Electronic structure and vibrational spectra of X20H20 (X=C, Si, Ge, Sn): A theoretical study

Optimized geometries, HOMO-LUMO gaps, vertical ionization potentials and electron affinities are obtained using HF, and B3LYP methods with 6-311G** basis set for C20H20, Si20H20 and Ge20H20. For germanium and tin analogues, B3LYP calculations are performed with LANL2DZ effective core potential. Electron correlation is included by doing MP2 calculation. The harmonic frequencies of all the compounds are obtained using B3LYP with 6-311G** and/or LANL2DZ basis sets. The force field and vibrational spectra are analyzed and 74 symmetry unique non-redundant local force constants are evaluated. Probable assignments are proposed for all the fundamentals based on the potential energy distribution.