Department of Physics

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Subject: search.filters.subject.Binding energy (BE)

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Now showing 1 - 7 of 7
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    Insights into the electronic structure and stability of TiMgn (n = 1–12) clusters: Validation of electron counting rule
    (Elsevier, 2022-08) Bandyopadhyay, Debashis
    The present study reports the investigation of the electronic structure and stability of TiMgn (n = 1–12) nanoclusters in the framework of the linear combination of atomic orbital density functional theory (DFT) together with a spin-polarized generalized gradient approximation (GGA). We have calculated different thermodynamic and chemical parameters, such as binding energy (BE), embedding energy (EE), fragmentation energy (FE), HOMO-LUMO gap, vertical ionization potential (VIP), vertical electron affinity (VEA), etc. during the growth process of the cluster to understand their stability. From the study, the TiMg8 cluster comes out to be the most stable cluster. Further, the positive charge (Mulliken charge) on the Ti in TiMg8 cluster indicates that the Mg8-cage behaves as an electron acceptor during hybridization with the Ti. The absence of any reactive site (obtained from NBO), minimum Mg-Ti bond length, and negative NICS in TiMg8 ground state cluster support it as a globally stable cluster. Low ELF index value revealing the non-reactivity of the TiMg8 cluster. Finally, orbital analysis shows that TiMg8 clusters follow closed-cell electronic orbital sequence 1S21P61D102S2 and satisfy the 20-electron counting rule. IR and Raman spectrum calculations are also presented to understand the vibrational nature of the clusters.
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    Effect of Transition Metal Doping on Hydrogenated Germanium Nanocages: A Density Functional Investigation
    (American Scientific Publishers, 2010-01) Bandyopadhyay, Debashis
    In this report we present an ab initio electronic-structure calculations of hydrogenated germanium cages GenHnTM (TM = Cu and Zn, n = 12 to 24) using density functional theory with polarized basis set (SDD) nanoclusters. In the first step of the calculation, geometrical optimizations of the nanoclusters have been done. In the next step only the ground state optimized geometries are used to calculate the binding energy (BE), HOMO-LUMO gap and embedding energy (EE) of the clusters. Based on these values a comparative study on different doping and also with respect to the pure cages are done. It is found that though the doping with Cu can be taken favorable in the cages, but Zn is not.
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    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, Debashis
    This 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.
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    Study of electronic structure, stabilities and electron localization behavior of AgPbn (n=1–14) nanoclusters: A first principal investigation
    (Elsevier, 2021-07) Bandyopadhyay, Debashis
    Present study reports the investigation of the electronic structure, stability and electron localization function (ELF) of endohedrally doped AgPbn clusters under frame work of density functional theory. From the variation of different thermodynamic and chemical parameters, such as, binding energy, embedding energy, fragmentation energy, chemical potential and chemical hardness, etc. during the growth process, we found that the AgPb10 and AgPb12 are relatively stable species. The density of states (DOS) explains that the strong p–d hybridization is responsible for the stability of these clusters. On the other hand, the bonding characteristics have been analyzed using electron localization function (ELF). The analysis of ELF in the most stable AgPb10 and AgPb12 clearly confirmed that the electrons are tending to localize on the outer side of the cage structure. Calculated HOMO-LUMO gaps of AgPb10 and AgPb12 clusters designate that these clusters could be useful as optical device in the visible region. Calculated IR and Raman spectrum show that the vibrational spectrum are in the far infrared region.
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    Chemisorptions effect of oxygen on the geometries, electronic and magnetic properties of small size Nin (n = 1-6) clusters
    (Springer, 2011-05) Bandyopadhyay, Debashis
    The present study reports the effect of oxygen addition on small size Nin (n = 1-6) clusters in different spin states within the framework of linear combination of atomic orbital (LCAO) density functional theory (DFT) under spin polarized generalized gradient approximation (GGA) functional. Relative stabilities of the optimized clusters are discussed on the basis of the calculated parameters, such as, binding energy (BE), embedding energy (EE) and fragmentation energy (FE). Other parameters, like ionization potential (IP), electron affinity (EA), etc. show that though the additions of oxygen can affect the chemical properties of Nin clusters with an additional stability to NinO. In most of the cases the magnetic moment of the stable isomers are geometry dependent for a particular size both in pure and oxidized clusters. Calculated magnetic moments of NinO (n = 1-6) clusters reveal that the magnetic moment of ground state Ni4O isomers in different geometries is same as in pure Ni4 isomers. Present study also explains the cause of stable magnetic moment in Ni4O cluster through the distribution of electrons in different orbitals.
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    The electronic structures and properties of transition metal-doped silicon nanoclusters: A density functional investigation
    (Elsevier, 2008-11) Bandyopadhyay, Debashis
    We 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.
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    Architecture, electronic structure and stability of TM@Ge(n) (TM = Ti, Zr and Hf; n = 1-20) clusters: a density functional modeling
    (Springer, 2012) Bandyopadhyay, Debashis
    The present study reports the geometry, electronic structure and properties of neutral and anionic transition metal (TM = Ti, Zr and Hf)) doped germanium clusters containing 1 to 20 germanium atoms within the framework of linear combination of atomic orbitals density functional theory under spin polarized generalized gradient approximation. Different parameters, like, binding energy (BE), embedding energy (EE), energy gap between the highest occupied and lowest unoccupied molecular orbitals (HOMO-LUMO), ionization energy (IP), electron affinity (EA), chemical potential etc. of the energetically stable clusters (ground state cluster) in each size are calculated. From the variation of these parameters with the size of the clusters the most stable cluster within the range of calculation is identified. It is found that the clusters having 20 valence electrons turn out to be relatively more stable in both the neutral and the anionic series. The sharp drop in IP as the valence electron count increases from 20 to 21 in neutral cluster is in agreement with predictions of shell models. To study the vibrational nature of the clusters, IR and Raman spectrum of some selected TM@Gen (n = 15,16,17) clusters are also calculated and compared. In the end, relevance of calculated results to the design of Ge-based super-atoms is discussed.