发表机构
University of Warsaw; Radboud University; Université Paul Sabatier; Nicolaus Copernicus University（华沙大学; 拉德堡德大学; 保罗·萨巴蒂尔大学; 尼古拉·哥白尼大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本文提出一阶简并对称性自适应微扰理论（dSAPT），用于量化简并电子态混合，通过静电和交换贡献分析，并验证了其在多个模型系统中的有效性。
AI 中文摘要
简并电子态控制着激基缔合物的光物理性质以及圆锥交叉附近的分子动力学。在势能面简并或近简并的区域，分子间相互作用会混合相应的电子构型。我们引入了一种具有弱对称性强制的对称性自适应微扰理论的一阶简并形式（dSAPT），该形式以静电和交换（泡利排斥）贡献来量化这种混合。我们比较了两种解决简并的替代方法，其中反对称性分别在一阶本征问题对角化之后或之前强制执行。使用CASSCF单体波函数，我们将dSAPT应用于两个模型空间简并系统，H$_2$--F(${}^2P$)和H$_2$--NO(${}^2\Pi$)，并表明在中间分子间距离下，交换效应已经对构型混合有显著贡献。对于H$_2$--NO(${}^2\Pi$)复合物，我们进一步证明，二阶色散能对于定性再现非绝热混合角的角依赖性至关重要。最后，使用水和苯的激基缔合物，其中单体由CASSCF或CIS波函数描述，我们表明泡利排斥在短分子间距离下控制着激发的离域化。
英文摘要
Degenerate electronic states govern the photophysics of excimers and the molecular dynamics near conical intersections. In regions where potential energy surfaces are degenerate or nearly degenerate, intermolecular interactions mix the corresponding electronic configurations. We introduce a first-order degenerate formulation of symmetry-adapted perturbation theory (dSAPT) with weak symmetry forcing that quantifies the mixing in terms of electrostatic and exchange (Pauli repulsion) contributions. We compare two alternative ways of resolving the degeneracy, in which antisymmetry is enforced either after or before diagonalization of the first-order eigenproblem. Using CASSCF monomer wave functions, we apply dSAPT to two model spatially degenerate systems, H$_2$--F(${}^2P$) and H$_2$--NO(${}^2Π$), and show that exchange effects contribute significantly to configuration mixing already at intermediate intermolecular separations. For the H$_2$--NO(${}^2Π$) complex, we further demonstrate that second-order dispersion energy is essential for qualitatively reproducing the angular dependence of the diabatic mixing angle. Finally, using water and benzene excimers with monomers described either by CASSCF or CIS wave functions, we show that Pauli repulsion controls delocalization of the excitation at short intermolecular separations.
