Scott Thais R, Hermes Matthew R, Sand Andrew M, Oakley Meagan S, Truhlar Donald G, Gagliardi Laura
Department of Chemistry, Chemical Theory Center, and Minnesota Supercomputing Institute, University of Minnesota, Minneapolis, Minnesota 55455, USA.
Department of Chemistry and Biochemistry, Butler University, Indianapolis, Indiana 46208, USA.
J Chem Phys. 2020 Jul 7;153(1):014106. doi: 10.1063/5.0007040.
Analytic gradients are important for efficient calculations of stationary points on potential energy surfaces, for interpreting spectroscopic observations, and for efficient direct dynamics simulations. For excited electronic states, as are involved in UV-Vis spectroscopy and photochemistry, analytic gradients are readily available and often affordable for calculations using a state-averaged complete active space self-consistent-field (SA-CASSCF) wave function. However, in most cases, a post-SA-CASSCF step is necessary for quantitative accuracy, and such calculations are often too expensive if carried out by perturbation theory or configuration interaction. In this work, we present the analytic gradients for multiconfiguration pair-density functional theory based on SA-CASSCF wave functions, which is a more affordable alternative. A test set of molecules has been studied with this method, and the stationary geometries and energetics are compared to values in the literature as obtained by other methods. Excited-state geometries computed with state-averaged pair-density functional theory have similar accuracy to those from complete active space perturbation theory at the second-order.
解析梯度对于高效计算势能面上的驻点、解释光谱观测结果以及进行高效的直接动力学模拟非常重要。对于涉及紫外可见光谱和光化学的激发电子态，使用状态平均完全活性空间自洽场（SA-CASSCF）波函数进行计算时，解析梯度很容易获得且通常成本较低。然而，在大多数情况下，为了获得定量精度，需要进行SA-CASSCF后的步骤，而如果通过微扰理论或组态相互作用来进行此类计算，往往成本过高。在这项工作中，我们基于SA-CASSCF波函数给出了多组态对密度泛函理论的解析梯度，这是一种成本更低的替代方法。我们用这种方法研究了一组测试分子，并将其驻点几何结构和能量与文献中通过其他方法获得的值进行了比较。用状态平均对密度泛函理论计算的激发态几何结构与二阶完全活性空间微扰理论计算的结果具有相似的精度。
