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首页> 外文期刊>The Journal of Chemical Physics >Active-space symmetry-adapted-cluster configuration-interaction and equation-of-motion coupled-cluster methods for high accuracy calculations of potential energy surfaces of radicals
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Active-space symmetry-adapted-cluster configuration-interaction and equation-of-motion coupled-cluster methods for high accuracy calculations of potential energy surfaces of radicals

机译：主动空间对称自适应簇构型相互作用和运动方程耦合簇方法，用于基团势能面的高精度计算

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The electron-attached (EA) and ionized (IP) symmetry-adapted-cluster configuration-interaction (SAC-CI) methods and their equation-of-motion coupled-cluster (EOMCC) analogs provide an elegant framework for studying open-shell systems.As shown in this study,these schemes require the presence of higher-order excitations,such as the four-particle-three-hole (4p-3h) or four-hole-three-particle (4h-3p) terms,in the electron attaching or ionizing operator R in order to produce accurate ground- and excited-state potential energy surfaces of radicals along bond breaking coordinates.The full inclusion of the 4p-3h/4h-3p excitations in the EA/IP SAC-CI and EOMCC methods leads to schemes which are far too expensive for calculations involving larger radicals and realistic basis sets.In order to reduce the large costs of such schemes without sacrificing accuracy,the active-space EA/IP EOMCC methodology [J.R.Gour et al,J.Chem.Phys.123,134113 (2005)] is extended to the EA/IP SAC-CI approaches with 4p-3h/4h-3p excitations.The resulting methods,which use a physically motivated set of active orbitals to pick out the most important 3p-2h/3h-2p and 4p-3h/4h-3p excitations,represent practical computational approaches for high-accuracy calculations of potential energy surfaces of radicals.To illustrate the potential offered by the active-space EA/IP SAC-CI approaches with up to 4p-3h/4h-3p excitations,the results of benchmark calculations for the potential energy surfaces of the low-lying doublet states of CH and OH are presented and compared with other SAC-CI and EOMCC methods,and full CI results.
机译：电子连接（EA）和离子化（IP）对称集群配置相互作用（SAC-CI）方法及其运动方程耦合集群（EOMCC）类似物为研究开放壳系统提供了一个优雅的框架如本研究所示，这些方案要求存在更高阶的激发，例如，四粒子三孔（4p-3h）或四孔三粒子（4h-3p）项。电子附着或电离算子R以便沿键断裂坐标生成自由基的准确基态和激发态势能面。EA / IP SAC-CI和EOMCC中完全包含4p-3h / 4h-3p激发方法导致方案对于包含较大根基和现实基集的计算而言过于昂贵。为了减少此类方案的巨额成本而又不牺牲准确性，主动空间EA / IP EOMCC方法论[JRGour等，J。 Chem.Phys.123,134113（2005）]扩展到4p的EA / IP SAC-CI方法-3h / 4h-3p激发。所得方法使用一组物理激励的主动轨道来挑选最重要的3p-2h / 3h-2p和4p-3h / 4h-3p激发，这些方法代表了实用的高强度计算方法。自由基的势能面的高精度计算。为说明有源空间EA / IP SAC-CI方法提供的势能，该方法具有最多4p-3h / 4h-3p激发，对势能面的基准计算结果介绍了低价的CH和OH的双峰态，并与其他SAC-CI和EOMCC方法进行了比较，并获得了完全CI结果。

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