Ab initio structures and quartic force fields of phosphine oxide and phosphine sulphide

Abstract

Phosphine oxide, OPH₃, and phosphine sulphide, SPH₃ have been studied ab initio using various combinations of theoretical methods (MP2, CCSD, CCSD(T)) and basis sets (cc-pV(X + d)Z, cc-pCVXZ, X = T,Q). For both molecules, high-level ab initio full-quartic force fields have been calculated, and these have been used to predict the most important spectroscopic constants for several isotopologues. For OPH₃, the semi-experimental equilibrium geometry and harmonic frequencies have been determined, by combining the theoretically calculated anharmonic corrections to the experimentally determined ground-state rotational constants and vibrational fundamentals. It is proved that, after applying anharmonic corrections, the unusually large disagreement between the experimental geometry and any high-level theoretical approach disappears.

Keywords:

• ab initio computations
• spectroscopic parameters
• anharmonic force field
• anharmonic corrections
• semi-experimental equilibrium structure

Acknowledgements

This work was supported by the University of Bologna, Polo di Rimini.