Self-Consistent Molecular Orbital Methods. XIV. An Extended Gaussian-Type Basis for Molecular Orbital Studies of Organic Molecules. Inclusion of Second Row Elements

We have recently proposed an extended basis of atomic functions expressed as fixed linear combinations of Gaussian functions for hydrogen and the first row atoms Ditchfield, Hehre, and Pople, J. Chem. Phys. 54, 724 (1971); Hehre and Pople, J. Chem. Phys., 56, 4233 (1972). We now extend our treatment to consider atoms of the second row. This basis set is close to minimal in that each inner shell atomic orbital is represented by a single function and only valence shell orbitals (3s, 3p) are extended, these being split into inner and outer parts. No functions of higher quantum number than are necessary in the ground state atom are included. We have considered the effect of molecular environment on the size of the valence shell orbitals and have proposed a ``standard set'' of scaling factors.