UGA-SSMRPT2 -- 一种多参考微扰理论，用于在多种分子系统中准确预测电子激发能级
UGA-SSMRPT2 -- A Multireference Perturbation Theory Predicting Accurate Electronic Excitation Energies in Diverse Molecular Systems
AI总结：
UGA-SSMRPT2 提出了一种多参考微扰理论，用于在多种分子系统中准确预测电子激发能级，具有高精度和计算效率。
摘要：
UGA-SSMRPT2 是 Mukerjee 的 State-Specific Multireference Coupled Cluster Theory（MkMRCC）的无自旋微扰类比，已知在构建解离曲线时能够实现尺寸扩展性和无入侵态的构造。本研究证明 UGA-SSMRPT2 也是一种准确且计算成本低的框架，用于计算激发能级。该方法在大多数 π→π*、n→π*、电荷转移、价瑞德伯和瑞德伯激发态中能够达到接近化学精度。我们的结果表明 UGA-SSMRPT2 的激发能级与 EOM-CCSD 和/或公认的理论最佳估计值相差在 0.20 eV 以内，通常优于 NEVPT2、CASPT2 和 MCQDPT 等流行方法，同时通常需要更小的活化空间。其状态特异性公式规避了已知的入侵态问题，并消除了 CASPT2 中需要的经验参数如 IPEA 移位。本研究将 UGA-SSMRPT2 提议为一种稳健且可扩展的方法，用于建模具有挑战性的电子激发态。
英文摘要：
UGA-SSMRPT2, the spin-free perturbative analogue of Mukerjee's State-Specific Multireference Coupled Cluster Theory (MkMRCC) is known to be successful for size-extensive and intruder-free construction of dissociation curves. This work demonstrates that UGA-SSMRPT2 is also an accurate and computationally inexpensive framework for computing excitation energies. The method achieves near-chemical accuracy for the vast majority of $π\to π^*$, $n \to π^*$, charge-transfer, valence-Rydberg and Rydberg excited states commonly used for benchmarking electronic structure theories for excited states. Our results demonstrate that UGA-SSMRPT2 excitation energies lie within 0.20 eV of EOM-CCSD and/or well-established theoretical best estimates often surpassing the popular MRPT2 approaches like NEVPT2, CASPT2, and MCQDPT while typically requiring smaller active spaces. Its state-specific formulation circumvents the well-known intruder-state problem and eliminates the need for empirical parameters such as IPEA shifts in CASPT2. This work proposes UGA-SSMRPT2 as a robust, and scalable approach for modeling challenging electronic excited states.
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