SiN自由基X^2Σ^+,A^2Π和B^2Σ^+电子态的光谱常数研究

A study on spectroscopic parameters of X^2Σ^+ , A^2Π and B^2Σ^+ low-lying electronic states of SiN radical

采用内收缩多参考组态相互作用(MRCI)方法,结合价态范围内的最大相关一致基aug-cc-pV6Z,计算了SiN自由基X2Σ+,A2Π和B2Σ+电子态的势能曲线.采用Davidson修正来避免由于MRCI方法本身的大小一致性缺陷产生的误差.为了提高计算精度,进一步考虑了相对论修正和核价相关修正对势能曲线的影响.相对论修正是利用二阶Douglas-Kroll哈密顿近似在cc-pV5Z基组水平进行的;同时核价相关修正是在cc-pCV5Z基组水平进行的.对这些势能曲线进行拟合,得到各种水平下三个电子态的光谱常数(Te,Re,ωe,ωexe,αe和Be),并详细分析了Davidson修正、相对论修正和核价相关修正对光谱常数的影响.与其他理论结果和实验数据进行比较,可知本文的结果更精确、更完整.

The potential energy curves （PECs） of X2∑＋, A2П and B2∑＋ 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 carded 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.