The anharmonic force fields of HOF and F2O

Abstract

Ab initio predictions at the SCF, CISD, and CCSD levels are reported for the title compounds using DZP and TZP basis sets. The calculated geometries, rotational constants, dipole moments, fundamental frequencies, isotopic frequency shifts, vibration–rotation interaction constants, centrifugal distortion constants, Coriolis coupling constants, and infrared band intensities are compared with experimental data (if available). The best agreement is usually found for the CCSD results. The experimentally derived cubic force field of F₂O is reproduced well by our results so that the predicted cubic and quartic force fields of HOF and the predicted quartic force field of F₂O are also expected to be realistic. On the basis of our theoretical anharmonic constants, a new interpretation is suggested for the anomalous isotopic frequency shift of ν₃ in HOF and DOF. Finally, an experimentally derived r_e structure with R(O–F)=1.4356 Å, r(O–H)=0.9664 Å, and α(H–O–F)=97.72° is proposed for HOF on the basis of the TZP CCSD vibration–rotation interaction constants.