Structure of disiloxane: A semiempirical and Post-Hartree–Fock study

The semiempirical (MNDO, AM1, and PM3) and ab initio predicted structure of disiloxane is studied with a series of basis sets and inclusion of electron correlation at MP2, MP3, MP4, CCD, CCSD, and CCSD(T) levels. The calculated molecular geometry and barrier to linearization of the Si? O? Si bond angle are compared with previous theoretical and experimental values. Our results show that the calculated barrier to linearization is very sensitive to the number of polarization functions in the basis set. We also investigate the coupling between the Si? O? Si bond angle and the Si? O bond length and calculate the Mulliken and electrostatic potential-derived charges. For comparison purposes we also calculate the molecular geometry, the barrier to linearization of the Si? O? Si bond angle, and the atomic charges in hexamethyldisiloxane. © 1994 by John Wiley & Sons, Inc.