Computational Thermochemistry of Medium-Sized Silicon Hydrides

Abstract

Standard enthalpies ΔfH298, entropies S298, and Gibbs functions of formation ΔfG298 for a large number of silicon hydrides containing one to five Si atoms have been calculated. The choice of compounds includes cyclic and acyclic silanes, silyl radicals, silylenes, disilenes, and cyclic diradicals. The thermodynamic functions were calculated using an empirically corrected ab initio scheme. The electronic energies were obtained with multiconfiguration reference averaged coupled-pair functional (ACPF) wave functions. Two different basis sets were employed to demonstrate the validity of the correction scheme. The computed data are compared with experimental and theoretical data from other laboratories. Increment rules and substituent effects are presented and various reaction enthalpies are tabulated and discussed. The performance of the correction scheme and potential pitfalls in its general applicability are discussed.