SiN自由基X2∑+, A2Π和B2∑+ 电子态的光谱常数研究

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X²∑⁺, A²Π 和B²∑⁺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. 本文的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(T_e, R_e, ω_e, ω_ex_e, α_e和B_e), 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.     

SiN自由基X2∑+,A2∏和B2∑+电子态的光谱常数研究

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X2∑+,A2∏-和B2∑+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.     

SO自由基X3∑-, a1△和A''3△电子态的光谱常数

采用内收缩多参考组态相互作用(MRCI)方法计算了SO自由基X³∑^-, a¹△和A^'3△电子态的势能曲线. 采用Davidson修正避免由于MRCI方法本身的大小一致性缺陷产生的误差. 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-pCVDZ基组水平进行的. 为了提高计算精度,利用两点能量外推法,将各能量外推至完全极限处,得到外推后的势能曲线,再对势能曲线进行拟合,得到各种水平下三个电子态的光谱常     

Investigations of spectroscopic parameters and molecular constants for X1Σg+, w3Δu, and W1Δu electronic states of P2 molecule

The potential energy curves (PECs) of three low-lying electronic states (X¹Σ_g⁺, w³Δ_u, and W¹Δ_u)of P₂ molecule are investigated using the full valence complete active space self-consistent field (CASSCF) method followed by the highly accurate valence internally contracted multireference configuration interaction (MRCI) approach in conjunction with the correlation-consistent basis set in the valence range. The PECs of the electronic states involved are modified by the Davidson correction and extrapolated to the complete basis set (CBS) limit. With these PECs, the spectroscopic parameters of the three electronic states are determined and compared in detail with the experimental data. The comparison shows that excellent agreement exists between the present results and the available experimental data. The complete vibrational states are computed for the w³Δ_u, and W¹Δ_u electronic states when the rotational quantum number J equals zero and the vibrational level G(v), the inertial rotation constant B_v, and the centrifugal distortion constant D_v of the first 30 vibrational states are reported, which accord well with the experimental data. The present results show that the two-point extrapolation scheme can obviously improve the quality of spectroscopic parameters and molecular constants.     

Investigations of spectroscopic parameters and molecular constants for X1Σg+, w3△u, and W1△u electronic states of P2 molecule

The potential energy curves （PECs） of three low-lying electronic states （X～1Σ_g～+,w～3△u,and W～1△u） of P₂ molecule are investigated using the full valence complete active space self-consistent field （CASSCF） method followed by the highly accurate valence internally contracted multireference configuration interaction （MRCI） approach in conjunction with the correlation-consistent basis set in the valence range.The PECs of the electronic states involved are modified by the Davidson correction and extrapolated to the complete basis set （CBS） limit.With these PECs,the spectroscopic parameters of the three electronic states are determined and compared in detail with the experimental data.The comparison shows that excellent agreement exists between the present results and the available experimental data.The complete vibrational states are computed for the w～3△u and W～1△u electronic states when the rotational quantum number J equals zero and the vibrational level G（v）,the inertial rotation constant Bv,and the centrifugal distortion constant Dv of the first 30 vibrational states are reported,which accord well with the experimental data.The present results show that the two-point extrapolation scheme can obviously improve the quality of spectroscopic parameters and molecular constants.