Chibueze Chima S, Visscher Lucas
Department of Chemistry and Pharmaceutical Sciences, Vrije Universiteit, De Boelelaan 1108, 1081 HZ Amsterdam, The Netherlands.
J Chem Phys. 2024 Sep 7;161(9). doi: 10.1063/5.0226870.
When using quantum chemical methods to study electronically excited states of open-shell molecules, it is often beneficial to start with wave functions that are spin eigenfunctions. For excited states of molecules containing heavy elements, spin-orbit coupling (SOC) is important and needs to be included as well. An efficient approach is to include SOC perturbatively on top of a restricted open-shell Kohn-Sham (ROKS) time-dependent density functional theory, which can be combined with the Tamm-Dancoff approximation (TDA) to suppress numerical instabilities. We implemented and assessed the potential of such a ROKS-TDA-SOC method, also featuring the possibility of calculating transition dipole moments between states to allow for full spectrum simulation. Our study shows that the ROKS-TDA-SOC formalism yields a clear and easy-to-use method to obtain electronically excited states of open-shell molecules that are of moderate size and contain heavy elements.
在使用量子化学方法研究开壳层分子的电子激发态时，从自旋本征函数的波函数开始通常是有益的。对于含有重元素的分子的激发态，自旋轨道耦合（SOC）很重要，也需要考虑在内。一种有效的方法是在受限开壳层Kohn-Sham（ROKS）含时密度泛函理论的基础上微扰地包含SOC，该理论可以与Tamm-Dancoff近似（TDA）相结合以抑制数值不稳定性。我们实现并评估了这种ROKS-TDA-SOC方法的潜力，该方法还具有计算态间跃迁偶极矩以进行全光谱模拟的可能性。我们的研究表明，ROKS-TDA-SOC形式提供了一种清晰且易于使用的方法，用于获得中等大小且含有重元素的开壳层分子的电子激发态。
