Theoretical study of the GemSin (m + n = 3) clusters

摘要

The main objective of this study consists in providing reliable structures, harmonic vibrational frequencies, and relative electronic energies of Si 3, GeSi2, Ge2Si, and Ge3 clusters using DFT, CCSD(T), CASSCF, and MP2 methods and extended basis sets. The CCSD(T) results are extrapolation to the complete basis set (CBS) limit. For Si 3 cluster, the ground-state is a singlet (1A1) and the lowest lying electronic state is triplet state (3A′ 2) separated by 0.44 kcal mol-1 at the CCSD(T)/(CBS) limit. The ground-states of GeSi2, Ge2Si, and Ge 3 clusters are also singlet state with triplet states very close energetically. Computed equilibrium geometries and vibrational frequencies are compared with previous theoretical and experimental data.