Theoretical study of the heats of formation of small silicon-containing compounds

Heats of formation for nine small silicon-containing molecules were obtained from large basis set ab initio calculations using coupled cluster theory with a perturbative treatment of triple excitations. After adjusting the atomization energies for the finite basis set truncation error, core/valence correlation, scalar relativistic, higher order correlation, and atomic spin-orbit effects, the theoretical and experimental 0 K values of Delta H-f values were in good agreement. Using 106.6 kcal/mol as the heat of formation of silicon, we obtain Delta H-f values of SiH = 87.7 +/- 0.4 vs 89.5 +/- 0.7 (expt); SiH2((1)A(1)) = 64.1 +/- 0.4 vs 65.5 +/- 0.7 (expt); SiH2(B-3(1)) = 85.4 +/- 0.4 vs 86.5 +/- 0.7 (expt); SiH3 = 47.3 +/- 0.5 vs 47.7 +/- 1.2 (expt); SiH3 = 8.7 +/- 0.6 vs 9.5 +/- 0.5 (expt); Si-2 = 138.8 +/- 0.3 vs 139.2 (expt); Si2H6 = 19.7 +/- 0.5 vs 20.9 +/- 0.3 (expt); SiF = -14.8 +/- 0.4 vs -5.2 +/- 3 (expt); SiF2 = -151.7 +/- 0.5 vs -140.3 +/- 3 (expt); and SiF4 = -384.5 +/- 0.9 vs -384.9 +/- 0.2 (expt). Based on the present work, we suggest a number of revisions in the interpretation of the experimental data. Although a revision in Delta H(f)degrees(Si) to 107.4 +/- 0.6 kcal/mol at 0 K leads to improved agreement between theory and experiment for the SixHy compounds, it worsens agreement for SiF4. Given the remaining uncertainties in the theoretical approach, more definitive conclusions do not appear to be warranted.