The accurate description of ground- and excited-state potential energy surfaces poses a challenge for many electronic structure methods, especially in regions where strong electronic state interaction occurs. Here we introduce a new methodology, state-interaction pair-density functional theory (SI-PDFT), to target molecular systems exhibiting strong interaction of electronic states. SI-PDFT is an extension of multiconfiguration pair-density functional theory in which a set of N electronic states is generated through the diagonalization of an N × N effective Hamiltonian. We demonstrate the accuracy of the method by performing calculations on the ionic–neutral avoided crossing in lithium fluoride and the ¹ππ-¹πσ^* avoided crossing in the H—O bond photodissociation in phenol. We show that SI-PDFT can be a useful tool in the study of photochemistry and nonadiabatic dynamics.

中文翻译：

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状态相互作用对密度泛函理论

精确描述基态和激发态势能面对许多电子结构方法提出了挑战，尤其是在发生强烈电子态相互作用的区域。在这里，我们介绍了一种新的方法，即状态相互作用对密度泛函理论（SI-PDFT），以靶向表现出强电子态相互作用的分子系统。SI-PDFT是多配置对密度泛函理论的扩展，其中通过N × N有效哈密顿量的对角化生成一组N个电子态。我们通过在氟化锂离子中性避免交叉点和执行计算验证了该方法的准确度^1个ππ - ¹πσ ^*避免了酚中H-O键光解离的交叉。我们表明，SI-PDFT可以是光化学和非绝热动力学研究中的有用工具。