Classical and Inverted Structures of SiX_nH_3-nLi and SiX_nH_3-nNa

Abstract

Geometry, energetics, and dipole moments of tetrahedral-like (classical) and inverted forms of SiXnH3-nLi and SiXnH3-nNa, where X stands for a halogen atom, are studied ab initio at HF, MP2, QCISD(T), and B3LYP levels of the theory using triple-ζ plus polarization and diffuse functions basis sets. The inverted form is found to be the most stable for all the cases where Li is present but not in all the cases involving Na. Energy differences between classical and inverted forms range from −2 to 24 kcal mol-1. The results for SiH3Li agree with previous data. Agreement of the properties determined using this methodology with the experimental results, where available, is found very satisfactory. An analysis of the bonding in these molecules in terms of atomic charges and electron density is carried out.