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Birabar Ranjit Kumar Nanda
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Birabar Ranjit Kumar Nanda
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Birabar Ranjit Kumar Nanda
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Nanda, Birabar Ranjit Kumar
Nanda, B. Ranjit K.
Nanda, Birabar R.K.
Nanda, B. R.K.
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5 results
Now showing 1 - 5 of 5
- PublicationVirtual synthesis of crystals using ab initio MD: Case study on LiFePO4(19-05-2017)
;Mishra, S. B.Molecular dynamics simulation technique is fairly successful in studying the structural aspects and dynamics of fluids. Here we study the ability of ab initio molecular dynamics (ab initio MD) to carry out virtual experiments to synthesize new crystalline materials and to predict their structures. For this purpose the olivine phosphate LiFePO4 (LFPO) is used as an example. As transition metal oxides in general are stabilized with layered geometry, we carried out ab initio MD simulations over a hypothetical layered configuration consisting of alternate LiPO2 and FeO2 layers. With intermittent steps of electron minimization, the resulted equilibrium lattice consist of PO4 tetrahedra and distorted Fe-O complexes similar to the one observed in the experimental lattice. - PublicationUniversality in the electronic structure of 3d transition metal oxides(01-12-2018)
;Parida, Priyadarshini ;Kashikar, Ravi ;Jena, AjitElectronic structure of strongly correlated transition metal oxides (TMOs) is a complex phenomenon due to competing interaction among the charge, spin, orbital and lattice degrees of freedom. Often individual compounds are examined to explain certain properties associated with these compounds or in rare cases few members of a family are investigated to define a particular trend exhibited by that family. Here, with the objective of generalization, we have investigated the electronic structure of three families of compounds, namely, highly symmetric cubic mono-oxides, symmetry-lowered spinels and less explored asymmetric olivine phosphates, through density functional calculations. From the results we have developed empirical hypotheses involving electron hopping, electron-lattice coupling, Hund's rule coupling, strong correlation and d-band filling. These hypotheses, classified through the point group symmetry of the transition metal - oxygen complexes, can be useful to understand and predict the electronic and magnetic structure of 3d TMOs. - PublicationOrigin of high stability, enhanced specific capacity, and low Li diffusion energy in boron doped Li3V2(PO4)3(01-10-2023)
;Gavali, Deepak S. ;Abhijitha, V. G.; Thapa, RanjitLi3V2(PO4)3 (LVP) is a well-known cathode material of Li-ion batteries, whereas the specific capacity is limited by the maximum Lithium (Li) de-intercalation probability associated with vacancy energy. The reason behind this limitation is not known yet, which needs to be address, and the modification needs to be done in the electronic structure to get a more specific capacity. In this work, using First-principles calculation, we have found that Li1 (the tetrahedra geometry) is having a higher Li vacancy energy as compared to Li2 and Li3, which limits the Li de-intercalation below x = 1.8, (where x is Li concentration). The change in bandgap of LVP structure after boron (B) substitution is directly correlated to the change in the oxygen (O) occupancy due to B substitution. As of comparing formation energy plot of pristine LVP and B substituted LVBP structure, we have found that in case of LVBP structure formation of x > 2 Li de-intercalation is possible, which help to enhance the specific capacity up to 205 mAh/g. Overall, we identify the cause of the less specific capacity of LVP and provide the solution by suggestion B doping, which also provides less Li diffusion barrier energy. - PublicationGraphdiyne - A Two-Dimensional Cathode for Aluminum Dual-Ion Batteries with High Specific Capacity and Diffusivity(23-08-2021)
;Mishra, Shashi B. ;V G, Abhijitha; Identifying a suitable cathode material for aluminum dual-ion batteries (ADIBs) with an enhanced specific capacity, cyclic durability, and open circuit voltage is among the major challenges in its commercialization. This study presents a graphdiyne (GDY) monolayer, a recently synthesized carbon allotrope, as a promising cathode material to host the diffusing AlCl4-, which is responsible for the charging/discharging process in ADIBs. Density functional theory calculations are performed to reveal the mechanism of adsorption of AlCl4 on GDY, while thermodynamical stability and diffusion dynamics are examined through ab initio molecular dynamics simulations. The theoretical specific capacity of this room-temperature stable system is calculated to be 186 mA h/g, which is 3 times higher compared to the case in which graphite is used as the cathode. The cyclic durability of this system is established as the GDY regains its equilibrium structure after releasing AlCl4 during discharge. The activation barrier - a measure of ease with which the diffusion occurs - is calculated with the aid of the climbing image-nudged elastic band method and found to be 0.08 and 0.05 eV for monolayer and bilayer GDY, respectively. Hence, with GDY as the cathode material, we can achieve an ultralow diffusion energy barrier. Furthermore, due to charge transfer between Cl and C sites, the semiconducting GDY becomes metallic upon AlCl4 adsorption, which is an added advantage in improving the electronic conductivity. - PublicationTailoring p-and n-type semiconductor through site selective oxygen doping in Cu3N: Density functional studies(01-06-2016)
;Sahoo, Guruprasad ;Kashikar, Ravi; Using ab initio density functional calculations, we have investigated the stability and electronic structure of pure and oxygen doped semiconducting Cu3N. The oxygen can be accommodated in the system without structural instability as the formation energy either decreases when oxygen substitutes nitrogen, or remains nearly same when oxygen occupies the interstitial position. The interstitial oxygen (OI) prefers to stabilize in the unusual charge neutral state and acts as an acceptor to make the system a p-type degenerate semiconductor. In this case the hole pockets are formed by the partially occupiedOI-p states. Onthe other hand, oxygen substituting nitrogen (OS) stabilizes in its usual2 charge state and acts as a donor to make the system an n-type degenerate semiconductor. The electron pockets are formed by the conducting Cu-p states. In the case of mixed doping, holes are gradually compensated by the donor electrons and an intrinsic gap is obtained for Cu3N1-2xO xO x S 2 I stoichiometry.Our calculations predict the nature of doping aswell as optical band gap (Eg ) opt variation in experimentally synthesized copper oxynitride. While interstitial doping contracts the lattice and increases the Eg , opt substitutional doping increases both lattice size and E . g opt Mixed doping reduces Eg . opt Additionally we show that a rare intra-atomic d-p optical absorption can be realized in the pristine Cu3Nas the Fermi level lies in the gap between the Cu-d dominated antibonding valence state and Cu-p conducting state.