The modeling of spin–orbit coupling (SOC) remains a challenge in computational chemistry due to the high computational cost. With the rising popularity of spin-driven processes and f-block metals in chemistry and materials science, it is incumbent on the community to develop accurate multiconfigurational SOC methods that scale to large systems and understand the limits of different treatments of SOC. Herein, we introduce an implementation of perturbative SOC in scalar-relativistic two-component CASSCF (srX2C-CASSCF-SO). Perspectives on the limitations and accuracy of srX2C-CASSCF-SO are presented via benchmark calculations.

中文翻译：

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二分量 CASSCF 内变分和微扰自旋轨道耦合的比较

由于计算成本较高，自旋轨道耦合（SOC）的建模仍然是计算化学中的一个挑战。随着自旋驱动过程和 f 区金属在化学和材料科学中的日益普及，社区有责任开发精确的多构型 SOC 方法，以扩展到大型系统并了解 SOC 不同处理的局限性。在这里，我们介绍了标量相对论二分量 CASSCF (srX2C-CASSCF-SO) 中微扰 SOC 的实现。通过基准计算提出了对 srX2C-CASSCF-SO 的局限性和准确性的看法。