THEORETICAL ENTHALPIES OF FORMATION FOR SMALL SILICON HYDRIDES

Enthalpies of formation (DELTA-f-H-298) and Gibbs functions of formation (DELTA-f-G-298) for 27 molecular systems with up to three silicon atoms were calculated with high-quality electronic structure methods (multiconfigurational reference wave functions, singles-doubles configuration interaction) in combination with empirical bond enthalpy corrections. Estimates of (DELTA-f-H-298) values for selected molecules with four and five silicon atoms were obtained by extrapolation. With this set of theoretical enthalpy values we calculated singlet-triplet splittings, bond strengths of Si-H and Si-Si bonds, and reaction enthalpies of reactions of importance in the chemical vapor deposition of silicon from silanes. Furthermore, the influence of silyl substitution on the stability of triplet states and on Si-H and Si-Si bond strengths was investigated.