Accurate Heats of Formation for SiFn and SiFn⁺, for n = 1−4

Accurate heats of formation are computed for SiF n and SiF n +, for n = 1−4. The vibrational frequencies are determined at the B3LYP level of theory. The energetics are determined at the CCSD(T) level of theory. Basis set limit values are obtained by extrapolation. In those cases where the CCSD(T) calculations become prohibitively large, the basis set extrapolation is performed at the MP2 level. The temperature dependence of the heat of formation, heat capacity, and entropy are computed for the temperature range 300−4000 K and fit to a polynomial. The CCSD(T) bond energies are compared with those obtained at the B3LYP, MP2, G2, and G2MP2 levels of theory.