Self-consistent molecular orbital methods. XX. A basis set for correlated wave functions

A contracted Gaussian basis set (6-311G**) is developed by optimizing exponents and coefficients at the Møller-Plesset (MP) second-order level for the ground states of first-row atoms. This has a triple split in the valence s and p shells together with a single set of uncontracted polarization functions on each atom. The basis is tested by computing structures and energies for some simple molecules at various levels of MP theory and comparing with experiment.