Explicitly correlated treatment of H_2NSi and H_2SiN radicals: Electronic structure calculations and rovibrational spectra

摘要

Various ab initio methods are used to compute the six dimensional potential energy surfaces (6D-PESs) of the ground states of the H_2NSi and H_2SiN radicals. They include standard coupled cluster (RCCSD(T)) techniques and the newly developed explicitly correlated RCCSD(T)-F12 methods. For H_2NSi, the explicitly correlated techniques are viewed to provide data as accurate as the standard coupled cluster techniques, whereas small differences are noticed for H_2SiN. These PESs are found to be very flat along the out-of-plane and some in-plane bending coordinates. Then, the analytic representations of these PESs are used to solve the nuclear motions by standard perturbation theory and variational calculations. For both isomers, a set of accurate spectroscopic parameters and the vibrational spectrum up to 4000 cm~(-1) are predicted. In particular, the analysis of our results shows the occurrence of anharmonic resonances for H_2SiN even at low energies.