THE ALKALI-METAL TRIFLUORIDES M(-) - HOW WELL CAN THEORY PREDICT EXPERIMENT()F(3)()

The alkali metal trifluorides M(+)F(3)(-) (M = Na,K, Rb, and Ca) are s tudied using density functional theory and traditional ab initio metho ds. Experimental infrared and Raman spectroscopic results suggest a pr onounced change in the structure of the M(+)F(3)(-) species with decre asing cation size. Stationary points are located on the M(+)F(3)(-) po tential energy surfaces and harmonic vibrational frequencies computed to assess how well the various theoretical methods can describe this a lkali metal dependence. As with the isolated F-3(-) anion, the theoret ical results are strongly dependent on the method used, with only the B3-LYP density functional calculations reproducing correctly the struc tural variation inferred from the vibrational spectra. Additional calc ulations also demonstrate that this functional significantly reduces t he F-3(-) overbinding observed using B-LYP.