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Houmad, M., Essaoudi, I., Ainane, A., El Kenz, A., Benyoussef, A. & Ahuja, R. (2019). Improving the electrical conductivity of Siligraphene SiC7 by strain. Optik (Stuttgart), 177, 118-122
Open this publication in new window or tab >>Improving the electrical conductivity of Siligraphene SiC7 by strain
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2019 (English)In: Optik (Stuttgart), ISSN 0030-4026, E-ISSN 1618-1336, Vol. 177, p. 118-122Article in journal (Refereed) Published
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.

Keywords
Semiconductors, Biaxial strains, Siligraphene g-SiC7, Electrical conductivity
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-371032 (URN)10.1016/j.ijleo.2018.08.123 (DOI)000450136600015 ()
Available from: 2019-01-07 Created: 2019-01-07 Last updated: 2019-01-07Bibliographically approved
Cheng, K., Guo, Y., Han, N., Jiang, X., Zhang, J., Ahuja, R., . . . Zhao, J. (2018). 2D lateral heterostructures of group-III monochalcogenide: Potential photovoltaic applications. Applied Physics Letters, 112(14), Article ID 143902.
Open this publication in new window or tab >>2D lateral heterostructures of group-III monochalcogenide: Potential photovoltaic applications
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2018 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 112, no 14, article id 143902Article in journal (Refereed) Published
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%.

Place, publisher, year, edition, pages
AMER INST PHYSICS, 2018
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-352696 (URN)10.1063/1.5020618 (DOI)000429344100038 ()
Available from: 2018-06-08 Created: 2018-06-08 Last updated: 2018-06-08Bibliographically approved
Minakshi, M., Watcharatharapong, T., Chakraborty, S. & Ahuja, R. (2018). A combined theoretical and experimental approach of a new ternary metal oxide in molybdate composite for hybrid energy storage capacitors. APL MATERIALS, 6(4), Article ID 047701.
Open this publication in new window or tab >>A combined theoretical and experimental approach of a new ternary metal oxide in molybdate composite for hybrid energy storage capacitors
2018 (English)In: APL MATERIALS, ISSN 2166-532X, Vol. 6, no 4, article id 047701Article in journal (Refereed) Published
Abstract [en]

Sustainable energy sources require an efficient energy storage system possessing excellent electrochemical properties. The better understanding of possible crystal configurations and the development of a new ternary metal oxide in molybdate composite as an electrode for hybrid capacitors can lead to an efficient energy storage system. Here, we reported a new ternary metal oxide in molybdate composite [(Mn1/3Co1/3Ni1/3)MoO4] prepared by simple combustion synthesis with an extended voltage window (1.8 V vs. Carbon) resulting in excellent specific capacity 35 C g−1 (58 F g−1) and energy density (50 Wh kg−1 at 500 W kg−1) for a two electrode system in an aqueous NaOH electrolyte. The binding energies measured for Mn, Co, and Ni 2p are consistent with the literature, and with the metal ions being present as M(II), implying that the oxidation states of the transition metals are unchanged. The experimental findings are correlated well through density functional theory based electronic structure calculations. Our reported work on the ternary metal oxide studies (Mn1/3Co1/3Ni1/3)MoO4 suggests that will be an added value to the materials for energy storage.

National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-355692 (URN)10.1063/1.4994750 (DOI)000431141500010 ()
Available from: 2018-07-04 Created: 2018-07-04 Last updated: 2018-07-04Bibliographically approved
Long, D., Li, M., Meng, D., He, Y., Yoon, I. T., Ahuja, R. & Luo, W. (2018). Accounting for the thermo-stability of PdHx (x=1-3) by density functional theory. International journal of hydrogen energy, 43(39), 18372-18381
Open this publication in new window or tab >>Accounting for the thermo-stability of PdHx (x=1-3) by density functional theory
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2018 (English)In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 43, no 39, p. 18372-18381Article in journal (Refereed) Published
Abstract [en]

We calculate the formation enthalpies of PdHx (x = 0-3) by cluster expansion (CE) and calculations based on density functional theory. CE predicts the stable palladium hydride structures PdH, PdH2.62, and PdH2.75. The band structures and density of states indicate that the amount of hydrogen in the palladium lattice does not alter the metallic character of the palladium significantly. However, all PdH X structures with x > 1 have greater formation enthalpies than that of the given reaction path 4PdH(2) = 2PdH + 2Pd + 3H(2) and thus they are thermodynamically unstable. The shorter bond length of Pd-H and the smaller bond angle of Pd-H-Pd imply a higher cohesive energy in zincblende (ZB) PdH than that in rocksalt (RS) PdH. Bader charge analysis shows a stronger electronegativity of H atoms in ZB-PdH than that in RS-PdH. This results in a stronger Pd-H bond in ZB-PdH than that in RS-PdH. Thus ZB-PdH has lower formation enthalpy than that of RS-PdH. However, regarding the dynamic stability, we conclude that hydrogen atoms prefer to occupy the octahedral sites of the palladium lattice because of the lower zero-point energy and vibration free energy than that of occupying the tetrahedral sites. 

Place, publisher, year, edition, pages
PERGAMON-ELSEVIER SCIENCE LTD, 2018
Keywords
PdHx, Cluster expansion method, Density functional theory, Formation enthalpy, Thermodynamic stability, Dynamic stability
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-368759 (URN)10.1016/j.ijhydene.2018.08.030 (DOI)000446949400032 ()
Available from: 2018-12-07 Created: 2018-12-07 Last updated: 2018-12-07Bibliographically approved
Singh, D., Gupta, S. K., Sonvane, Y., Hussain, T. & Ahuja, R. (2018). Achieving ultrahigh carrier mobilities and opening the band gap in two-dimensional Si2BN. Physical Chemistry, Chemical Physics - PCCP, 20(33), 21716-21723
Open this publication in new window or tab >>Achieving ultrahigh carrier mobilities and opening the band gap in two-dimensional Si2BN
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2018 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 20, no 33, p. 21716-21723Article in journal (Refereed) Published
Abstract [en]

Recently, a two-dimensional (2D) Si2BN monolayer material made of silicon, boron and nitrogen, was theoretically predicated and has attracted interest in the scientific community. Due to its 2D planar nature with high formation energy, Si2BN monolayers can be flexible and strong like graphene and also exhibit captivating properties like those of other 2D materials. Motivated by this fascinating graphene-like monolayer of Si2BN, we have investigated its structural and electronic properties based on first-principles calculations. The electronic band structure of pure Si2BN shows metallic behaviour. We have discovered that the band gap of Si2BN monolayer can be tuned to 102 meV by applying external electric fields and mechanical strain. The band gap opening occurs at 5% strain, where the bond angles between the nearest neighbours become nearly equal. The band gap opening occurs at a small external electric field of 0.4 V angstrom(-1). More interestingly, at room temperature, the electron mobility of Si2BN is 4.73 x 10(5) cm(2) V-1 s(-1), which is much larger than that of graphene, while the hole mobility is 1.11 x 10(5) cm(2) V-1 s(-1), slightly smaller than the electron mobility. The ultrahigh carrier mobility of Si2BN may lead to many novel applications in high-performance electronic and optoelectronic devices. These theoretical results suggest that the Si2BN monolayer exhibits multiple effects that may significantly enhance the performance of Si2BN based electronic devices.

National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-366153 (URN)10.1039/c8cp03617a (DOI)000443280900050 ()30102304 (PubMedID)
Available from: 2018-11-20 Created: 2018-11-20 Last updated: 2018-11-20Bibliographically approved
Hussain, T., Vovusha, H., Kaewmaraya, T., Amornkitbamrung, V. & Ahuja, R. (2018). Adsorption characteristics of DNA nucleobases, aromatic amino acids and heterocyclic molecules on silicene and germanene monolayers. Sensors and actuators. B, Chemical, 255, 2713-2720
Open this publication in new window or tab >>Adsorption characteristics of DNA nucleobases, aromatic amino acids and heterocyclic molecules on silicene and germanene monolayers
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2018 (English)In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 255, p. 2713-2720Article in journal (Refereed) Published
Abstract [en]

Binding of DNA/RNA nucleobases, aromatic amino acids and heterocyclic molecules on two-dimensional silicene and germanene sheets have been investigated for the application of sensing of biomolecules using first principle density functional theory calculations. Binding energy range for nucleobases, amino acids and heterocyclic molecules with both the sheets have been found to be (0.43-1.16 eV), (0.70-1.58 eV) and (0.22-0.96 eV) respectively, which along with the binding distances show that these molecules bind to both sheets by physisorption and chemisorption process. The exchange of electric charges between the monolayers and the incident molecules has been examined by means of Bader charge analysis. It has been observed that the introduction of DNA/RNA nucleobases, aromatic amino acids and heterocyclic molecules alters the electronic properties of both silicene and germanene nano sheets as studied by plotting the total (TDOS) and partial (PDOS) density of states. The DOS plots reveal the variation in the band gaps of both silicene and germanene caused by the introduction of studied molecules. Based on the obtained results we suggest that both silicene and germanene monolayers in their pristine form could be useful for sensing of biomolecules.

Keywords
Adsorption characteristics, DNA nucleobases, Aromatic amino acids, Heterocyclic molecules
National Category
Materials Engineering
Identifiers
urn:nbn:se:uu:diva-341967 (URN)10.1016/j.snb.2017.09.083 (DOI)000414686500032 ()
Funder
Swedish Research CouncilCarl Tryggers foundation StandUp
Available from: 2018-02-19 Created: 2018-02-19 Last updated: 2018-02-19Bibliographically approved
Das, S., Swain, D., Araujo, R. B., Shi, S., Ahuja, R., Row, T. N. G. & Bhattacharyya, A. J. (2018). Alloying in an Intercalation Host: Metal Titanium Niobates as Anodes for Rechargeable Alkali-Ion Batteries. Chemistry - An Asian Journal, 13(3), 299-310
Open this publication in new window or tab >>Alloying in an Intercalation Host: Metal Titanium Niobates as Anodes for Rechargeable Alkali-Ion Batteries
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2018 (English)In: Chemistry - An Asian Journal, ISSN 1861-4728, E-ISSN 1861-471X, Vol. 13, no 3, p. 299-310Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
WILEY-V C H VERLAG GMBH, 2018
Keywords
alloying, anode, intercalation, rechargeable battery, synergy
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-345713 (URN)10.1002/asia.201701602 (DOI)000424106500016 ()29280560 (PubMedID)
Funder
Swedish Research CouncilStandUp
Available from: 2018-03-14 Created: 2018-03-14 Last updated: 2018-03-14Bibliographically approved
Shukla, V., Araujo, R. B., Jena, N. K. & Ahuja, R. (2018). Borophene's tryst with stability: exploring 2D hydrogen boride as an electrode for rechargeable batteries. Physical Chemistry, Chemical Physics - PCCP, 20(34), 22008-22016
Open this publication in new window or tab >>Borophene's tryst with stability: exploring 2D hydrogen boride as an electrode for rechargeable batteries
2018 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 20, no 34, p. 22008-22016Article in journal (Refereed) Published
Abstract [en]

Graphene's emergence can be viewed as a positive upheaval in 2D materials research. Along the same line, the realization of a related elemental 2D material, borophene, is another breakthrough. To circumvent the stability issues of borophene, which is reported to have been synthesized on metallic substrates under extreme conditions, hydrogenation of borophene (otherwise called as borophane or hydrogen boride or boron hydride) has been a plausible solution, but only proposed computationally. A recent report (H. Nishino, T. Fujita, N. T. Cuong, S. Tominaka, M. Miyauchi, S. Iimura, A. Hirata, N. Umezawa, S. Okada, E. Nishibori, A. Fujino, T. Fujimori, S. Ito, J. Nakamura, H. Hosono and T. Kondo, J. Am. Chem. Soc., 2017, 139(39), 13761-13769) brings to fore its experimental realization. Our current study delves into the possibilities of employing this intriguing 2D hydrogen boride as anodes in Li/Na ion batteries. Using first-principles density functional theory methods, we computed relevant properties such as the ion (Li/Na) adsorption behavior, the possible pathways of ionic diffusion with the estimation of barriers as well as the theoretical specific capacities and average voltages to uniquely demonstrate that this material is of particular significance for battery applications. It is noted that the use of hydrogen boride leads to a high specific capacity of 861.78 mA h g(-1) for Li ions, which is remarkably higher than the value reported in relation to its computationally predicted structure. Furthermore, Na ion intercalation leads to negative voltage profiles, implying the unsuitability of 2D hydrogen boride for this particular ion. Our findings are timely and pertinent towards adding insightful details relevant to the progress of applications of 2D materials for energy storage.

Place, publisher, year, edition, pages
ROYAL SOC CHEMISTRY, 2018
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-369513 (URN)10.1039/c8cp03686a (DOI)000449394100021 ()30109880 (PubMedID)
Funder
Swedish Research CouncilCarl Tryggers foundation StandUp
Available from: 2018-12-17 Created: 2018-12-17 Last updated: 2019-01-05Bibliographically approved
Smazna, D., Rodrigues, J., Shree, S., Postica, V., Neubueser, G., Martins, A. F., . . . Mishra, Y. K. (2018). Buckminsterfullerene hybridized zinc oxide tetrapods: defects and charge transfer induced optical and electrical response. Nanoscale, 10(21), 10050-10062
Open this publication in new window or tab >>Buckminsterfullerene hybridized zinc oxide tetrapods: defects and charge transfer induced optical and electrical response
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2018 (English)In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 10, no 21, p. 10050-10062Article in journal (Refereed) Published
Abstract [en]

Buckminster fullerene (C-60) based hybrid metal oxide materials are receiving considerable attention because of their excellent fundamental and applied aspects, like semiconducting, electron transfer, luminescent behaviors, etc. and this work briefly discusses the successful fabrication of C-60 decorated ZnO tetrapod materials and their detailed structure-property relationships including device sensing applications. The electron microscopy investigations indicate that a quite dense surface coverage of ZnO tetrapods with C-60 clusters is achieved. The spectroscopy studies confirmed the identification of the C-60 vibrational modes and the C-60 induced changes in the absorption and luminescence properties of the ZnO tetrapods. An increased C-60 concentration on ZnO results in steeper ZnO bandgap absorption followed by well-defined free exciton and 3.31 eV line emissions. As expected, higher amounts of C-60 increase the intensity of C-60-related visible absorption bands. Pumping the samples with photons with an energy corresponding to these absorption band maxima leads to additional emission from ZnO showing an effective charge transfer phenomenon from C-60 to the ZnO host. The density of states model obtained from DFT studies for pure and C-60 coated ZnO surfaces confirms the experimental observations. The fabricated C-60-ZnO hybrid tetrapod based micro- and nanodevices showed interesting ethanol gas sensing characteristics.

National Category
Condensed Matter Physics Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-357683 (URN)10.1039/c8nr01504j (DOI)000434313200027 ()29781017 (PubMedID)
Funder
EU, Horizon 2020Swedish Research Council, 2016-06014
Available from: 2018-08-20 Created: 2018-08-20 Last updated: 2018-08-20Bibliographically approved
Li, J., He, X., Peng, C. & Ahuja, R. (2018). Chemical Bonding of Unique CO on Fe(100). The Journal of Physical Chemistry C, 122(16), 9062-9074
Open this publication in new window or tab >>Chemical Bonding of Unique CO on Fe(100)
2018 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 122, no 16, p. 9062-9074Article in journal (Refereed) Published
Abstract [en]

At low coverage, CO molecules are known to preferentially occupy the hollow sites of Fe(100) with considerably inclined molecular orientations. This CO configuration serves as the precursor state of CO dissociation, which is particularly important in several important catalytic reactions. In this study, we present a unique bonding picture of the precursor state from the spin, charge, and orbital perspectives. From the spin and orbital views, we show the antiferromagenetic nature of the adsorbate–metal coupling, where 2π magnetism prevails with a dominant spin-down channel. However, contrasting tendencies are found for the two 1π orbitals in two orthogonal directions: the 1π orbital in the vertical plane loses its symmetry, whereas the other 1π orbital remains intact with a preserved symmetry. The 1π symmetry in the vertical plane favors the 1π → 2π* excitation mechanism owing to the partial opening up of the 1π symmetry. In the charge perspective, we have identified a charge transfer mechanism involving the local structural IFeC–C–O motif, in which the surface slightly charges the adsorbate with additional partial electrons located at the surface Fe atoms bonded to the carbon end, whereas the charges of the metallic atoms beneath the IFeC–C–O motif are found to be depleted. In both the adsorbate and metal sides, the depletion of s electrons serves as a good measure of orbital repulsion and delocalization. Interestingly, the carbon and oxygen ends exhibit contrasting electron affinity with the metal surface: the carbon end is attractive, whereas the oxygen end is repulsive in terms of the contrasting charge rearrangement in the bonded metallic atoms.

National Category
Theoretical Chemistry Physical Chemistry Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-356094 (URN)10.1021/acs.jpcc.8b01825 (DOI)000431151200041 ()
Available from: 2018-07-19 Created: 2018-07-19 Last updated: 2018-07-19Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0003-1231-9994

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