A study on spectroscopic parameters of X2Σ+, A2Π and B2Σ+ low-lying electronic states of SiN radical

The potential energy curves (PECs) of X-2 Sigma(+), A(2)Pi and B-2 Sigma(+) low-lying electronic states of SiN radical are investigated using the highly accurate valence internally contracted multireference configuration interaction (MRCI) approach combining the full valence complete active space self-consistent field method. In the present calculations, the basis sets used are correlation-consistent basis sets, aug-cc-pV6Z. The PECs determined by the MRCI calculations are corrected for size-extensivity errors by means of the Davidson modification (MRCI +Q). To obtain more reliable results, effects of the core-valence correlation and relativistic correction on the PEC are taken into account. The core-valence correlation correction is carried out with the cc-pCV5Z basis set. The way to consider the relativistic correction is to use the second-order Douglas-Kroll Hamiltonian approximation, and the correction is performed at the level of cc-pV5Z basis set. With these PECs, the spectroscopic parameters are determined. A comparison with the experimental data shows that the present spectroscopic parameters are more accurate than the previous calculations.