A theoretical study on the equilibrium structures, vibrational frequencies and photoelectron spectroscopy of thiocarbonyl fluoride by using density functional and coupled-cluster theories

摘要

The equilibrium geometries, vibrational frequencies and normal modes of F_2CS and F_2CS~+ X~2B_2, A~2B_1 and B~2A_1 states were obtained by utilizing both density functional and coupled-cluster (CC2) theories. Franck-Condon factors were calculated by using the harmonic-oscillator model taking into account the Duschinsky effect, based on which photoelectron spectra were simulated. The adiabatic ionization energies were computed by the CCSD(T) method extrapolated to the complete basis set limit. The computed equilibrium structures and vibrational frequencies are generally in agreement with the experiment, except in few cases. The B3LYP and CC2 approaches perform equally well in the computations of F_2CS. The simulated photoelectron spectra of F_2CS are also in accord with the experiment, indicating that the calculated structures are reliable. The computed adiabatic ionization energies are in agreement with the experiment within 0.01, 0.02, and 0.06 eV for the three ionic states, respectively.