ABINITIO PREDICTION OF THE GEOMETRY, VIBRATION PROPERTIES, POLARIZABILITIES, AND 1ST HYPERPOLARIZABILITIES OF PHOSPHAETHYNE

Results of ab initio calculations are presented, using the GAUSSIAN86 code, on the geometry, harmonic vibration frequencies vibration intensities, the dipole moment, the dipole polarizability tensors, and the first hyperpolarizability tensors for phosphaethyne. It is shown that if a large enough basis set is used, satisfactory results are obtained for the geometry and frequencies by including electron correlation at the MP2 level. However, with a double-ζ quality (DZ2P) basis better results for the geometry and frequencies are obtained by using the CCD or CISD methods. Multiple sets of polarization functions are shown to be necessary to get accurate values of the dipole moment and the polarizabilities. In particular, it is shown that whereas two carefully chosen sets of D polarization functions can give reasonable results for the dipole polarizability tensors, this is not the case for the first hyperpolarizability tensors. The latter require a set of more than four sets of diffuse D functions before stable results are obtained. © 1990 American Chemical Society.