Valentine Andrew J S, Li Xiaosong
Department of Chemistry, University of Washington, Seattle, Washington 98195, USA.
J Chem Phys. 2019 Aug 28;151(8):084107. doi: 10.1063/1.5113815.
The change in electronic state from one spin multiplicity to another, known as intersystem crossing, occurs in molecules via the relativistic phenomenon of spin-orbit coupling. Current means of estimating intersystem crossing rates rely on the perturbative evaluation of spin-orbit coupling effects. This perturbative approach, valid in lighter atoms where spin-orbit coupling is weaker, is expected to break down for heavier elements where relativistic effects become dominant. Methods which incorporate spin-orbit effects variationally, such as the exact-two-component (X2C) method, will be necessary to treat this strong-coupling regime. We present a novel procedure which produces a diabatic basis of spin-pure electronic states coupled by spin-orbit terms, generated from fully variational relativistic calculations. This method is implemented within X2C using time-dependent density-functional theory and is compared to results from a perturbative relativistic study in the weak spin-orbit coupling regime. Additional calculations on a more strongly spin-orbit-coupled [UOCl] complex further illustrate the strengths of this method. This procedure will be valuable in the estimation of intersystem crossing rates within strongly spin-coupled species.
电子态从一种自旋多重性转变为另一种自旋多重性的过程，即所谓的系间窜越，在分子中通过自旋 - 轨道耦合的相对论现象发生。当前估计系间窜越速率的方法依赖于自旋 - 轨道耦合效应的微扰评估。这种微扰方法在自旋 - 轨道耦合较弱的轻原子中有效，但对于相对论效应占主导的重元素，预计会失效。对于这种强耦合体系，需要采用变分法纳入自旋 - 轨道效应的方法，例如精确二分量（X2C）方法来处理。我们提出了一种新颖的程序，该程序通过完全变分相对论计算生成由自旋 - 轨道项耦合的自旋纯电子态的 diabatic 基。该方法在 X2C 框架内使用含时密度泛函理论实现，并与弱自旋 - 轨道耦合区域的微扰相对论研究结果进行比较。对自旋 - 轨道耦合更强的[UOCl]配合物的额外计算进一步说明了该方法的优势。此程序在估计强自旋耦合物种中的系间窜越速率方面将具有重要价值。
