Department of Physics
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Item Hydrogen storage on MgO supported TiMgn (n = 2–6) clusters: a first principle investigation(Elsevier, 2024-08) Bandyopadhyay, DebashisThe current study explores the potential of MgO-supported finite-sized TiMgn (n = 2–6) nanoclusters as hydrogen storage materials, employing density functional theory with a spin-polarized generalized gradient approximation (GGA). These systems' structural stability and electronic characteristics reveal that supported clusters offer superior hydrogen storage capabilities compared to their unassisted counterparts. Various parameters, including cluster-adsorption energy (Eads), hydrogen-adsorption energy in supported clusters (Eads-H), HOMO-LUMO gap, vertical ionization potential (VIP), vertical electron affinity (VEA), chemical potential (μ), and chemical hardness (ɳ) are computed. Substrate support notably enhances the thermodynamic stability and chemical reactivity of the TiMg5 cluster when contrasted with the bare TiMg5 cluster. Furthermore, a remarkable increase in the gravimetric hydrogen storage density, from 1.63 wt% for bare Mg5 clusters to 3.45 wt% for bare TiMg5 clusters, reaching 5.62 wt% in the supported TiMg5 cluster system is observed. These findings indicate the substrate-supported TiMg5 cluster as a promising candidate for hydrogen storage applications.Item The study of the electronic structures and properties of pure and transition metal-doped silicon nanoclusters: a density functional theory approach(Taylor & Francis, 2009-03) Bandyopadhyay, DebashisThis report presents the study of ab initio electronic structure and properties of pure and transition metal (TM = Ti, Zr and Hf)-doped silicon clusters, TM@Si(n), by using density functional theory with a polarised basis set (LanL2DZ) within the spin-polarised generalised gradient approximation for different values of n varying from 8 to 20. As the first step of the study, different optimised geometries of pure and doped clusters are calculated. These optimised clusters are then used to calculate different structural and physical parameters of the clusters, like binding energy, Highest Occupied Molecular Orbital – Lowest Unoccupied Molecular Orbital (HOMO–LUMO) gap, charge transfer, etc. In order to check the stability of the clusters, the second-order difference in the energy of the optimised structures is calculated. To study the optical behaviour of the clusters, infrared and Raman spectra are also calculated. Further calculations are also done on cation and anion clusters of both pure and doped nanoclusters to obtain their ionisation potential, electron affinity and chemical potential. An effort has been made to correlate the variation of different calculated parameters with the size of the clusters to explain the real existence and stabilities of different TM-doped clusters.Item The electronic structures and properties of transition metal-doped silicon nanoclusters: A density functional investigation(Elsevier, 2008-11) Bandyopadhyay, DebashisWe report an ab initio all electron molecular-orbital electronic-structure calculation by using density functional theory (DFT) and with polarized basis set (LanL2DZ) within the spin polarized generalized gradient approximation for metal-doped silicon clusters, SinM (n = 14–20 and M = Ti, Zr, Hf). As the first step of calculation, geometrical optimizations of the nanoclusters have been done. In the next step, these optimized geometries are used to calculate the binding energy and HOMO–LUMO gap (band gap) of the clusters. In order to check the dynamical stability of the clusters, IR and Raman spectra have been calculated. Further calculations have been done on cation and anion clusters to obtain ionization potential (IP), electron affinity (EA), chemical potential and chemical hardness of the optimized clusters.Item Study of adsorption and dissociation pathway of H2 molecule on MgnRh (n = 1–10) clusters: A first principle investigation(Elsevier, 2016-11) Bandyopadhyay, DebashisWe report the interaction of hydrogen molecule with MgnRh clusters using density functional formalism with an objective to study (a) the reactivity of small sized MgnRh clusters with H2 molecule and (b) the catalytic effect of Rh on the Mgn cluster for adsorption and dissociation of hydrogen. From the variation of thermodynamic parameters, adsorption and chemisorption etc. with the size of the cluster, we found that the most stable lowest energy structure in the series is Mg6Rh, whereas, Mg9Rh is the most effective hydrogen storage cluster. Interaction of H2 with MgnRh cluster shows a significant reduction in the activation barrier energy, which helps in the hydrogen dissociation. The chemisorptions energy reveals that Mg9Rh cluster act as an effective catalytic agent for hydrogen adsorption and dissociation. The calculated activation barrier energy of H2single bondMg9Rh has been verified by the study of intrinsic reaction coordinates (IRC) pathway between Mg9Rh and H2.Item Highly sensitive fluorescent imidazolium-based sensors for nanomolar detection of explosive picric acid in aqueous medium(Elsevier, 2016-06) Pant, Debi D.; Sakhuja, RajeevTwo novel fluorescent coumaryl linked imidazolium salts have been synthesized, characterized and found to be highly selective for nanomolar detection of commonly used explosive picric acid, over other aromatic explosives in aqueous medium. The compounds are highly photostable and are practically applicable for sensing picric acid in real environmental samples, in presence of interfering aromatic/non-aromatic explosives and metal ions. In solution, the high sensitivity of the sensors toward picric acid can be predominantly attributed to the ground-state charge-transfer complex formation based on UV–vis studies, time resolved fluorescence results and DFT calculations.