Improved coefficients for the scaling all correlation and multi-coefficient correlation methods

Abstract

We have re-optimized the coefficients for ten scaling all correlation (SAC) methods, five empirical infinite basis (EIB) methods, and 18 multi-coefficient (MC) correlation methods, including the special cases of multi-coefficient SAC and multi-coefficient Gaussian-2 and Gaussian-3. The new parameterization is based on a training set of 82 atomization energies except for multi-coefficient Gaussian-2, which is restricted to H and the first period (nuclear charge ( 9) and is based on a training set of 52 atomization energies. Each method may be employed with or without including core-correlation effects, which are based on a new set of parameters optimized on a 125-molecule training set. The mean unsigned error in the atomization energies of the 82-molecule set is reduced on average by 20% when the new parameters used here are adopted.