On the heat of formation of C5 and higher carbon clusters

Abstract

The heat of formation of C5 has been computed ab initio using a variation on G1 theory. The computed H = 251.7 ± 4 kcal/mol disagrees quite appreciably with the third-law measurements of Drowart et al.; however, the cause of this is shown to be in the use of very approximate free energy functions by these authors. Using better free energy functions leads to a revised experimental value of 253.3±5.8 kcal/mol, in excellent agreement with our ab initio value. A revision of previous estimates for C6 to C10 by Raghavachari and Binkley is presented.