Electronic structure studies on silylalkanes, alkylsilanes and silysilanes

Abstract

The authors report ab initio calculations on the H, C, Si cluster molecules Si2H6, C2H6, SiH3CH3, Si5H12, (SiH3)4C, (CH3)4Si and C5H12. The method involved the use of pseudopotentials to replace the Si core. Total energy differences show that, at least at the SCF level of theory, Coulombic stabilisation largely compensates for loss of maximal overlap, thus rendering the C-Si bond very slightly stable against disproportionation. The orbital energy changes and charge populations imply that bonding differences can be understood very largely in terms of local interactions, so that the delocalisation properties occurring in silanes must arise from second-order interactions involving relatively low-lying excited states. The tetrasilyl methane molecule is predicted to be rather stable.