Density functional study of the vibrational spectra of octahedral transition-metal hexacarbonyls: Neutral molecules (M = Cr, Mo, W) and isoelectronic ions (M = V, Nb, Ta; Mn, Re; Fe, Ru, Os; Co, Rh, Ir; Pt; Au)

The geometries, harmonic force fields, and charge distributions of the title compounds have been calculated at the level of gradient-corrected density functional theory (DFT) using effective core potential wave functions in conjunction with polarized double-and triple-zeta basis sets. The DFT results are in very good agreement with the available experimental data for both the neutral and ionic systems. Theoretical predictions are made for highly charged hexacarbonyl cations that are as yet unknown (M = Co, Rh, Pt, Au) to facilitate their spectroscopic detection. Trends in the computational results are discussed in terms of bonding models and electrostatic effects, emphasizing the variation of the calculated properties with the total charge of the hexacarbonyls.