Prachi Pradhan | Searcharxiv

arXiv2005

A Hybrid Density Functional Study of Armchair Si and Ge Nanotubes

First principles calculations based on hybrid density functional theory have been used to study the electronic and geometric properties of armchair silicon and germanium nanotubes ranging from A (3, 3) through A (9, 9). The approach used is the finite cluster approach with hydrogen termination to simulate the effects of longer tubes. A detailed comparison of the structures and stabilities of Si and Ge nanotubes has been performed and the dependence of the HOMO- LUMO or band gaps on the tube diameters has been investigated. Silicon nanotubes appear to be less-puckered and more stable compared to germanium nanotubes. The largest silicon nanotube studied has a cohesive energy of 3.138eV/atom to be compared with the cohesive energy of 2.770eV/atom for the corresponding germanium nanotube. Contrary to some published results in the literature, silicon nanotubes do not appear to be metallic for the cases studied in the armchair configuration.

physics.atm-clus↗

arXiv2004

A Density Functional Study of the Structure and Energetics of Small Hetero-Atomic Silicon-Carbon Nanoclusters

The theoretical formalism of the local density approximation (LDA) to density functional theory (DFT) has been used to study the electronic and geometric structures of SimCn (1<=m, n<=4;n<=m) clusters. An all electron 6-311++G** basis set has been used and complete geometry optimizations of different possible structures for a particular cluster have been carried out. Clusters with equal numbers of silicon and carbon atoms are found to be particularly stable. Based on the simultaneous criteria of highest binding energy, high band gap, high ionization potential, and low electron affinity, we believe that Si3c3 is a candidate for particularly stable or a so-called "magic cluster". A complete comparison of the structures and the stabilities of the clusters, and their dependence on the cluster size and the stochiometry have been studied in detail. Binding energies, vibrational frequencies, HOMO-LUMO gaps, vertical ionization potentials and vertical electron affinities of the optimized clusters have been compared with other experimental and theoretical results available in the literature.

physics.atm-clus↗