Theoretical characterization of the LiSH potential energy surface

Abstract

Electronic structure calculations have been performed to characterize the potential energy surface of the LiSH. For such, molecular properties have been calculated using two different levels of theories: DFT/B3LYP and CASSCF. As results, the obtained equilibrium geometry at CAS(8,13)/VQZ level of theory is R_Li-S = 4.0975 a₀, R_S-H = 2.5502 a₀, and θ = 93.37°. The present vibrational harmonic frequencies are in good agreement with those previously reported in the literature. Our results show the overall endothermicity of the Li(²P) + SH(X²Π) → H(²S) + LiS(X²Π) to be about 0.508 eV without ZPE corrections at CAS(8,13)/VQZ. Besides, the role of the molecular singlet-triplet transitions, essential for the interpretation of the phosphorescence spectra, is discussed. Overall, the present findings reproduced well the experimental ones and, therefore, can be used as a benchmark for other theoretical and experimental studies.