论文标题
核电子轨道耦合簇方法中的三元电子 - 普罗替子激发和二阶近似
Triple electron-electron-proton excitations and second-order approximations in nuclear-electronic orbital coupled cluster methods
论文作者
论文摘要
核量子效应的准确描述（例如零点能量）对于建模广泛的化学和生物过程很重要。在核电子轨道（NEO）方法中，通过处理电子和选择核（通常是质子）用分子轨道技术机械地量子来以计算有效的方式纳入此类效应。在此，我们实现并测试了一种新耦合群集方法，该方法明确包括三重电子蛋白激发，其中两个电子和一个质子同时激发。我们的计算表明，这种NEO-CCSD（EEP）方法提供了高度准确的质子密度和质子亲和力，表现优于任何先前研究的NEO方法。这些示例强调了三元电子 - 普罗替子激发的重要性，以准确描述核量子效应。此外，我们还使用单打和双打（NEO-CC2）方法及其缩放 - 宽松自旋（SOS）版本实现并测试二阶近似耦合群集。 Neo-Sos $'$ -CC2方法，它缩放了电子 - 普罗顿相关能以及电子电子相关能的相对自旋和相同的旋转组件，其精度与所研究的属性的NEO-CCSD（EEP）方法几乎相同。由于其计算成本较低，该方法将为大分子系统提供广泛的化学和光化学应用。这项工作为NEO框架内的各种开发和应用奠定了基础。
The accurate description of nuclear quantum effects, such as zero-point energy, is important for modeling a wide range of chemical and biological processes. Within the nuclear-electronic orbital (NEO) approach, such effects are incorporated in a computationally efficient way by treating electrons and select nuclei, typically protons, quantum mechanically with molecular orbital techniques. Herein, we implement and test a NEO coupled cluster method that explicitly includes the triple electron-proton excitations, where two electrons and one proton are excited simultaneously. Our calculations show that this NEO-CCSD(eep) method provides highly accurate proton densities and proton affinities, outperforming any previously studied NEO method. These examples highlight the importance of the triple electron-electron-proton excitations for an accurate description of nuclear quantum effects. Additionally, we also implement and test the second-order approximate coupled cluster with singles and doubles (NEO-CC2) method, as well as its scaled-opposite-spin (SOS) versions. The NEO-SOS$'$-CC2 method, which scales the electron-proton correlation energy as well as the opposite-spin and same-spin components of the electron-electron correlation energy, achieves nearly the same accuracy as the NEO-CCSD(eep) method for the properties studied. Because of its low computational cost, this method will enable a wide range of chemical and photochemical applications for large molecular systems. This work sets the stage for a wide range of developments and applications within the NEO framework.
