Calculation of atomization energies by a multiconfigurational localized perturbation theory - Application for closed shell cases

In a recent publication [L. A. Curtiss et al., J. Chem. Phys. 106, 1063 (19 97)] the enthalpies of formation of 148 molecules are calculated via the Ga ussian-2 (G2) scheme, and compared to reliable experimental values. The set of molecules assembled can be used as a benchmark to test reliability of d ifferent theoretical models to predict thermochemical properties. The perfo rmance is impressive, with an average absolute deviation of only 1.58 kcal/ mol. We have developed an alternative model, the J2 model which is based on the generalized valence bond-localized Moller-Plesset (GVB-LMP2) method. I n this work the J2 model is tested by calculation of the enthalpies of form ation of closed shell molecules containing only first row atoms from the G2 set of molecules. This is achieved by using the GVB-LMP2 method to calcula te atomization energies and using experimental values to shift the energies to heats of formation. The J2 theory is shown to perform statistically bet ter than the much more expensive G2 method. This is shown not only by a low er mean absolute deviation but even more importantly by a lower maximum dev iation. The most dramatic improvement is obtained for the systems containin g carbon-fluoride bonds. An explanation for this result is presented. (C) 1 999 American Institute of Physics. [S0021-9606(99)30404-9].