Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, USA.
J Chem Phys. 2012 Apr 14;136(14):144104. doi: 10.1063/1.3700802.
We have recently suggested the CC(P;Q) methodology that can correct energies obtained in the active-space coupled-cluster (CC) or equation-of-motion (EOM) CC calculations, which recover much of the nondynamical and some dynamical electron correlation effects, for the higher-order, mostly dynamical, correlations missing in the active-space CC/EOMCC considerations. It is shown that one can greatly improve the description of biradical transition states, both in terms of the resulting energy barriers and total energies, by combining the CC approach with singles, doubles, and active-space triples, termed CCSDt, with the CC(P;Q)-style correction due to missing triple excitations defining the CC(t;3) approximation.
我们最近提出了 CC(P;Q) 方法，该方法可以修正在活性空间耦合簇 (CC) 或运动方程 CC (EOMCC) 计算中获得的能量，这些能量可以恢复大部分活性空间 CC/EOMCC 考虑中缺失的非动力学和一些动力学电子相关效应。结果表明，通过将 CC 方法与单重态、双重态和活性空间三重态相结合，即 CCSDt，并采用由于缺失三重激发而定义 CC(t;3)近似的 CC(P;Q)风格校正，可以大大提高双自由基过渡态的描述，无论是在能量势垒还是总能量方面。
