Conformational Energies and Structural Relaxation in Singly Bonded Silicon, Phosphorus and Sulfur-Compounds

Abstract

Conformational energy differences, structural relaxation and changes in bonding between different rotamers of silicon, phosphorus and sulfur compounds have been calculated by ab initio molecular orbital methods to permit systematic comparison between the compounds of first and second row elements. The results were obtained with polarized 3-21G and 4-31G basis sets on the series SiH₃X, PH₂X and SHX (X = BH₂, CH₃, NH₂ and OH) and also on the rotamers of the second row hydrides Si₂H₆, P₂H₄ and S₂H₂. Bond length and bond angle relaxation and conformational energy differences for the Si -, P- and S-containing molecules are 30-50% smaller than in the compounds of the first row elements.