THE ANHARMONIC-FORCE FIELDS OF PH3, PHF2, PF3, PH5, AND H3PO

The cubic and quartic force fields of the title compounds are determined from ab initio SCF calculations using 6-31G** and TZP TZ2P basis sets. The computed geometries, vibration-rotation interaction constants, l-doubling constants, anharmonicity constants, and vibrational wavenumbers are compared with the available experimental data, especially for PH3 and PF3. Many experimentally unknown spectroscopic constants are predicted. A scaling procedure based on calculated harmonic and anharmonic force fields is proposed for predicting the vibrational wavenumbers of unknown molecules such as PH5. © 1990.