Jr. Durig et Zn. Shen, VIBRATIONAL-SPECTRA AND STRUCTURE FROM AB-INITIO CALCULATIONS OF TETRAFLUORODIPHOSPHINE, Vibrational spectroscopy, 13(2), 1997, pp. 195-203
Ab initio calculations have been carried out for tetrafluorodiphosphin
e, P2F4, up to the MP2/6-311 + G level. The harmonic force constants
and vibrational frequencies along with infrared and Raman intensities
for the most stable trans conformer have been obtained from these calc
ulations which provide a basis for the vibrational assignment. Several
reassignments of the fundamentals from those previously given were re
quired from these data. The calculations indicate that the gauche conf
ormer should be a stable rotamer but more than 800 cm(-1) (2.3 kcal/mo
l) higher in energy which helps explain why this conformer has not bee
n observed in the vibrational spectrum of the sample at ambient temper
ature. The predicted P-F distances from the MP2/6-311 + G calculation
s are more than 0.031 Angstrom longer than the experimentally determin
ed values. The potential function governing conformer interchange and
the change in geometric parameters with internal rotation have been pr
edicted from the ab initio calculations. The results are compared to t
he corresponding results from similar molecules.