Xu Xi, Yang Yang
Department of Chemistry and Theoretical Chemistry Institute, University of Wisconsin-Madison, 1101 University Avenue, Madison, Wisconsin 53706, USA.
J Chem Phys. 2020 Feb 28;152(8):084107. doi: 10.1063/1.5143371.
The nuclear-electronic orbital (NEO) framework enables the incorporation of nuclear quantum effects by treating both electrons and specific key nuclei quantum-mechanically. The conventional NEO method predicates on the controversial Born-Oppenheimer separation between classical and quantum nuclei, and its potential energy surface only depends on the coordinates of classical nuclei. In this paper, based on the fact that quantum nuclei are relatively localized, we develop the constrained nuclear-electronic orbital density functional theory (cNEO-DFT) by imposing a constraint on the expectation value of the quantum nuclear position. In this way, an extended NEO energy surface is obtained, which also depends on the quantum nuclear position. Compared to the potential energy surface obtained from conventional DFT, the extended NEO energy surface incorporates the nuclear quantum effects, which have notable impacts on the energy profile. Furthermore, cNEO-DFT can facilitate the location of NEO stationary states. It potentially can be used in geometry optimization, transition states search, and the calculation of reaction dynamics.
核电子轨道（NEO）框架通过对电子和特定关键原子核进行量子力学处理，能够纳入核量子效应。传统的NEO方法基于经典原子核与量子原子核之间存在争议的玻恩 - 奥本海默分离，其势能面仅取决于经典原子核的坐标。在本文中，基于量子原子核相对局域化这一事实，我们通过对量子核位置的期望值施加约束，发展了约束核电子轨道密度泛函理论（cNEO-DFT）。通过这种方式，获得了一个扩展的NEO能量面，它也取决于量子核位置。与从传统密度泛函理论（DFT）获得的势能面相比，扩展的NEO能量面纳入了核量子效应，这对能量分布有显著影响。此外，cNEO-DFT有助于确定NEO稳态的位置。它有可能用于几何优化、过渡态搜索以及反应动力学的计算。
