HEATS OF FORMATION OF SIHNO AND SIHNO2 CALCULATED BY AB-INITIO MOLECULAR-ORBITAL METHODS AT THE G-2 LEVEL OF THEORY

To help facilitate the study of the energetics and the mechanism of silane combustion and the oxidation of related silicon species, H(m)Si-OH(n), H(m)O-SiH(n)-OH(p), and H(m)Si-O-OH(n) have been examined by ab initio molecular orbital methods. Geometries have been optimized at the MP2/6-31G(d) level of theory, and vibrational frequencies have been computed at HF/6-31G(d). Heats of formation have been calculated at the G-2 level of theory (estimated mean absolute error of +/-2 kcal/mol or less). The following theoretical heats of formation (at 298 K) have been obtained: SiO, -22.6; HSiO, 8.5; SiOH, 0.1; H2SiO, -23.5; HSiOH, -23.7; H3SiO, 1.0; H2SiOH, -25.6; H3SiOH, -67.5; OSiO, -66.2; OSiHO, -37.7; OSiOH, -72.9; OSiH2OBAR, -28.1; OSiHOH, -110.6; HOSiOH, -117.5; OSiH2OH, -79.8; HOSiHOH, -104.2; HOSiH2OH, -149.0; HSiOO, 47.7; SiOOH, 23.7; H2SiOO, 35.5; HSiOOH, 0.2; H3SiOO, -2.7; H2SiOOH, 1.1; H3SiOOH, -41.4 kcal/mol.