A definitive heat of vaporization of silicon through benchmark ab initio calculations on SiF4

In order to resolve a significant uncertainty in the heat of vaporization of silicon — a fundamental parameter in gas-phase thermochemistry — ∆H◦ f,0[Si(g)] has been determined from a thermochemical cycle involving the precisely known experimental heats of formation of SiF4(g) and F(g) and a benchmark calculation of the total atomization energy (TAE0) of SiF4 using coupled-cluster methods. Basis sets up to [8s7p6d4f2g1h] on Si and [7s6p5d4f3g2h] on F have been employed, and extrapolations for residual basis set incompleteness applied. The contributions of inner-shell correlation (−0.08 kcal/mol), scalar relativistic effects (−1.88 kcal/mol), atomic spinorbit splitting (−1.97 kcal/mol), and anharmonicity in the zero-point energy (+0.04 kcal/mol) have all been explicitly accounted for. Our benchmark TAE0=565.89±0.22 kcal/mol leads to ∆H ◦ f,0[Si(g)]=107.15±0.38 kcal/mol (∆H◦ f,298[Si(g)]=108.19±0.38 kcal/mol): between the JANAF/CODATA value of 106.5±1.9 kcal/mol and the revised value proposed by Grev and