Structures, thermochemistry and electron affinities of the selenium hydrides SeH_n/SeH_n^-(n=1-5)

Seven different density functional theory (DFT) methods were employed to predict the molecular structures, electron affinities, and first dissociation energies of the SeH_n/SeH_n^- (n=1-5) molecules. The three type of electron affinities reported in this work are the adiabatic electron affinity (E_Aad), the vertical electron affinity (E_Avert), and the vertical detachment energy (VDE). The basis set used is of double-ζ plus polarization quality with additional s- and p-type diffuse functions, labeled as DZP++. The ground states of SeH/SeH^-, SeH₂/SeH₂^-, SeH₃/SeH₃^-, SeH₄/SeH₄^- and SeH₅/SeH₅^- are C_∝v/C_∝v, C_2v (²A₁)/C_s(²A′), C_s(²A₁)/C_2v (¹A₁), C_2v(¹A₁)/C_4v (²A₁), C_4v(²A₁)/C_4v (¹A₁), respectively. Compared with the experimental values, the B3P86 and B3PW91 methods give good results for the molecular structures, the BLYP method in all of these schemes is the best in respect of predicting electron affinities, the BP86 method determines the vibrational frequencies in best agreement with experimental data, meanwhile, the BHLYP methods gives good results for the first dissociation energies.