Educ, Key Lab Mat Modificat Laser Ion & Electron Beams, Dalian 116024, Peoples R China.
    2D lateral heterostructures of group-III monochalcogenide: Potential photovoltaic applications2018In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 112, no 14, article id 143902Article in journal (Refereed)
    Abstract [en]

    Solar photovoltaics provides a practical and sustainable solution to the increasing global energy demand. Using first-principles calculations, we investigate the energetics and electronic properties of two-dimensional lateral heterostructures by group-III monochalcogenides and explore their potential applications in photovoltaics. The band structures and formation energies from supercell calculations demonstrate that these heterostructures retain semiconducting behavior and might be synthesized in laboratory using the chemical vapor deposition technique. According to the computed band offsets, most of the heterojunctions belong to type II band alignment, which can prevent the recombination of electron-hole pairs. Besides, the electronic properties of these lateral heterostructures can be effectively tailored by the number of layers, leading to a high theoretical power conversion efficiency over 20%.

  • 91.
    Choudhuri, Indrani
    et al.
    Indian Inst Technol, Sch Basic Sci, Discipline Chem, Indore 452020, Madhya Pradesh, India..
    Patra, Nandini
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Indian Inst Technol, Ctr Mat Sci & Engn, Indore 452020, Madhya Pradesh, India..
    Mahata, Arup
    Indian Inst Technol, Sch Basic Sci, Discipline Chem, Indore 452020, Madhya Pradesh, India..
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Royal Inst Technol KTH, Dept Mat Sci & Engn, Appl Mat Phys, S-10044 Stockholm, Sweden..
    Pathak, Biswarup
    Indian Inst Technol, Sch Basic Sci, Discipline Chem, Indore 452020, Madhya Pradesh, India.;Indian Inst Technol, Ctr Mat Sci & Engn, Indore 452020, Madhya Pradesh, India..
    B-N@Graphene: Highly Sensitive and Selective Gas Sensor2015In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 119, no 44, p. 24827-24836Article in journal (Refereed)
    Abstract [en]

    We have performed density functional theory (DFT) calculations to study the gas (CO, CO2, NO, and NO2) sensing mechanism of pure and doped (B@, N@, and B-N@) graphene surfaces. The calculated adsorption energies of the various toxic gases (CO, CO2, NO, and NO2) on the pure and doped graphene surfaces show, doping improves adsorption energy and selectivity. The electronic properties of the B-N@graphene surfaces change significantly compared to pure and B@ and N@graphene surfaces, while selective gas molecules are adsorbed. So, we report B-N codoping on graphene can be highly sensitive and selective for semiconductor-based gas sensor.

  • 92.
    Colarieti-Tosti, M.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Simak, S. I.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Nordström, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Åberg, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Condensed Matter Theory.
    Edvardsson, S.
    Brooks, Michael S. S.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Origin of Magnetic Anisotropy of Gd Metal2003In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 91, no 15, p. 157201-157204Article in journal (Refereed)
    Abstract [en]

    Using first-principles theory, we have calculated the energy of Gd as a function of spin direction, θ, between the c and a axes and found good agreement with experiment for both the total magnetic anisotropy energy and its angular dependence. The calculated low temperature direction of the magnetic moment lies at an angle of 20° to the c axis. The calculated magnetic anisotropy energy of Gd metal is due to a unique mechanism involving a contribution of 7.5  μeV from the classical dipole-dipole interaction between spins plus a contribution of 16  μeV due to the spin-orbit interaction of the conduction electrons. The 4f spin polarizes the conduction electrons via exchange interaction, which transfers the magnetic anisotropy of the conduction electrons to the 4f spin.

  • 93.
    Colarieti-Tosti, Massimiliano
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics IV. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Theoretical Magnetism.
    Simak, Sergei
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics IV. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Theoretical Magnetism.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics IV. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Theoretical Magnetism.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics IV. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Theoretical Magnetism.
    Nordström, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics IV. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Theoretical Magnetism.
    Edwardsson, Sverker
    Brooks, Michael
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics IV. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Theoretical Magnetism.
    On the magnetic anisotropy of Gd metal2003In: Physical Review Letters, Vol. 91, p. 157201-Article in journal (Refereed)
  • 94.
    Cricchio, F
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics.
    Ahuja, Rajeev
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics.
    High Pressure melting of Lead2006In: Phys. Rev. B, Vol. 73, p. 140103-Article in journal (Refereed)
  • 95.
    Dahlstrand, Christian
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC.
    Jahn, Burkhard O.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC.
    Grigoriev, Anton
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Villaume, Sebastien
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Ottosson, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC.
    Polyfulvenes: Polymers with "Handles" That Enable Extensive Electronic Structure Tuning2015In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 119, no 46, p. 25726-25737Article in journal (Refereed)
    Abstract [en]

    The fundamental electronic structure properties of substituted poly(penta)fulvenes and pentafulvene-based polymers are analyzed through qualitative molecular orbital (MO) theory combined with calculations at the B3LYP and HSE06 hybrid density functional theory (DFT) levels. We argue that the pentafulvene monomer unit has a unique character because electron density in the exocyclic C=C double bond can be polarized into and out of the five-membered ring, a feature that is not available to other more commonly used monomers. It is investigated how the energy gaps between the highest occupied and lowest unoccupied molecular orbitals (HOMO and LUMO, respectively), as approximate band gaps, are influenced by exocyclic substitution, introduction of linker groups, benzannulation, and ring substitution. In particular, the exocyclic positions of the fulvene act as handles by which the electronic structure of the polymer can be tuned between the quinoid and fulvenoid valence bond isomers; electron-withdrawing exocyclic substituents lead to polyfulvenes in the quinoid form while those with electron-donating substituents prefer the fulvenoid. Taken together, the HOMO-LUMO gaps of polyfulvenes can be tuned extensively, varying in ranges 0.77-2.44 eV (B3LYP) and 0.35-2.00 eV (HSE06) suggesting that they are a class of polymers with highly interesting, yet nearly unexplored, properties.

  • 96. Dallera, C.
    et al.
    Wessely, Ola
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Colarieti-Tosti, M.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Johansson, Börje
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Katsnelson, M. I.
    Annese, E.
    Rueff, J.-P.
    Vank'o, G.
    Braicovich, L.
    Grioni, M.
    Understanding mixed valent materials: Effects of dynamical core-hole screening in high-pressure x-ray spectroscopy2006In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 74, no 8, p. 081101-Article in journal (Refereed)
    Abstract [en]

    Changes in the electronic structure of Yb, a material whose valence is modified under pressure, are observed with remarkable detail in x-ray absorption and emission data measured between ambient conditions and 20 GPa. These changes are reproduced by a theory that essentially does not rely on experimental parameters, and includes dynamical core-hole screening. From the combined experimental and theoretical data we can firmly establish on a quantitative level how the valency of an intermediate valence material is modified by pressure. In metallic Yb it increases from 2 to 2.55 +/- 0.05 between 0 and 20 GPa.

  • 97.
    Das, Suman
    et al.
    Indian Inst Sci, Solid State & Struct Chem Unit, Bengaluru 560012, India..
    Swain, Diptikanta
    Indian Inst Sci, Solid State & Struct Chem Unit, Bengaluru 560012, India..
    Araujo, Rafael Barros Neves de
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Shi, Songxin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Beihang Univ, Sch Mat Sci & Engn, Beijing 100191, Peoples R China..
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Royal Inst Technol KTH, Dept Mat & Engn, Appl Mat Phys, S-10044 Stockholm, Sweden..
    Row, Tayur N. Guru
    Indian Inst Sci, Solid State & Struct Chem Unit, Bengaluru 560012, India..
    Bhattacharyya, Aninda J.
    Indian Inst Sci, Solid State & Struct Chem Unit, Bengaluru 560012, India..
    Alloying in an Intercalation Host: Metal Titanium Niobates as Anodes for Rechargeable Alkali-Ion Batteries2018In: Chemistry - An Asian Journal, ISSN 1861-4728, E-ISSN 1861-471X, Vol. 13, no 3, p. 299-310Article in journal (Refereed)
    Abstract [en]

    We discuss here a unique flexible non-carbonaceous layered host, namely, metal titanium niobates (M-Ti-niobate, M: Al3+, Pb2+, Sb3+, Ba2+, Mg2+), which can synergistically store both lithium ions and sodium ions via a simultaneous intercalation and alloying mechanisms. M-Ti-niobate is formed by ion exchange of the K+ ions, which are specifically located inside galleries between the layers formed by edge and corner sharing TiO6 and NbO6 octahedral units in the sol-gel synthesized potassium titanium niobate (KTiNbO5). Drastic volume changes (approximately 300-400%) typically associated with an alloying mechanism of storage are completely tackled chemically by the unique chemical composition and structure of the M-Ti-niobates. The free space between the adjustable Ti/Nb octahedral layers easily accommodates the volume changes. Due to the presence of an optimum amount of multivalent alloying metal ions (50-75% of total K+) in the M-Ti-niobate, an efficient alloying reaction takes place directly with ions and completely eliminates any form of mechanical degradation of the electroactive particles. The M-Ti-niobate can be cycled over a wide voltage range (as low as 0.01V) and displays remarkably stable Li+ and Na+ ion cyclability (>2 Li+/Na+ per formula unit) for widely varying current densities over few hundreds to thousands of successive cycles. The simultaneous intercalation and alloying storage mechanisms is also studied within the density functional theory (DFT) framework. DFT expectedly shows a very small variation in the volume of Al-titanium niobate following lithium alloying. Moreover, the theoretical investigations also conclusively support the occurrence of the alloying process of Li ions with the Al ions along with the intercalation process during discharge. The M-Ti-niobates studied here demonstrate a paradigm shift in chemical design of electrodes and will pave the way for the development of a multitude of improved electrodes for different battery chemistries.

  • 98.
    de Almeida, J. S.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Kim, D. Y.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Ortiz, C.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Klintenberg, Mattias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    On the dynamical stability and metallic behavior of YH3 under pressure2009In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 94, no 25, p. 251913-Article in journal (Refereed)
    Abstract [en]

    Wereport on the behavior of structural and electronic properties ofyttrium trihydride under pressure using first principles calculations. We showthat YH3 undergoes a structural transformation and its high pressurephase is dynamically stable under pressure since the peak atthe imaginary frequencies of the phonon density of states, whichaccount for the structural instability disappears at high pressure. Additionally,our GW calculations indicate a metallization of the high pressurecubic phase of YH3.

  • 99. De Sarkar, Abir
    et al.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Electronic charge transport through ZnO nanoribbons2014In: Journal of Physics and Chemistry of Solids, ISSN 0022-3697, E-ISSN 1879-2553, Vol. 75, no 11, p. 1223-1228Article in journal (Refereed)
    Abstract [en]

    I-V characteristics of ZnO nanoribbons (NRs) have been investigated using density functional theory coupled to non-equilibrium Green's Function. The current through the NRs drops with the increasing NR width, leveling off to 1.66 and 0.42 mu A in zig-zag and arm-chair NRs respectively for widths similar to 20 angstrom at 3 V of electrical bias. The transconductance as well as the current flowing through the arm-chair NRs decays exponentially with NR width for both odd and even number of dimer lines traversed. The current through the zig-zag NRs falls off exponentially with NR width, being insensitive to the odd or even numbers of zig-zag lines appearing along the normal to the charge transport direction.

  • 100. Dera, Przemyslaw
    et al.
    Nisar, Jawad
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Tkachev, Sergey
    Prakapenka, Vitali B.
    New type of possible high-pressure polymorphism in NiAs minerals in planetary cores2013In: Physics and chemistry of minerals, ISSN 0342-1791, E-ISSN 1432-2021, Vol. 40, no 2, p. 183-193Article in journal (Refereed)
    Abstract [en]

    The nickel arsenide (B8(1)) and related crystal structures are among the most important crystallographic arrangements assumed by Fe and Ni compounds with light elements such as Si, O, S, and P, expected to be present in planetary cores. Despite the simple structure, some of these materials like troilite (FeS) exhibit complex phase diagrams and rich polymorphism, involving significant changes in interatomic bonding and physical properties. NiP (oP16) represents one of the two principal structure distortions found in the nickel arsenide family and is characterized by P-P bonding interactions that lead to the formation of P-2 dimers. In the current study, the single-crystal synchrotron X-ray diffraction technique, aided by first principles density functional theory (DFT) calculations, has been applied to examine the compression behavior of NiP up to 30 GPa. Two new reversible displacive phase transitions leading to orthorhombic high-pressure phases with Pearson symbols oP40 and oC24 were found to occur at approximately 8.5 and 25.0 GPa, respectively. The oP40 phase has the primitive Pnma space group with unit cell a = 4.7729(5) , b = 16.6619(12) , and c = 5.8071(8) at 16.3(1) GPa and is a superstructure of the ambient oP16 phase with multiplicity of 2.5. The oC24 phase has the acentric Cmc2(1) space group with unit cell a = 9.695(6) , b = 5.7101(9) , and c = 4.7438(6) at 28.5(1) GPa and is a superstructure of the oP16 phase with multiplicity of 1.5. DFT calculations fully support the observed sequence of phase transitions. The two new phases constitute logical next stages of P sublattice polymerization, in which the dilution of the P-3 units, introduced in the first high-pressure phase, decreases, leading to compositions of Ni-20(P-3)(4)(P-2)(4) and Ni-12(P-3)(4), and provide important clues to understanding of phase relations and transformation pathways in the NiAs family.

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