RHF and DFT Study of the Molecular and Electronic Properties of (SiO2)n and (GeO2)n Nanoclusters

Abstract

The study of nanoclusters has attracted a lot of scientific research over the years. This class of materials are important because they bridge the gap between bulk materials and molecular structures. Silicon and Germanium oxides have many applications in semiconductor technology and nanotechnology. In this research work, molecular and electronic properties of Silicon and Germanium dioxide nanoclusters are studied. The results obtained reveal the comparative advantages and disadvantages of using any of the two oxides for particular applications. Restricted Hartree Fock and Density Functional Theory computations of the molecular and electronic properties of (SiO2)n and (GeO2)n nanoclusters (n = 1,..,6) are studied. Silicon dioxide clusters are found to have higher thermal energies and lower average bond lengths and are thus more stable than Germanium dioxide clusters. At n = 1, both nanoclusters are non-polar, but gradually become more polar with increase in n. The average polarizability, molecular hyperpolarizability and total thermal energies of the nanoclusters increases with increase in molecular size. Computed values of the electron affinities for (SiO2)n clusters agree with experimental results. Some of the most intense Infra Red vibrational motions observed in both molecules are anti-symmetric stretching of Si=O/Ge-O and chain in plane, symmetric stretching of the Si=O/Ge-O bonds and chain in plane and symmetric twisting/breathing of the chain(s) in plane. The two nanoclusters are also Raman active at some frequencies.