支持一氧化钒（VO）旋振电子光谱计算精确建模的从头计算
Ab initio calculations to support accurate modelling of the rovibronic spectroscopy calculations of vanadium monoxide (VO)
摘要：
准确了解一氧化钒（VO）的旋振近红外和可见光谱对于研究冷恒星和热行星大气具有重要意义。在这里，所需的从头计算偶极矩和自旋轨道耦合曲线VO。这些数据构成了新VO行列表的基础，该列表考虑了13种不同的电子状态，包含超过2.77亿次转换。开壳层过渡金属化合物由于其大量的低电子态、显著的自旋轨道耦合以及强的静态和动态电子关联，是具有挑战性的从头计算量子力学模型。多参考组态相互作用方法使用轨道从一个完整的积极空间自洽场（CASSCF）的计算是这些系统的标准技术。我们使用不同的状态特定或最小状态CASSCF轨道为每个电子状态，以最大限度地提高计算精度。非对角偶极矩控制电子跃迁的强度。我们测试了有限场非对角偶极矩，但发现（1）激发能的准确性不足以评估准确的偶极矩，（2）垂直跃迁的计算机时间要求过高。最好的非对角偶极矩计算使用不同的CASSCF轨道的波函数。
英文摘要：
Accurate knowledge of the rovibronic near-infrared and visible spectra of vanadium monoxide (VO) is very important for studies of cool stellar and hot planetary atmospheres. Here, the required ab initio dipole moment and spin-orbit coupling curves for VO are produced. This data forms the basis of a new VO line list considering 13 different electronic states and containing over 277 million transitions. Open shell transition, metal diatomics are challenging species to model through ab initio quantum mechanics due to the large number of low-lying electronic states, significant spin-orbit coupling and strong static and dynamic electron correlation. Multi-reference configuration interaction methodologies using orbitals from a complete active space self-consistent-field (CASSCF) calculation are the standard technique for these systems. We use different state-specific or minimal-state CASSCF orbitals for each electronic state to maximise the calculation accuracy. The off-diagonal dipole moment controls the intensity of electronic transitions. We test finite-field off-diagonal dipole moments, but found that (1) the accuracy of the excitation energies were not sufficient to allow accurate dipole moments to be evaluated and (2) computer time requirements for perpendicular transitions were prohibitive. The best off-diagonal dipole moments are calculated using wavefunctions with different CASSCF orbitals.
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