SINGLET-STATE AND TRIPLET-STATE NI(C2H4) - A DENSITY-FUNCTIONAL STUDY

Fully optimized geometries, harmonic frequencies, infrared intensities , and bond dissociation energies obtained from local and nonlocal dens ity functional calculations are presented for the ground-state (1A1) a nd a triplet excited-state Ni(C2H4). The ground-state complex has a C2 v equilibrium structure, whereas the symmetry is lowered to C(s) for t he triplet state. The best estimation of the binding energy of the gro und state is 38.9 kcal/mol, which is about 4 kcal/mol higher than the experimental value. The nickel-ethylene bond is much weaker in the tri plet complex; the binding energy is estimated to be about 9 kcal/mol. The comparison of the theoretical infrared spectra, the shifts in the CC stretch, and CH2 scissor frequencies upon coordination and the H/D isotopic shifts with those from a recent matrix-isolation IR study sho ws a remarkable agreement for the groundstate Ni(C2H4). The effect of the nonlocal corrections to the exchange-correlation energy is discuss ed for each calculated property.