AB-INITIO STUDY OF THE REACTIONS OF ZN(S-1, P-3, AND P-1) WITH SIH4

The reactions of Zn(S-1, P-3, and P-1) with SiH4 have been studied thr ough multiconfigurational self-consistent field (with relativistic eff ective core potentials) followed by extensive variational and perturba tional second-order multireference Moller-Plesset configuration intera ction by perturbation selected by iterative process calculations using extended Gaussian basis sets. The Zn atom in the P-3(4s(1)4p(1)) stat e breaks the Si-H bond of silane spontaneously, leading directly to th e ZnH+SiH3 final products, in agreement with experimental results. The P-1(4s(1)4p(1)) Zn atom is also inserted in the Si-H bond and the cor responding interaction surface shows an avoided crossing with the lowe st-lying X (1)A' potential surface, adiabatically correlated with the Zn(S-1:4s(2))+SiH4 reactants. This interaction leads also to the ZnH+S iH3 products. The structure of the HZnSiH3 intermediate product was ca refully studied as well as the dissociation channels leading to the Zn H+SiH3 and H+ZnSiH3 products. Accurate energy differences between thes e species are also reported. The qualitative difference in the behavio r of the 3P(4s(1)4p(1)) Zn reaction with methane and silane has been e xplained by analyzing the corresponding potential energy surfaces; the present results confirm the C-H bond steric hindrance hypothesis adva nced by Wang et al. [J. Chem. Phys. 104, 9401 (1996)]. (C) 1997 Americ an Institute of Physics. [S0021-9606(97)03441-7].