HEATS OF FORMATION OF ALKANES CALCULATED BY DENSITY-FUNCTIONAL THEORY

The heats of formation for alkanes can be calculated using density functional theory with the accuracy comparable to that obtained by ab initio Hartree-Fock and second-order many-body perturbation theory (MBPT[2] vel MP2) calculations. The density functional approach not only accounts for the correlation energy (though in approximate manner) but is much faster than comparable MBPT[2] calculations. The set of equivalents for C-H and C-C bonds and methyl, iso, and neo arrangements was derived from the experimental heats of formation for 12 molecules. These equivalents combined with the calculated total energy and simple statistical mechanical corrections yield values of heats of formation which are in excellent agreement with experimental data.