Structures, vibrational frequencies, and electron affinities of SF₅O_n/SF₅O_n^- (n = 1-3)

The molecular structures, vibrational frequencies, and electron affinities of the SF₅O_n/SF₅O_n^- (n = 1-3) species have been examined with four hybrid density functional theory (DFT) methods. The basis set used in this work is of double-ζ plus polarization quality with additional diffuse s- and p-type functions, denoted DZP++. The geometries are fully optimized with each DFT method independently. The SF₅O_n (n = 1-3) species should be potential greenhouse gases. The anion SF₅O₂^- with C_s symmetry has a ³A″ electronic state, and the neutral SF₅O₃ with ²A″ electronic state has C_s symmetry. The anions SF₅O₂^- and SF₅O₃^- should be regarded as SF₅^-·O₂ and SF₅O^-·O₂ complexes, respectively. Three different types of the neutral-anion energy separation presented in this work are the adiabatic electron affinity (EA_ad), the vertical electron affinity (EA_vert), and the vertical detachment energy (VDE). The EA_ad values predicted by the B3PW91 method are 5.22 (SF₅O), 4.38 (SF₅O₂), and 3.61 eV (SF₅O₃). Compared with the experimental vibrational frequencies, the BHLYP method overestimates the frequencies, and the other three methods underestimate the frequencies. The bond dissociation energies D_e (SF₅O_n → SF₅O_n-m + O_m) for the neutrals SF₅O_n and D_e (SF₅O_n^- → SF₅O_n-m^- + O_m and SF₅O_n^- → SF₅O_n-m + O_m^-) for the anions SF₅O_n^- are reported.