QUANTUM MONTE-CARLO BINDING-ENERGIES FOR SILICON HYDRIDES

Variational and diffusion Monte Carlo calculations are carried out on the molecules SiHn (n = 1-4), Si-2, Si2H6, and Si3H8. The anion SiH3- is also considered. Core electrons are eliminated through the use of a n ab initio effective core potential. The atomization energies and var ious bond energies are compared with experiment and other calculations . The atomization energies of SiH-SiH4 are in good agreement with expe riment and with the best other calculations. The calculated electron a ffinity of SiH3 is within 0.02 eV of the measured value. The calculate d atomization energies of the silanes SiH4, Si2H6, and Si3H8 are more consistent with the original heats of formation of Gunn and Green [J. Phys. Chem. 65, 779 (1961); 68, 946 (1964)], without the subsequent co rrections [M. W. Chase, Jr., C. A. Davies, J. R. Downey, Jr., D. J. Fr urip, R. A. McDonald, and A. N. Syverud, J. Phys. Chem. Ref. Data 14, Suppl. 1 (1985)] made on the assumption that the final state of Si is amorphous. (C) 1997 American Institute of Physics.