THEORETICAL MOLECULAR-STRUCTURES AND VIBRATIONAL FREQUENCIES FOR THE DIOXODIHALIDES OF CHROMIUM(VI) AND MOLYBDENUM(VI)

Density functional theory calculations are reported for the ground-state geometries and harmonic vibrational energies of MO2X2 (M = Cr, Mo; X = F, CI). Both local density approximation (LDA) and nonlocal generalized gradient approximation (GGA) functionals were investigated using several different STO basis sets. Both LDA and GGA results using basis sets of double-zeta plus polarization function quality yield bond lengths and angles within about 0.02 angstrom and 3-degrees of experiment. GGA vibrational energies are systematically predicted to be lower than observed but only by about 5% and 8% for the Cr and Mo species, respectively. The implications of these results for the complete ab initio estimation of zero point energies together with thermodynamic quantities at experimentally accessible temperatures are discussed.