The particle–particle random phase approximation (ppRPA) within the hole–hole channel was recently proposed as an efficient tool for computing excitation energies of point defects in solids [J. Phys. Chem. Lett. 2024, 15, 2757–2764]. In this work, we investigate the application of ppRPA within the particle–particle channel for predicting correlated excited states of point defects, including the carbon-vacancy (VC) in diamond, the oxygen-vacancy (VO) in magnesium oxide (MgO), and the carbon dimer defect (C_BC_N) in two-dimensional hexagonal boron nitride (h-BN). Starting from a density functional theory calculation of the (N – 2)-electron ground state, vertical excitation energies of the N-electron system are obtained as the differences between the two-electron addition energies. We show that active-space ppRPA with the B3LYP functional yields accurate excitation energies, with errors mostly smaller than 0.1 eV for tested systems compared to available experimental values. We further develop a natural transition orbital scheme within ppRPA, which provides insights into the multireference character of defect states. This study, together with our previous work, establishes ppRPA as a low-cost and accurate method for investigating excited-state properties of point defect systems.

中文翻译：

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用于预测点缺陷相关激发态的粒子-粒子随机相位近似


最近提出了孔-孔通道内的粒子-粒子随机相位近似（ppRPA）作为计算固体中点缺陷激发能的有效工具[ J. Phys。化学。莱特。 2024, 15, 2757–2764]。在这项工作中，我们研究了 ppRPA 在粒子-粒子通道中的应用，用于预测点缺陷的相关激发态，包括金刚石中的碳空位 (VC)、氧化镁 (MgO) 中的氧空位 (VO)、以及二维六方氮化硼（h-BN）中的碳二聚体缺陷（C _B C _N ）。从( N -2)电子基态的密度泛函理论计算出发，获得N电子体系的垂直激发能作为两个电子加合能之间的差值。我们表明，具有 B3LYP 函数的主动空间 ppRPA 可以产生准确的激发能量，与可用的实验值相比，测试系统的误差大多小于 0.1 eV。我们进一步在 ppRPA 内开发了一种自然过渡轨道方案，它提供了对缺陷态的多参考特征的见解。这项研究与我们之前的工作一起，将 ppRPA 确立为一种低成本且准确的方法，用于研究点缺陷系统的激发态特性。