An ab initio investigation of disiloxane using extended basis sets and electron correlation

The ab initio structure of disiloxane (H₃Si-O-SiH₃) is studied with a series of basis sets of increasing quality, including extended basis sets and explicit electron correlation at the single-reference single- and double-excitation configuration interaction (SDCI) level. The calculated molecular geometry and barrier to linearization of the Si-O-Si bond angle are compared to experimental and previous theoretical values. Results show that the rigorous expansion of the basis set leads to a good agreement with experimental data at the restricted Hartree-Fock (RHF) level. The potential energy curves and force constants for variation of the Si-O-Si angle and the Si-H and Si-O bond lengths are calculated and discussed in relationship to molecular modeling of zeolites and clays. We also investigate coupling between the Si-O bond and Si-O-Si bond angle. We discuss the effects of temperature on the comparison between theoretical and experimental results.