Optimized parameters for scaling correlation energy

Twelve general parametrizations of the SAC (scaling-all-correlation) method for semiempirical extrapolation of electronic structure calculations are p resented. The methods are based on Moller-Plesset perturbation theory and c oupled-cluster theory with correlation-consistent basis sets, and the param etrizations are based on 49 equilibrium atomization energies. This paper al so presents an optimized scale factor for estimating the total anharmonic z ero-point vibrational energy of a molecule with a root-mean-square accuracy of 0.17 kcal/mol.