Population Analysis with Hydrogen 2 p Polarization Functions

The importance of including polarization functions in the basis set of ab initio MO calculations has received a good deal of attention during the last few years [1—8]. However, little work has been reported on the influence of the inclusion of polarization functions in the basis set of semiempirical methods. The only papers dealing with semiempirical methods that the authors are aware of are, on the one hand, those [9—12] in which polarization functions are included in the CNDO/2 [13] basis set to calculate electrical polarizabilities, and, on the orther hand, their own previous work [14] where hydrogen 2p polarization functions were included in the INDO [13] basis set in order to study their influence on the Fermi contact term of spin-spin coupling constants. In the present paper the same INDO version of the previous work [14] has been used to perform population analysis in a set of molecules containing hydrogen as well as some of the first row atoms carbon, oxygen, nitrogen and/or fluorine.