标题： 基于pCCD方法计算轨道能量和成对轨道能量的简单高效计算策略 显示英文标题

标题： Simple and efficient computational strategies for calculating orbital energies and pair-orbital energies from pCCD-based methods

摘要： 我们引入了经济的计算策略，用于计算原子和分子系统中的轨道和成对轨道能量。 我们的方法基于成对耦合簇双激发（pCCD）假设及其轨道优化变体。 然后，计算得到的轨道和成对轨道能量被用来近似电离势（IP）、电子亲和力（EA）、由此产生的电荷间隙、双电离势（DIP）和双电子亲和力（DEA）。 我们的方法建立在标准的库普曼定理基础上，并将其扩展到基于pCCD的波函数。 此外，我们利用规范哈特里-福克轨道或自然pCCD优化轨道，将pCCD电子相关效应纳入模型中。 后者代表了（D）IP/D（EA）运动方程pCCD模型的对角近似。 我们针对各种基组大小下的选定原子以及一组24种有机受体分子的理论和可用实验数据对新开发的模型进行了基准测试。 我们的数值结果表明，基于pCCD自然轨道的库普曼方法对占据轨道和虚拟轨道能量提供了平衡处理，从而以较低的计算成本实现了电荷间隙的可靠预测。 显示英文摘要

摘要： We introduce affordable computational strategies for calculating orbital and pair-orbital energies in atomic and molecular systems. Our methods are based on the pair Coupled Cluster Doubles (pCCD) ansatz and its orbital-optimized variant. The computed orbital and pair-orbital energies are then subsequently used to approximate ionization potentials (IP), electron affinities (EA), the resulting charge gaps, double ionization potentials (DIP), and double electron affinities (DEA). Our methodology builds on the standard Koopmans' theorem and extends it for a pCCD-based wave function. Furthermore, we incorporate pCCD electron correlation effects into the model utilizing canonical Hartree-Fock or natural pCCD-optimized orbitals. The latter represents a diagonal approximation to the (D)IP/D(EA) equation of motion pCCD models. We benchmarked our newly developed models against theoretical and available experimental data for selected atoms in various basis set sizes and a set of 24 organic acceptor molecules. Our numerical results show that the Koopmans' approach based on pCCD natural orbitals provides a balanced treatment of occupied and virtual orbital energies, resulting in reliable predictions of charge gaps at a low computational cost.