Faculty Publications
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Item Semiconducting B13C2 system: Structure search and DFT-based analysis(Institute of Physics, 2019) Pillai, H.G.; Madam, A.K.; Chandra, S.; Cheruvalath, V.M.DFT calculation on Boron Carbide in B13C2 stoichiometry using a 15-atom unit cell necessarily results in metallic ground state regardless of the crystal structure. This is because such a unit cell consists of odd number of electrons, and hence complete filling of the top most band(s) of nonzero occupancy is impossible. This is in contrast to the observed semiconducting nature. If the crystal structure of B13C2 is made of a 30-atom unit cell which cannot be reduced to a 15 atom cell, there is a possibility of obtaining either a metallic or a semiconducting state as such a cell consists of an even number of electrons. In this work the evolutionary algorithm based structure search using 30-atom unit cells has yielded a previously unreported semiconducting system of B13C2 with unique bonding pattern. The mechanical and dynamical stability of the system have been properly established through the computation of elastic constants and phonon spectra. Its bond lengths, elastic moduli, hardness and infrared spectrum are in good agreement with experimental data. ©2019 IOP Publishing Ltd.Item Stone-Wales Defect Induced Performance Improvement of BC3 Monolayer for High Capacity Lithium-Ion Rechargeable Battery Anode Applications(American Chemical Society, 2020) Thomas, S.; Madam, A.K.; Asle Zaeem, M.A.First-principles density functional theory (DFT) computations were adopted to assess the potential application of a boron carbide (BC3) monolayer with point and topological defects as an anode material in alkali metal-based lithium (Li) ion rechargeable batteries. Results show that point defects (mono and bi vacancies) induce a large structural deformation upon Li intercalation which restricts their use for anode application. However, the Stone-Wales defect filled BC3 monolayer shows high structural stability with a negative Li binding energy of -1.961 eV in comparison with -0.930 eV of its pristine form. It is also noticed that after adsorbing the Li atom, the semiconducting characteristics of both the pristine and Stone-Wales defect filled BC3 monolayers are transformed into metallic, electrically conductive states. More importantly, the Li alkali metal atom shows fast diffusion on the surfaces of both the pristine and the Stone-Wales defect filled BC3 monolayers with low energy barriers of 0.34 and 0.33 eV, respectively. Besides, both the pristine and Stone-Wales defect filled BC3 monolayers exhibit high theoretical specific capacities of 1144 and 1287 mAhg-1, which are much higher than that of a traditional graphite anode and stand among the highest values of anode materials detailed in literature. The Li alkali metal intercalated monolayers BC3 show small average open-circuit voltages of 0.485 and 0.465 V for pristine and Stone-Wales defect cases, respectively. On the basis of the aforementioned details, the present study suggests that the Stone-Wales type topological defect incorporated BC3 monolayer is a promising anode material for Li-ion based rechargeable batteries with high storage capacity, low Li diffusion energy barrier, and low average open-circuit voltage. © 2020 American Chemical Society.