On the calculation of atomization energies of organic molecules in the Xα local spin density approximation

Abstract

The atomization energies of selected alkanes, alkyl radicals, and amines are deduced from Xa local spin densitycalculations of E, the total energy of a molecule in its potential minimum. Both the exchange-correlation energy, a(aE/au), and aE/au itself obey, in a first approximation, simple atom-by-atom additivity rules. The appropriate a's for use in Xa(LSD) calculations of organic molecules thus appear as weighted averages and depend on the particular composition of each molecule. The at least approximate validity of this averaging procedure is illustrated by the accuracy of calculated atomization energies.

Xα local spin density calculations of the 1:1 hydrogen-bonded complexes formed by water, ammonia, and hydrogen fluoride

“…As regards organic molecules, the LCGTO-Xa(LSD) method was recently tested (5) in calculations of their total (kinetic + potential) energies, using the computational technology developed by Dunlap, Connolly, and Sabin (6). The attempt was a successful one: calculated energies were generally well within experimental uncertainties.…”

“…. , ni atoms A, B, etc., in which case ai and aEi/aa represent atomic parameters (5). Note that eqs.…”