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  • 151.
    Fang, C.M.
    et al.
    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.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Li, S.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Wilhelmsson, Ola
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Hultman, L.
    General trend of the mechanical properties of the ternary carbides M3SiC2 (M=transition metal)2006In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 74, no 5, p. 054106-Article in journal (Refereed)
    Abstract [en]

    We present results from first-principles calculations of ternary transition metal carbides in the M3SiC2 series (where M=early transition metal). We predict structural and mechanical properties of these new MN+1AXN phases. The bulk modulus of the ternary carbides, M3SiC2, are in the calculations found to be proportional to the bulk modulus of the corresponding binary carbides, MC. We have analyzed this behavior using a simple, nearest-neighbor bond model, as well as from first-principles total energy calculations and have found that it is caused by a considerably weaker M-Si bond compared to the M-C bond.

  • 152.
    G.E. Grechnev,
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics IV. Theoretical Magnetism. TEORETISK MAGNETISM.
    Ahuja, Rajeev
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics IV. Theoretical Magnetism. Kondenserade materiens teori.
    Johansson, Börje
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics IV. Theoretical Magnetism. Kondenserade materiens teori.
    Eriksson, Olle
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics IV. Theoretical Magnetism. Teoretisk magnetism.
    Electronic structure and magnetic properties of Lithium manganese spinels2003In: J.Magn. Magn. Matt., Vol. 258, p. 285-Article in journal (Refereed)
    Abstract [en]

    Electronic and magnetic structures of the spinel-type lithium–manganese oxides LixMn2O4, x=0,0.5,1, are studied ab initio by employing a full-potential LMTO method. The effect of the orthorhombic distortion on electronic structure and magnetism of LiMn2O4 was investigated, and our calculations do not show a substantial charge ordering at the structural transition from the cubic spinel to the orthorhombic structure.

  • 153. Glans, P. -A
    et al.
    Learmonth, T.
    Smith, K. E.
    Ferro, S.
    De Battisti, A.
    Mattesini, M.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Guo, J. -H
    Electronic structure of boron doped diamond: An x-ray spectroscopic study2013In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 102, no 16, p. 162103-Article in journal (Refereed)
    Abstract [en]

    The valence and conduction band electronic structure of boron-doped diamond has been measured using soft x-ray emission and absorption spectroscopy. The experimental results reveal p-type doping in the diamond film through the appearance of states in the band-gap. Structure distortion was observed around the doping center, while the long range order of the diamond structure remains. A chemically shifted C 1s level explains why one of the absorption features seems to appear below the valence band maximum. An excitonic feature was observed in the boron-doped diamond, similar to that observed in pure diamond, indicating that the exciton binding energy remains the same upon B-doping. 

  • 154.
    Gond, Ritambhara
    et al.
    Indian Inst Sci, Bangalore .
    Meena, Sher Singh
    Bhabha Atom Res Ctr, Bombay .
    Yusuf, S. M.
    Bhabha Atom Res Ctr, Bombay .
    Shukla, Vivekanand
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Jena, Naresh K.
    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.
    Okada, Shigeto
    Kyushu Univ, Japan.
    Barpanda, Prabeer
    Indian Inst Sci, Bangalore.
    Enabling the Electrochemical Activity in Sodium Iron Metaphosphate [NaFe(PO3)(3)] Sodium Battery Insertion Material: Structural and Electrochemical Insights2017In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 56, no 10, p. 5918-5929Article in journal (Refereed)
    Abstract [en]

    Sodium-ion batteries are widely pursued as an economic alternative to lithium-ion battery technology, where Fe- and Mn-based compounds are particularly attractive owing to their elemental abundance. Pursuing phosphate-based polyanionic chemistry, recently solid-state prepared NaFe(PO3)(3) metaphosphate was unveiled as a novel potential sodium insertion material, although it was found to be electrochemically inactive. In the current work, employing energy-savvy solution combustion synthesis, NaFe2+(PO3)(3) was produced from low-cost Fe3+ precursors. Owing to the formation of nanoscale carbon-coated product, electrochemical activity was enabled in NaFe(PO3)(3) for the first time. In congruence with the first principles density functional theory (DFT) calculations, an Fe3+/Fe2+ redox activity centered at 2.8 V (vs Na/Na+) was observed. Further, the solid-solution metaphosphate family Na(Fe1-xMnx)(PO3)(3) (x = 0-1) was prepared for the first time. Their structure and distribution of transition metals (TM = Fe/Mn) was analyzed with synchrotron diffraction, X-ray photoelectron spectroscopy, and Mossbauer spectroscopy. Synergizing experimental and computational tools, NaFe(PO3)(3) metaphosphate is presented as an electrochemically active sodium insertion host material.

  • 155. Gowtham, S.
    et al.
    Scheicher, Ralph H.
    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.
    Pandey, Ravindra
    Karna, Shashi P.
    Physisorption of nucleobases on graphene: Density-functional calculations2007In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 76, no 3, p. 033401-Article in journal (Refereed)
    Abstract [en]

    We report the results of our first-principles investigation on the interaction of the nucleobases adenine (A), cytosine (C), guanine (G), thymine (T), and uracil (U) with graphene, carried out within the density-functional theory framework, with additional calculations utilizing Hartree-Fock plus second-order Møller-Plesset perturbation theory. The calculated binding energy of the nucleobases shows the following hierarchy: G>A~T~C>U, with the equilibrium configuration being rather similar for all five of them. Our results clearly demonstrate that the nucleobases exhibit significantly different interaction strengths when physisorbed on graphene. The stabilizing factor in the interaction between the base molecule and graphene sheet is dominated by the molecular polarizability that allows a weakly attractive dispersion force to be induced between them. The present study represents a significant step toward a first-principles understanding of how the base sequence of DNA can affect its interaction with carbon nanotubes, as observed experimentally.

  • 156. Gowtham, S.
    et al.
    Scheicher, Ralph H.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Condensed Matter Theory.
    Pandey, Ravindra
    Karna, Shashi P.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Condensed Matter Theory.
    First-principles study of physisorption of nucleic acid bases on small-diameter carbon nanotubes2008In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 19, no 12, p. 125701-Article in journal (Refereed)
    Abstract [en]

    We report the results of our first-principles study based on density functional theory on the interaction of the nucleic acid base molecules adenine (A), cytosine (C), guanine (G), thymine (T), and uracil (U), with a single-walled carbon nanotube (CNT). Specifically, the focus is on the physisorption of base molecules on the outer wall of a (5, 0) metallic CNT possessing one of the smallest diameters possible. Compared to the case for CNTs with large diameters, the physisorption energy is found to be reduced in the high-curvature case. The base molecules exhibit significantly different interaction strengths and the calculated binding energies follow the hierarchy G>A>T>C>U, which appears to be independent of the tube curvature. The stabilizing factor in the interaction between the base molecule and CNT is dominated by the molecular polarizability that allows a weakly attractive dispersion force to be induced between them. The present study provides an improved understanding of the role of the base sequence in deoxyribonucleic acid (DNA) or ribonucleic acid (RNA) in their interactions with carbon nanotubes of varying diameters.

  • 157.
    Grechnev, Alexei
    et al.
    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.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Balanced crystal orbital overlap population: a tool for analysing chemical bonds in solids2003In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 15, no 45, p. 7751-7761Article in journal (Refereed)
    Abstract [en]

    A new tool for analysing theoretically the chemical bonding in solids is proposed. A balanced crystal orbital overlap population (BCOOP) is an energy resolved quantity which is positive for bonding states and negative for antibonding states, hence enabling a distinction between bonding and antibonding contributions to the chemical bond. Unlike the conventional crystal orbital overlap population (COOP), BCOOP handles correctly the situation of crystal orbitals being nearly linear dependent, which is often the case in the solid state. Also, BCOOP is much less basis set dependent than COOP. A BCOOP implementation within the full-potential linear muffin tin orbital method is presented and illustrated for Si, TiC and Ru. Thus, BCOOP is compared to the COOP and crystal orbital Hamilton population (COHP) for systems with chemical bonds ranging from metallic to covalent character.

  • 158.
    Grechnev, Alexei
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Andersson, Per H.
    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.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Vennström, Marie
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Andersson, Yvonne
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    H-H interaction and structural phase transition in Ti3SnHx2002In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 66, no 23, p. 235104-Article in journal (Refereed)
  • 159.
    Grechnev, Alexei
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    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.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Wilhelmsson, Ola
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Layered compound Nb3SiC2 predicted from first-principles theory2004In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 85, no 15, p. 3071-3073Article in journal (Refereed)
    Abstract [en]

    A previously unobserved ternary carbide, Nb3SiC2, belonging to the family of the so-called Mn+1AXn or MAX phases is predicted from first-principles calculations. It has a theoretical bulk modulus of 296 Gpa, wich is much higher than that of Ti3SiC2. The new phase is metastable with a formation energy of +0.02 eV/atom. We suggest that the phase may possibly be synthesized using thin film technology. The chemical binding of Nb3SiC2 is investigated using the balanced crystal orbital overlap population indicator and it is found to be dominated by the formation of Nb4D-C 2p covalent bonds.

  • 160. Grechnev, G. E.
    et al.
    Ahuja, Rajeev
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics and Materials Science, Theoretical Magnetism.
    Eriksson, Olle
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics and Materials Science, Theoretical Magnetism.
    Magnetic susceptibility of hcp iron and the seismic anisotropy of Earth's inner core2003In: PHYSICAL REVIEW B, ISSN 1098-0121, Vol. 68, no 6, p. 064414-Article in journal (Refereed)
    Abstract [en]

    The seismic anisotropy of the Earth's core is believed to be due to a preferred orientation of hexagonal close packed (hcp) iron crystals that constitute the dominating element in the inner core. In this connection, the magnetic properties of the hcp iron in an external magnetic field are very interesting and are studied here by employing an ab initio full-potential linear muffin tin orbital method. By this means the magnetic susceptibility chi of hcp iron and its anisotropy energy for pressures and temperatures corresponding to the Earth's inner core conditions have been evaluated in the framework of the local spin density approximation. The accuracy of this method has been validated by calculating the anisotropic susceptibility of paramagnetic transition metals that form in the hcp crystal structure at ambient conditions. Our calculations demonstrate that for hcp iron the anisotropy of chi is dependent on the c/a ratio. In conjunction with recent data on the c/a ratio and elastic constants of hcp iron, the magnetic anisotropy can explain the seismic anisotropy of the Earth's inner core.

  • 161.
    Grigoriev, Anton
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Skorodumova, Natalia V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Simak, S. I.
    Wendin, G.
    Johansson, Börje
    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.
    Electron transport in stretched monoatomic gold wires2006In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 97, no 23, p. 236807-Article in journal (Refereed)
    Abstract [en]

    The conductance of monoatomic gold wires containing 3-7 gold atoms has been obtained from ab initio calculations. The transmission is found to vary significantly depending on the wire stretching and the number of incorporated atoms. Such oscillations are determined by the electronic structure of the one-dimensional (1D) part of the wire between the contacts. Our results indicate that the conductivity of 1D wires can be suppressed without breaking the contact.

  • 162.
    Guo, J H
    et al.
    Fysik II.
    Vayssieres, L
    Persson, C
    Ahuja, R
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics II. Physics IV. Fysik IV.
    Johansson, B
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics II. Physics IV. Fysik IV.
    Nordgren, J
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics II. Physics IV. Fysik II.
    Polarization-dependent soft-x-ray absorption of highly oriented ZnO microrod arrays2002In: Journal of Physics-Condensed Matter, Vol. 14, no 28, p. 6969-6974Article in journal (Refereed)
  • 163.
    Guo, J-H
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Gupta, Amita
    Sharma, Parmanand
    Rao, K. V.
    Marcus, M. A.
    Dong, C. L.
    Guillen, J. M. Osorio
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Butorin, Sergei
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Mattesini, Maurizio
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Glans, P. A.
    Smith, K. E.
    Chang, C. L.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    X-ray spectroscopic study of the charge state and local ordering of room-temperature ferromagnetic Mn-doped ZnO2007In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 19, no 17, p. 172202-Article in journal (Refereed)
    Abstract [en]

    The charge state and local ordering of Mn doped into a pulsed laser deposited single-phase thin film of ZnO are investigated by using x-ray absorption spectroscopy at the O K-edge, Mn K-edge and L-edge, and x-ray emission spectroscopy at the O K-edge and Mn L-edge. This film is ferromagnetic at room temperature. EXAFS measurement shows that Mn2+ replaces the Zn site in tetrahedral symmetry, and there is no evidence for either metallic Mn or MnO in the film. Upon Mn doping, the top of O 2p valence band extends into the bandgap, indicating additional charge carriers being created.

  • 164. Guo, Jinghua
    et al.
    Vayssieres, L
    Persson, C
    Ahuja, Rajeev
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics IV. Physics II.
    Johansson, Börje
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics IV. Physics II.
    Nordgren, Joseph
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics IV. Physics II.
    Polarization-dependent soft-x-ray absorption of a highly oriented ZnO microrod-array2005In: Journal of Physics-Condensed Matter, ISSN 1361-648X, Vol. 17, no 1, p. 235-240Article in journal (Refereed)
    Abstract [en]

    We report the soft-X-ray absorption and emission studies of NaCl, MgCl2, and AlCl3 in water solutions. The influences of cations on the water molecular structure can be seen as the absorption threshold edge shifted to high energy in the X-ray absorption spectra; the mixing of molecular orbital in 3a1 symmetry is reinforced as the intensity of 3a1 is further reduced; and the 1b1-emission peak shows the broadening and shift differently for Na+, Mg2+, and Al3+ water solutions, which indicates that the charge difference of the cations may not be the only playing role being responsible to the interactions between the cations and water molecules.

  • 165. Guo, Zhonglu
    et al.
    Sa, Baisheng
    Pathak, Biswarup
    Zhou, Jian
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Sun, Zhimei
    Band gap engineering in huge-gap semiconductor SrZrO3 for visible-light photocatalysis2014In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 39, no 5, p. 2042-2048Article in journal (Refereed)
    Abstract [en]

    Using SrZrO3 (SZO, the intrinsic band gap being 5.6 eV) as an example, we have investigated the design principles for huge-gap semiconductors with band gap larger than 5 eV for the application of efficient visible-light driven photocatalysts for splitting water into hydrogen. Based on the hybrid density function calculations, the electronic structures of mono-doped and co-doped SZO are investigated to obtain design principles for improving their photocatalytic activity in hydrogen generation. The cationic-anionic co-doping in SZO could reduce the band gap significantly and its electronic band position is excellent for the visible-light photocatalysis. This work reports a new type of candidate material for visible-light driven photocatalysis, i.e., huge-gap semiconductors with band gap larger than 5 eV. Furthermore, based on the present results we have proposed the design principles for band gap engineering that provides general guideline for other huge-gap semiconductors.

  • 166. Gupta, A
    et al.
    Ahuja, Rajeev
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics.
    High Temperature Ferromagnetism in Gallium Phosphide Doped with copper2006In: Phys. Rev. B, Vol. 74, p. 224449-Article in journal (Refereed)
  • 167. Gupta, Amita
    et al.
    Owens, Frank J.
    Rao, K. V.
    Iqbal, Zafar
    Guille, J. M. Osorio
    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.
    High-temperature ferromagnetism in Cu-doped GaP by SQUID magnetometry and ferromagnetic resonance measurements2006In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 74, no 22, p. 224449-Article in journal (Refereed)
    Abstract [en]

    The search for ferromagnetism above room temperature in semiconductors doped with paramagnetic ions has intensified in recent years because of the potential of combining magnetic information storage and electronic switching in one spintronic device. Here we report an observation of ferromagnetism well above room temperature in gallium phosphide doped with Cu2+ detected by ferromagnetic resonance and SQUID magnetometry. Other important features of the results in this p-type Cu-doped GaP are the high Curie temperature above 700 K significantly higher than previous observations, the relatively simple low-temperature bulk sintering process used to synthesize the material, which will significantly reduce the cost of large-scale production, and the use of copper as the dopant rather than manganese, which precludes ferromagnetic clusters or magnetic alloy impurities as the origin of the ferromagnetism. Ab initio calculations also show the existence of ferromagnetism in Cu-doped GaP. When the spin-orbit coupling is included, the total moment is enhanced and we get a total magnetic moment of 0.31 mu(B) with a local moment on Cu 0.082 and on P 0.204 mu(B).

  • 168. He, Haiying
    et al.
    Scheicher, Ralph H.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics IV.
    Pandey, Ravindra
    Rocha, Alexandre Reily
    Sanvito, Stefano
    Grigoriev, Anton
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics IV.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics IV.
    Karna, Shashi P.
    Functionalized Nanopore-Embedded Electrodes for Rapid DNA Sequencing2008In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 112, no 10, p. 3456-3459Article in journal (Refereed)
    Abstract [en]

    With the aim of improving nanopore-based DNA sequencing, we explored the effects of functionalizing the embedded gold electrodes with purine and pyrimidine molecules. Hydrogen bonds formed between the molecular probe and target bases stabilize the scanned DNA unit against thermal fluctuations and thus greatly reduce noise in the current signal. The results of our first-principles study indicate that this proposed scheme could allow DNA sequencing with a robust and reliable yield, producing current signals that differ by at least 1 order of magnitude for the different bases.

  • 169. He, Yuhui
    et al.
    Scheicher, Ralph
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Grigoriev, Anton
    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.
    Long, Shibing
    Huo, Zongliang
    Liu, Ming
    DNA sequencing with nanopore-embedded bilayer-graphene nanoelectrodes2010In: ICSICT-2010 - 2010 10th IEEE International Conference on Solid-State and Integrated Circuit Technology, Proceedings, p. 1483-1485Article in journal (Refereed)
  • 170. He, Yuhui
    et al.
    Scheicher, Ralph
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Grigoriev, Anton
    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.
    Long, Shibing
    Ji, Zhuoyu
    Yu, Zhaoan
    Liu, Ming
    Fast DNA sequencing via transverse differential conductance2010Conference paper (Refereed)
    Abstract [en]

    We propose using characteristic transverse differential conductance for solid-state nanopore-based DNA sequencing and have explored this idea by performing molecular dynamics simulations on the translocation progress of single-stranded DNA molecule through the nanopore, and calculating the associated transverse differential conductance. Our results show that measurement of the transverse differential conductance is suitable to successfully discriminate between the four nucleotide types, and we show that this identification could even withstand electrical noise caused by fluctuations due to changes in the DNA orientation. Our findings demonstrate several compelling advantages of the differential conductance approach, which may lead to important applications in rapid genome sequencing.

  • 171.
    He, Yuhui
    et al.
    Laboratory of Nano-Fabrication and Novel Devices Integrated Technology, Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029, China.
    Scheicher, Ralph H.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Grigoriev, Anton
    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.
    Long, Shibing
    Laboratory of Nano-Fabrication and Novel Devices Integrated, Technology, Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029, China.
    Huo, ZongLiang
    Laboratory of Nano-Fabrication and Novel Devices Integrated, Technology, Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029, China.
    Liu, Ming
    Laboratory of Nano-Fabrication and Novel Devices Integrated Technology, Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029, China.
    Enhanced DNA Sequencing Performance Through Edge-Hydrogenation of Graphene Electrodes2011In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 21, no 14, p. 2674-2679Article in journal (Refereed)
    Abstract [en]

    The use of graphene electrodes with hydrogenated edges for solid-state nanopore-based DNA sequencing is proposed, and molecular dynamics simulations in conjunction with electronic transport calculations are performed to explore the potential merits of this idea. The results of the investigation show that, compared to the unhydrogenated system, edge-hydrogenated graphene electrodes facilitate the temporary formation of H-bonds with suitable atomic sites in the translocating DNA molecule. As a consequence, the average conductivity is drastically raised by about 3 orders of magnitude while exhibiting significantly reduced statistical variance. Furthermore, the effect of the distance between opposing electrodes is investigated and two regimes identified: for narrow electrode separation, the mere hindrance due to the presence of protruding hydrogen atoms in the nanopore is deemed more important, while for wider electrode separation, the formation of H-bonds becomes the dominant effect. Based on these findings, it is concluded that hydrogenation of graphene electrode edges represents a promising approach to reduce the translocation speed of DNA through the nanopore and substantially improve the accuracy of the measurement process for whole-genome sequencing.

  • 172. He, Yuhui
    et al.
    Shao, Lubing
    Scheicher, Ralph
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Grigoriev, Anton
    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.
    Long, Shibing
    Ji, Zhuoyu
    Yu, Zhaoan
    Liu, Ming
    Differential conductance as a promising approach for rapid DNA sequencing with nanopore-embedded electrodes2010In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 97, no 4, p. 043701-Article in journal (Refereed)
    Abstract [en]

    We propose an approach for nanopore-based DNA sequencing using characteristic transverse differential conductance. Molecular dynamics and electron transport simulations show that thetransverse differential conductance during the translocation of DNA through the nanopore isdistinguishable enough for the detection of the base sequence and can withstand electrical noisecaused by DNA structure fluctuation. Our findings demonstrate several advantages of the transverseconductance approach, which may lead to important applications in rapid genome sequencing.

  • 173. Heathman, S.
    et al.
    Haire, R. G.
    Le Bihan, T.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Li, S.
    Luo, Wei
    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.
    The unique high-pressure behavior of curiurn probed further using alloys2007In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 444, p. 138-141Article in journal (Refereed)
    Abstract [en]

    The changing role of the 5f electrons across the actinide series has been of prime interest for many years. The remarkable behavior of americium's 5f electrons under pressure was determined experimentally a few years ago and it precipitated a strong interest in the heavy element community. Theoretical treatments of americium's behavior under pressure followed and continue today. Experimental and theoretical findings regarding curium's behavior under pressure have shown that the pressure behavior of curium was not a mirror image of that for americium. Rather, one of the five crystallographic phases observed with curium (versus four for americium) was a unique monoclinic structure whose existence is due to a spin stabilization effect by curium's 5f(7) electronic configuration and its half-filled 5f-shell. We review briefly the behavior of pure curium under pressure but focus on the pressure behaviors of three curium alloys with the intent of comparing them with pure curium. An important experimental finding confirmed by theoretical computations, is that dilution of curium with its near neighbors is sufficient to prevent the formation of the unique C2/c phase that appears in pure Cm metal under pressure. As this unique C2/c phase is very sensitive to having a 5f7 configuration to maximize the magnetic spin polarization, dilution of this state with adjacent actinide neighbors reduces its stability.

  • 174. Heathman, S. K.
    et al.
    Ahuja, Rajeev
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics IV.
    Johansson, Börje
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics IV.
    A High-Pressure Structure in Curium Linked to Magnetism2005In: Science, Vol. 309, p. 110-Article in journal (Refereed)
  • 175. Heathman, S.
    et al.
    Le Bihan, T.
    Yagoubi, S.
    Johansson, Börje
    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.
    Structural investigation of californium under pressure2013In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 87, no 21, p. 214111-Article in journal (Refereed)
    Abstract [en]

    The high-pressure structural behavior of californium has been studied experimentally and theoretically up to 100 GPa. A valence change from divalent to trivalent forms was observed under modest pressure revealing californium to be the only actinide to exhibit more than one metallic valence at near to ambient conditions as is the case for cerium in the lanthanide series. Three metallic valencies and four different crystallographic phases were observed in californium as a function of pressure. High-pressure techniques, synchrotron radiation, and ab initio electronic structure calculations of total energies were used to investigate the material and to determine the role which californium's 5f electrons play in influencing these transitions. The crystallographic structures observed are similar to those found in the preceding actinide elements, curium and americium, with the initially localized 5f states becoming completely delocalized under the influence of high pressure.

  • 176.
    Heciri, D.
    et al.
    Univ Badji Mokhtar, Fac Sci, Dept Phys, Lab Studies Surface & Interfaces Solid Matter LES, Annaba, Algeria.
    Belkhir, H.
    Univ Badji Mokhtar, Fac Sci, Dept Phys, Lab Studies Surface & Interfaces Solid Matter LES, Annaba, Algeria.
    Hamidani, A.
    Univ 8 Mai Guelma, Fac Math Comp & Mat Sci, Phys Lab Guelma, Guelma 24000, Algeria.
    Bououdina, M.
    Univ Bahrain, Coll Sci, Dept Phys, POB 32038, Zallaq, Bahrain.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Theoretical investigation of structural, electronic and optical properties of (BeS)(1) /(BeSe)(1), (BeSe)(1)/(BeTe)(1) and (BeS)(1)/(BeTe)(1) superlattices under pressure2018In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 713, p. 71-84Article in journal (Refereed)
    Abstract [en]

    The influence of hydrostatic pressure on structural, electronic and optical properties of short period (BeS)(1)/(BeSe)(1), (BeSe)(1)/(BeTe)(1) and (BeS)(1)/(BeTe)1 superlattices, has been investigated. The lattice parameters a and c for the tetragonal unit cell obtained by total energy calculations are in good agreement with the values calculated by macroscopic elasticity theory. The (BeS)(1)/(BeSe)(1) superlattice possesses an indirect band gap while (BeSe)(1)/(BeTe)(1) and (BeS)(1)/(BeTe)(1) superlattices possess a direct band gap. The pressure ranges from 0 to 47 GPa for (BeS)(1)/(BeSe)(1), 0 to 39 GPa for (BeSe)(1)/(BeTe)(1), and 0 to 45 GPa for (BeS)(1)/(BeTe)(1) , meanwhile the pressure dependence of the energy band gap along different symmetry directions obey the equation E-g(p)= E-g+ ap + bp(2). The pressure coefficient of the indirect band gap for (BeS)(1)/(BeSe)(1) is - 22.5675 x 10(-3) eV(GPa)(-1), while that of the direct band gap is estimated as - 25.8581 x 10(-3)eV(GPa)(-1) and - 24.4695 x 10(-3)eV(GPa)(-1) for (BeSe)(1)/(BeTe)(1) and (BeS)(1)/(BeTe)(1), respectively. The variation of the static dielectric constant with pressure is discussed.

  • 177.
    Hjorvarsson, B
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics.
    Guo, JH
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics.
    Ahuja, R
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics.
    Ward, RCC
    Andersson, G
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics.
    Eriksson, O
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics.
    Wells, MR
    Sathe, C
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics.
    Agui, A
    Butorin, SM
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics.
    Nordgren, J
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics.
    Probing the local electronic structure in the H induced metal-insulator transition of Y1999In: JOURNAL OF PHYSICS-CONDENSED MATTER, Vol. 11, p. L119-Article in journal (Refereed)
    Abstract [en]

    The occupied acid unoccupied valence band states of yttrium (Y) metal, Y dihydride and Y trihydride were measured by soft x-ray emission and absorption spectroscopy. The experiments were complemented by first principles calculations. Both experiments and

  • 178.
    Houmad, M.
    et al.
    Mohammed V Univ, Fac Sci, Lab Magnetism & Phys High Energies, Phys Dept, BP 1014, Rabat, 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, Lab Phys Mat & Modelisat Syst LP2MS, Unite Associee CNRST URAC 08, Fac Sci,Phys Dept, BP 11201, Meknes, Morocco.
    Ainane, Abdelmajid
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics. Univ Moulay Ismail, Lab Phys Mat & Modelisat Syst LP2MS, Unite Associee CNRST URAC 08, Fac Sci,Phys Dept, BP 11201, Meknes, Morocco;Max Planck Inst Phys Complexer Syst, Nothnitzer Str 38, D-01187 Dresden, Germany.
    El Kenz, A.
    Mohammed V Univ, Fac Sci, Lab Magnetism & Phys High Energies, Phys Dept, BP 1014, Rabat, Morocco.
    Benyoussef, A.
    Mohammed V Univ, Fac Sci, Lab Magnetism & Phys High Energies, Phys Dept, BP 1014, Rabat, Morocco.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Improving the electrical conductivity of Siligraphene SiC7 by strain2019In: Optik (Stuttgart), ISSN 0030-4026, E-ISSN 1618-1336, Vol. 177, p. 118-122Article in journal (Refereed)
    Abstract [en]

    Using the 1st principle calculations founded on Density Functional Theory (DFT), we examined the strain effect of band gap (BG) and electrical property (EP) of Siligraphene (g-SiC7) under biaxial strains (Compressive and tensile) using Generalized Gradient Approximation (GGA). We found that the BG of g-SiC7 was decreasing as function of the strain and we remarked that the electrical conductivity of g-SiC7 under biaxial strains become important of 6% for tension effect. For the compressive, we obtained an increase for all compressive applying, but we remarked the higher and lower values are successively -2% and -6%. Last not least, we deduced that it's possible to increase the electrical conductivity of g-SiC7. Also, this material can be used in solar cell applications and for photo-voltaic (PV) applications as a light donor material.

  • 179.
    Htoutou, K.
    et al.
    Univ Moulay Ismail, Lab Phys Mat & Modelisat Syst LP2MS, Unit Associee CNRST URAC 08, Phys Dept,Fac Sci, BP 11201, Meknes, Morocco.;CRMEF, BP 255, Meknes, Morocco..
    Oubelkacem, A.
    Univ Moulay Ismail, Lab Phys Mat & Modelisat Syst LP2MS, Unit Associee CNRST URAC 08, Phys Dept,Fac Sci, BP 11201, Meknes, Morocco..
    Benhouria, Y.
    Univ Moulay Ismail, Lab Phys Mat & Modelisat Syst LP2MS, Unit Associee CNRST URAC 08, Phys Dept,Fac Sci, BP 11201, Meknes, Morocco..
    Essaoudi, I.
    Univ Moulay Ismail, Lab Phys Mat & Modelisat Syst LP2MS, Unit Associee CNRST URAC 08, Phys Dept,Fac Sci, BP 11201, Meknes, Morocco..
    Ainane, Abdelmajid
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics. Univ Moulay Ismail, Lab Phys Mat & Modelisat Syst LP2MS, Unit Associee CNRST URAC 08, Phys Dept,Fac Sci, BP 11201, Meknes, Morocco..
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    The Magnetic Properties of the Mixed Ferrimagnetic Ising System with Random Crystal Field2017In: Journal of Superconductivity and Novel Magnetism, ISSN 1557-1939, E-ISSN 1557-1947, Vol. 30, no 5, p. 1247-1256Article in journal (Refereed)
    Abstract [en]

    Using the effective-field theory EFT based on the probability distribution technique, the effect of the random crystal field on the magnetic properties of ferrimagnetic mixed Ising system with both spin-1 and spin-3/2 is investigated. The critical temperature is discussed as function of different strengths of the random crystal field and the exchange interactions. The phase diagrams are calculated numerically for a square lattice and the number of characteristic phenomena, such as the tricritical point are found. Our results are different to that reported in Souza et al. (Physica A 444, 589-600 2016).

  • 180.
    Hu, Shuanglin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Li, Shuyi
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Granqvist, Claes-Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Hermansson, Kersti
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Niklasson, Gunnar A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Scheicher, Ralph H.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Optical properties of Mg-doped VO2: Absorption measurements and hybrid functional calculations2012In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 101, no 20, p. 201902-Article in journal (Refereed)
    Abstract [en]

    Mg-doped VO2 thin films with thermochromic properties were made by reactive DC magnetron co-sputtering onto heated substrates, and spectral absorption was recorded at room temperature in the 0.5 < <(h)over bar>omega < 3.5 eV energy range. Clear evidence was found for a widening of the main band gap from 1.67 to 2.32 eV as the Mg/(V + Mg) atomic ratio went from zero to 0.19, thereby significantly lowering the luminous absorption. This technologically important effect could be reconciled with spin-polarized density functional theory calculations using the Heyd-Scuseria-Ernzerhof [Heyd et al., J. Chem. Phys. 118, 8207 (2003); ibid. 124, 219906 (2006)] hybrid functional. Specifically, the calculated luminous absorptance decreased when the Mg/(V + Mg) ratio was increased from 0.125 to 0.250.

  • 181.
    Huang, L. M.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Silvearv, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Araújo, C. Moysés
    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.
    Defect-induced strong ferromagnetism in Cr-doped In2O3 from first-principles theory2010In: Solid State Communications, ISSN 0038-1098, E-ISSN 1879-2766, Vol. 150, no 13-14, p. 663-665Article in journal (Refereed)
    Abstract [en]

    We demonstrate by means of first-principles calculations that the high Curie temperature observed in Cr-doped In2O3 is mediated by intrinsic p-type defects, namely In vacancies or O interstitials. Charge transfer from Cr 3d states to the hole states formed by these defects makes Cr ions in the mixed valence state, giving rise to a strong ferromagnetic coupling. Calculated formation energies of various defects also show that doping Cr in In2O3 could greatly lower the formation energies of p-type intrinsic defects even in oxygen-deficient growth conditions. These results advance our understanding of the underlying physics of diluted magnetic oxides. (C) 2009 Elsevier Ltd. All rights reserved.

  • 182.
    Huang, L. M.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Vitos, Levente
    Kwon, S. K.
    Johansson, Börje
    Ahuja, Rajeev
    Thermaelastic properties of ramdom alloys from first-principles theory2006In: Phys. Rev. B, Vol. 73, p. 104203-Article in journal (Refereed)
  • 183.
    Huang, L. M.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Århammar, Cecilia
    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.
    Silvearv, Fredrik
    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.
    Tuning magnetic properties of In2O3 by control of intrinsic defects2010In: Europhysics letters, ISSN 0295-5075, E-ISSN 1286-4854, Vol. 89, no 4, p. 47005-Article in journal (Refereed)
    Abstract [en]

    The electronic structure and magnetic properties of In2O3 with four kinds of intrinsic point defects (O vacancy, In interstitial, O interstitial, and In vacancy) have been theoretically studied using the density functional theory. The defect energy states of the O vacancy and In interstitial are close to the bottom of conduction band and act as shallow donors, while the defect energy states of the In vacancy and O interstitial are just above the top of the valence band and act as shallow acceptors. Without addition of any magnetic ions, all the hole states are completely spin polarized, while the electron states display no spin polarization. This implies that semiconducting In2O3 can display magnetic ordering, purely due to the intrinsic defects. However, the formation energies for neutral p-type defects are too high to be thermodynamically stable at reasonable temperatures. Nevertheless, it is shown that negative charging can greatly decrease the formation energies of p-type defects, simultaneously removing the local magnetic moments. We conlcude that V-In''' and O-I '' will be the dominant compensating defects as In2O3 is doped with TM ions, such as Sn, Mo, V and Cr. This result is consistent with the general view that the p-type defect is a key feature to mediate ferromagnetic coupling between transition metal ions of dilute concentration in metal oxides. Copyright (C) EPLA, 2010

  • 184.
    Huang, L
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics.
    Rosa, A
    Ahuja, Rajeev
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics.
    Ferromagentism in (Zn,Cu)O from first principles theory2006In: Phys. Rev. B, Vol. 74, p. 075206-Article in journal (Refereed)
  • 185.
    Huang, L
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Vitos, Levente
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Kwon, S K
    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.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Thermo-elastic properties of random alloys from first-principles theory2006In: Phys. Rev. B, Vol. 73, p. 104203-Article in journal (Refereed)
  • 186.
    Huang, Lunmei
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Ramzan, Muhammad
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Vitos, Levente
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Johansson, Börje
    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.
    Anomalous temperature dependence of elastic constant c44 in V, Nb, Ta, Pd, and Pt2010In: Journal of Physics and Chemistry of Solids, ISSN 0022-3697, E-ISSN 1879-2553, Vol. 71, no 8, p. 1065-1068Article in journal (Refereed)
    Abstract [en]

    The electrochemical reduction processes on stainless-steel substrates from an aqueous electrolyte composed of nitric acid, Bi3+, HTeO2+, SbO+ and H2SeO3 systems were investigated using cyclic voltammetry. The thin films with a stoichiometry of Bi2Te3, Bi0.5Sb1.5Te3 and Bi2Te2.7Se0.3 have been prepared by electrochemical deposition at selected potentials. The structure, composition, and morphology of the films were studied by X-ray diffraction (XRD), environmental scanning electron microscopy (ESEM) and electron microprobe analysis (EMPA). The results showed that the films were single phase with the rhombohedral Bi2Te3 structure. The morphology and growth orientation of the films were dependent on the deposition potentials.

  • 187.
    Huang, Lunmei
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Rosa, A.L.
    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.
    Ferromagnetism in Cu-doped ZnO from first-principles theory2006In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 74, no 7, p. 075206-Article in journal (Refereed)
    Abstract [en]

    Using the first-principles method based on the density functional theory, we have studied the electronic structure and the ferromagnetic stability in Cu-doped ZnO. The system shows the half-metallic ground state and the high ferromagnetic stability for all the calculated Cu concentrations within the generalized gradient approximation (GGA). The delocalized holes induced by O 2p and Cu 3d hybridization are found to be very efficient to mediate the ferromagnetic exchange interaction. While going beyond the GGA, the ferromagnetic stability as a function of the Coulomb correlation U shows a sudden decrease when U=3 eV where the system becomes an insulating ground state. By doping the p-type or n-type defects, the holes can be increased or compensated. The n-type defect, such as O vacancy, Zn interstitial, or H interstitial decreases the ferromagnetic stability, while the p-type defect, such as Zn vacancy, increases the ferromagnetic stability. By keeping the system to be the metallic ground state, the defect of the Zn vacancy could retain the high ferromagnetic stability of the system even in the case of U.

  • 188.
    Huang, Lunmei
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics IV.
    Skorodumova, Natalia
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics IV.
    Belonoshko, Anatoly
    Johansson, Börje
    Ahuja, Rajeev
    Carbon in iron phases under high pressure2005In: Geophysical Research Letters, Vol. 32Article in journal (Refereed)
    Abstract [en]

    The influence of carbon impurities on the properties of iron phases (bcc, hcp, dhcp, fcc) has been studied using the first-principles projector augmented-wave (PAW) method for a wide pressure range. It is shown that the presence of ~6 at. % of interstitial carbon has a little effect on the calculated structural sequence of the iron phases under high pressure. The bcc → hcp transition both for pure iron and iron containing carbon takes place around 9 GPa. According to the enthalpies comparison, the solubility of carbon into the iron solid is decreased by high pressure. The coexistence of iron carbide (Fe3C) + pure hcp Fe is most stable phase at high pressure compared with other phases. Based on the analysis of the pressure-density dependences for Fe3C and hcp Fe, we suggest that there might be some fraction of iron carbide present in the core.

  • 189.
    Hussain, T.
    et al.
    Univ Western Australia, Sch Mol Sci, Perth, WA 6009, Australia.
    Singh, Deobrat
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. SV Natl Inst Technol, Dept Appl Phys, Adv Mat Lab, Surat 395007, Gujarat, India.
    Gupta, Sanjeev K.
    St Xaviers Coll, Dept Phys, Computat Mat & Nanosci Grp, Ahmadabad 380009, Gujarat, India.
    Karton, A.
    Univ Western Australia, Sch Mol Sci, Perth, WA 6009, Australia.
    Sonvane, Yogesh
    SV Natl Inst Technol, Dept Appl Phys, Adv Mat Lab, Surat 395007, Gujarat, India.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Royal Inst Technol KTH, Dept Mat & Engn, Appl Mat Phys, S-10044 Stockholm, Sweden.
    Efficient and selective sensing of nitrogen-containing gases by Si2BN nanosheets under pristine and pre-oxidized conditions2019In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 469, p. 775-780Article in journal (Refereed)
    Abstract [en]

    Motivated by the promise of two-dimensional nanostructures in the field of gas sensing, we have employed van der Waals corrected density functional theory calculations to study the structural, electronic and gas sensing propensities of the recently designed Si2BN monolayer. Our rigorous simulations reveal that the representative members of nitrogen-containing gases (NCGs) such as NO, NO2 and NH3 binds extremely strongly on pristine Si2BN monolayer. However, a strong dissociative adsorption in case of NO and NO2 would poison the Si2BN and ultimately reversibility of the monolayer would be compromised. Exploring the sensing mechanism in more realistic pre-oxidized conditions, the binding characteristics of O2@Si2BN changed dramatically, resulting into much lower adsorption in associative manner for all NO, NO2 and NH3. A visible change in work function indicates the variation in conductivity of O2@Si2BN upon the exposure of incident gases. Sustainable values of binding energies would also ensure a quick recovery time that makes O2@Si2BN an efficient nano sensor for pollutants like NCGs.

  • 190.
    Hussain, T.
    et al.
    Univ Western Australia, Sch Mol Sci, Perth, WA 6009, Australia;Univ Queensland, Ctr Theoret & Computat Mol Sci, Australian Inst Bioengn & Nanotechnol, Brisbane, Qld 4072, Australia.
    Vovusha, H.
    KAUST, Phys Sci & Engn Div PSE, Thuwal 239556900, Saudi Arabia.
    Kaewmaraya, T.
    Khon Kaen Univ, Integrated Nanotechnol Res Ctr, Dept Phys, Khon Kaen, Thailand.
    Karton, A.
    Univ Western Australia, Sch Mol Sci, Perth, WA 6009, Australia.
    Amornkitbamrung, V
    Khon Kaen Univ, Integrated Nanotechnol Res Ctr, Dept Phys, Khon Kaen, Thailand.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Graphitic carbon nitride nano sheets functionalized with selected transition metal dopants: an efficient way to store CO22018In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 29, no 41, article id 415502Article in journal (Refereed)
    Abstract [en]

    Proficient capture of carbon dioxide (CO2) is considered to be a backbone for environment protection through countering the climate change caused by mounting carbon content. Here we present a comprehensive mechanism to design novel functional nanostructures capable of capturing a large amount of CO2 efficiently. By means of van der Waals corrected density functional theory calculations, we have studied the structural, electronic and CO2 storage properties of carbon nitride (g-C6N8) nano sheets functionalized with a range of transition metal (TM) dopants ranging from Sc to Zn. The considered TMs bind strongly to the nano sheets with binding energies exceeding their respective cohesive energies, thus abolishing the possibility of metal cluster formation. Uniformly dispersed TMs change the electronic properties of semiconducting g-C6N8 through the transfer of valence charges from the former to the latter. This leaves all the TM dopants with significant positive charges, which are beneficial for CO2 adsorption. We have found that each TM's dopants anchor a maximum of four CO2 molecules with suitable adsorption energies (-0.15 to -1.0 eV) for ambient condition applications. Thus g-C6N8 nano sheets functionalized with selected TMs could serve as an ideal sorbent for CO2 capture.

  • 191.
    Hussain, T.
    et al.
    Univ Western Australia, Sch Mol Sci, Perth, WA 6009, Australia;Univ Queensland, Australian Inst Bioengn & Nanotechnol, Ctr Theoret & Computat Mol Sci, Brisbane, Qld 4072, Australia.
    Vovusha, Hakkim
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. KAUST, Phys Sci & Engn Div PSE, Thuwal 239556900, Saudi Arabia.
    Umer, R.
    Univ Southern Queensland, Ctr Future Mat, Toowoomba, Qld 4350, 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.
    Superior sensing affinities of acetone towards vacancy induced and metallized ZnO monolayers2018In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 456, p. 711-716Article in journal (Refereed)
    Abstract [en]

    The sensing propensities of acetone molecule towards zinc oxide monolayers (ZnO-ML) have been studied by means of density functional theory (DFT) calculations. Our van der Waals induced first principles calculations revealed that pristine ZnO-ML barely binds acetone, which limits its application as acetone sensing materials. However the formation of vacancies and foreign element doping improves acetone binding drastically. Among several defects, divacancy, and metal doping Li, Sc and Ti functionalization on ZnO-ML has been found the most promising ones. Presence of dangling electrons and partial positive charges in case of vacancy-induced and metallized ZnO-ML respectively, is believed to enhance the binding of acetone on the monolayers. The acetone-ZnO binding behavior has been further explained through studying the electronic properties by density of states and charge transfer mechanism though Bader analysis. Thus defected and metallized ZnO-ML could be a promising nano sensor for efficient sensing/capture of acetone.

  • 192.
    Hussain, Tanveer
    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. Department of Materials and Engineering, Royal Institute of Technology (KTH).
    Metal Functionalized Silicene for Efficient Hydrogen Storage2013In: ChemPhysChem, ISSN 1439-4235, E-ISSN 1439-7641, Vol. 14, no 15, p. 3463-3466Article in journal (Refereed)
    Abstract [en]

    First-principles calculations based on density functional theory are used to investigate the electronic structure along with the stability, bonding mechanism, band gap, and charge transfer of metal-functionalized silicene to envisage its hydrogen-storage capacity. Various metal atoms including Li, Na, K, Be, Mg, and Ca are doped into the most stable configuration of silicene. The corresponding binding energies and charge-transfer mechanisms are discussed from the perspective of hydrogen-storage compatibility. The Li and Na metal dopants are found to be ideally suitable, not only for strong metal-to-substrate binding and uniform distribution over the substrate, but also for the high-capacity storage of hydrogen. The stabilities of both Li- and Na-functionalized silicene are also confirmed through molecular dynamics simulations. It is found that both of the alkali metals, Li+ and Na+, can adsorb five hydrogen molecules, attaining reasonably high storage capacities of 7.75 and 6.9 wt%, respectively, with average adsorption energies within the range suitable for practical hydrogen-storage applications.

  • 193.
    Hussain, Tanveer
    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.
    De Sarkar, Abir
    Johansson, Börje
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Enhancement of energy storage capacity of Mg functionalized silicene and silicane under external strain2014In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 105, no 12, p. 123903-Article in journal (Refereed)
    Abstract [en]

    The electronic structure, stability, and hydrogen storage capacity of strain induced Mg functionalized silicene (SiMg) and silicane (SiHMg) monolayers have been studied by means of van der Waals induced first principles calculations. A drastic increase in the binding energy of Mg adatoms on both the monolayers under the biaxial symmetric strain of 10% ensures the uniform distribution of dopants over the substrates. A significant positive charge on each Mg accumulates a maximum of six H-2 molecules with H-2 storage capacity of 8.10% and 7.95% in case of SiMg and SiHMg, respectively. The average adsorption energy for H-2 molecules has been found ideal for practical H-2 storage materials.

  • 194.
    Hussain, Tanveer
    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.
    Kang, T. W.
    Johansson, Borje
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    BC3 Sheet Functionalized with Lithium-Rich Species Emerging as a Reversible Hydrogen Storage Material2015In: ChemPhysChem, ISSN 1439-4235, E-ISSN 1439-7641, Vol. 16, no 3, p. 634-639Article in journal (Refereed)
    Abstract [en]

    The decoration of a BC3 monolayer with the polylithiated molecules CLi4 and OLi2 has been extensively investigated to study the hydrogen-storage efficiency of the materials by first principles electronic structure calculations. The binding energies of both lithiated species with the BC3 substrate are much higher than their respective cohesive energies, which confirms the stability of the doped systems. A significant positive charge on the Li atom in each of the dopants facilitates the adsorption of multiple H-2 molecules under the influence of electrostatic and van der Waals interactions. We observe a high H-2-storage capacity of 11.88 and 8.70 wt% for the BC3-CLi4 and BC3-OLi2 systems, respectively, making them promising candidates as efficient energy-storage systems.

  • 195.
    Hussain, Tanveer
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    De Sarkar, Abir
    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.
    Strain induced lithium functionalized graphane as a high capacity hydrogen storage material2012In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 101, no 10, p. 103907-Article in journal (Refereed)
    Abstract [en]

    Strain effects on the stability, electronic structure, and hydrogen storage capacity of lithium-doped graphane have been investigated by state-of-the-art first principles density functional theory. Molecular dynamics simulations have confirmed the stability of Li on graphane sheet when it is subject to 10% of tensile strain. Under biaxial asymmetric strain, the binding energy of Li of graphane (CH) sheet increases by 52% with respect to its bulk's cohesive energy. With 25% doping concentration of Li on CH sheet, the gravimetric density of hydrogen storage is found to reach up to 12.12wt. %. The adsorption energies of H-2 are found to be within the range of practical H-2 storage applications. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4751249]

  • 196.
    Hussain, Tanveer
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    De Sarkar, Abir
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Maark, Tuhina Adit
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Sun, Weiwei
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Strain and doping effects on the energetics of hydrogen desorption from the MgH2 (001) surface2013In: Europhysics letters, ISSN 0295-5075, E-ISSN 1286-4854, Vol. 101, no 2, p. 27006-Article in journal (Refereed)
    Abstract [en]

    On the basis of first-principles calculations we have systematically investigated the energetics of hydrogen desorption from the MgH2 (001) surface. Based on total energy and electronic structure calculations, two modes namely strain and doping of selected dopants (Al, Si, Ti) and the combined effect of both on the dehydrogenation energies (Delta H) of MgH2 (001) systems have been analyzed. The maximum improvement in Delta H has been obtained with the combined effect of doping and strain. Among all the dopants, Al gives the lowest value of Delta H when the system Al-MgH2 is subjected to a 7.5% biaxial symmetric strain whereas the Si-MgH2 systems show the least improvement in Delta H. The doping of Ti on MgH2 (001) is also very beneficial even without strain. The reduction in Delta H is caused by the charge localization on the metal atoms, destabilization and the weakening of metal-hydrogen bonds.

  • 197.
    Hussain, Tanveer
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Islam, Muhammed Shafiqul
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Rao, G. S.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Panigrahi, Puspamitra
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Gupta, D.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Hydrogen storage properties of light metal adatoms (Li, Na) decorated fluorographene monolayer2015In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 26, no 27, article id 275401Article in journal (Refereed)
    Abstract [en]

    Owing to its high energy density, the potential of hydrogen (H-2) as an energy carrier has been immense, however its storage remains a big obstacle and calls for an efficient storage medium. By means of density functional theory (DFT) in spin polarized generalized gradient approximation (GGA), we have investigated the structural, electronic and hydrogen storage properties of a light alkali metal (Li, Na) functionalized fluorographene monolayer (FG). Metal adatoms bind to the FG with significantly high binding energy, much higher than their cohesive energies, which helps to achieve a uniform distribution of metal adatoms on the monolayer and consequently ensure reversibility. Due to a difference of electronegativities, each metal adatom transfers a substantial amount of its charge to the FG monolayer and attains a partial positive state, which facilitates the adsorption of multiple H-2 molecules around the adatoms by electrostatic as well as van der Waals interactions. To get a better description of H-2 adsorption energies with metal-doped systems, we have also performed calculations using van der Waals corrections. For both the functionalized systems, the results indicate a reasonably high H-2 storage capacity with H2 adsorption energies falling into the range for the practical applications.

  • 198.
    Hussain, Tanveer
    et al.
    Univ Queensland, Ctr Theoret & Computat Mol Sci, Australian Inst Bioengn & Nanotechnol, Brisbane, Qld 4072, Australia..
    Kaewmaraya, Thanayut
    Univ Paris 11, Inst Elect Fondamentale, UMR 8622, F-91405 Orsay, France.;Khon Kaen Univ, Fac Sci, Dept Phys, Khon Kaen 40002, Thailand..
    Chakraborty, Sudip
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics. Royal Inst Technol KTH, Appl Mat Phys, Dept Mat & Engn, S-10044 Stockholm, Sweden..
    Defect and Substitution-Induced Silicene Sensor to Probe Toxic Gases2016In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 120, no 44, p. 25256-25262Article in journal (Refereed)
    Abstract [en]

    Structural, electronic, and gas-sensing properties of pure, defected, and substituted silicene monolayer have been studied using first-principles calculations based on density functional theory. The spin-polarized calculations with van der Waals effect taken into consideration have revealed that the pristine silicene sheet rarely adsorbs the CO2, H2S, and SO2 gas molecules, which restricts the gas-sensing application of this 2D material. However, inducing vacancy defect in silicene drastically changes the electronic properties, and as a consequence it also improves the binding of exposed gas molecules significantly. Our Bader charge analysis reveals that a considerable amount of charge is being transferred from the defected silicene to the gases, resulting in binding energy improvement between silicene and the gas molecules. The change in binding energies has further been explained by plotting density of states. In addition to the vacancy defects, we have also considered the substitution of Al, B, N, and S in silicene. We found that the sensing propensity of silicene is more sensitive to the vacancy defect, as compared with the impurities.

  • 199.
    Hussain, Tanveer
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Kaewmaraya, Thanayut
    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. Department of Materials and Engineering, Royal Institute of Technology (KTH).
    Functionalization of hydrogenated silicene with alkali and alkaline earth metals for efficient hydrogen storage2013In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 15, no 43, p. 18900-18905Article in journal (Refereed)
    Abstract [en]

    First principles density functional theory has been employed to investigate the electronic structure along with the stability, bonding mechanism, band gap and charge transfer of metal functionalized hydrogenated silicene (SiH), or silicane, in order to envisage the hydrogen storage capacity. Various metal adatoms including Li, Na, K, Be, Mg and Ca have been doped on the most stable chair like configuration of silicane. The corresponding binding energies and charge transfer mechanism have been discussed from the perspective of H-2 storage ability. The Li and Na metal adatoms have been found to be ideally suitable not only for their strong metal to substrate binding and uniform distribution over the substrate but also for their high capacity for storage of hydrogen. The stability of both Li and Na functionalized SiH has also been confirmed by MD simulations. It was found that both Li+ and Na+ adsorbed four H-2 molecules attaining reasonably high storage capacities of 6.30 wt% and 5.40 wt% respectively with average adsorption energies lying within the range suitable for practical H-2 storage applications, in contrast with alkaline earth metals.

  • 200.
    Hussain, Tanveer
    et al.
    Univ Queensland, Australian Inst Bioengn & Nanotechnol, Ctr Theoret & Computat Mol Sci, Australia.
    Kaewmaraya, Thanayut
    Khon Kaen Univ, Dept Phys, Integrated Nanotechnol Res Ctr, Khon Kaen, Thailand; Nanotec KKU Ctr Excellence Adv Nanomat Energy Pro, Khon Kaen, Thailand.
    Chakraborty, Sudip
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Vovusha, Hakkim
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. King Abdullah Univ Sci & Technol, Phys Sci & Engn Div PSE, Thuwal, Saudi Arabia.
    Amornkitbamrung, Vittaya
    Khon Kaen Univ, Dept Phys, Integrated Nanotechnol Res Ctr, Khon Kaen, Thailand; Nanotec KKU Ctr Excellence Adv Nanomat Energy Pro, Khon Kaen, Thailand.
    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, Stockholm, Sweden.
    Defected and Functionalized Germanene-based Nanosensors under Sulfur Comprising Gas Exposure2018In: ACS SENSORS, ISSN 2379-3694, Vol. 3, no 4, p. 867-874Article in journal (Refereed)
    Abstract [en]

    Efficient sensing of sulfur containing toxic gases like H2S and SO2 is of the utmost importance due to the adverse effects of these noxious gases. Absence of an efficient 2D-based nanosensor capable of anchoring H2S and SO2 with feasible binding and an apparent variation in electronic properties upon the exposure of gas molecules has motivated us to explore the promise of a germanene nanosheet (Ge-NS) for this purpose. In the present study, we have performed a comprehensive computational investigation by means of DFT-based first-principles calculations to envisage the structural, electronic, and gas sensing properties of pristine, defected, and metal substituted Ge-NSs. Our initial screening has revealed that although interaction of SO2 with pristine Ge-NSs is within the desirable range, H2S binding however falls below the required values to guarantee an effective sensing. To improve the binding characteristics, we have considered the interactions between H2S and SO2 with defected and metal substituted Ge-NS. The systematic removals of Ge atoms from a reasonably large super cell lead to monovacancy, divacancies, and trivacancies in Ge-NS. Similarly, different transition metals like As, Co, Cu, Fe, Ga, Ge, Ni, and Zn have been substituted into the monolayer to realize substituted Ge-NS. Our van der Waals corrected DFT calculations have concluded that the vacancy and substitution defects not only improve the binding characteristics but also enhance the sensing propensity of both H2S and SO2. The total and projected density of states show significant variations in electronic properties of pristine and defected Ge-NSs before and after the exposure to the gases, which are essential in constituting a signal to be detected by the external circuit of the sensor. We strongly believe that our present work would not only advance the knowledge towards the application of Ge-NS-based sensing but also provide motivation for the synthesis of such efficient nanosensor for H2S and SO2 based on Ge monolayer.

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