Ab initio determination of the anharmonic vibrational spectra of P2O in the region 200-2000 cm(-1)

An ab initio quartic force held calculated from a cc-pVTZ basis set at CCSD (T) level of theory is used to compute the vibrational energy levels of dip hosphorus oxide, P2O, in the range 200-2000 cm(-1). The most important vibr ational configurations, constructed from harmonic vibrational wavefunctions , selected by an iterative process by means of a variational perturbational method are diagonalized. The results show a good agreement with the most r eliable experimental values such as upsilon (3), the upsilon (1) + upsilon (3) <-- <upsilon>(1) hot band and two postulated Fermi resonances and predi ct unobserved overtones and combinations bands in the medium IR region. (C) 2001 Elsevier Science B.V. All rights reserved.