Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093, USA.
Department of Chemistry, University of California, Berkeley, California 94720, USA.
J Chem Phys. 2017 Oct 28;147(16):161715. doi: 10.1063/1.4993213.
This study presents the extension of the MB-nrg (Many-Body energy) theoretical/computational framework of transferable potential energy functions (PEFs) for molecular simulations of alkali metal ion-water systems. The MB-nrg PEFs are built upon the many-body expansion of the total energy and include the explicit treatment of one-body, two-body, and three-body interactions, with all higher-order contributions described by classical induction. This study focuses on the MB-nrg two-body terms describing the full-dimensional potential energy surfaces of the M(HO) dimers, where M = Li, Na, K, Rb, and Cs. The MB-nrg PEFs are derived entirely from "first principles" calculations carried out at the explicitly correlated coupled-cluster level including single, double, and perturbative triple excitations [CCSD(T)-F12b] for Li and Na and at the CCSD(T) level for K, Rb, and Cs. The accuracy of the MB-nrg PEFs is systematically assessed through an extensive analysis of interaction energies, structures, and harmonic frequencies for all five M(HO) dimers. In all cases, the MB-nrg PEFs are shown to be superior to both polarizable force fields and ab initio models based on density functional theory. As previously demonstrated for halide-water dimers, the MB-nrg PEFs achieve higher accuracy by correctly describing short-range quantum-mechanical effects associated with electron density overlap as well as long-range electrostatic many-body interactions.
本研究扩展了多体能量（MB-nrg）转移势能函数（PEF）理论/计算框架，用于碱金属离子-水体系的分子模拟。MB-nrg PEF 基于总能量的多体展开，包括对单、双和三体相互作用的显式处理，所有更高阶的贡献都由经典感应来描述。本研究侧重于描述 M(HO)二聚体全维势能表面的 MB-nrg 二体项，其中 M = Li、Na、K、Rb 和 Cs。MB-nrg PEF 完全由在显式相关耦合簇水平上进行的“第一性原理”计算得出，包括对 Li 和 Na 的单、双和微扰三重激发 [CCSD(T)-F12b]，以及对 K、Rb 和 Cs 的 CCSD(T)水平。通过对所有五个 M(HO)二聚体的相互作用能、结构和调和频率进行广泛分析，系统地评估了 MB-nrg PEF 的准确性。在所有情况下，MB-nrg PEF 都优于极化力场和基于密度泛函理论的从头算模型。正如先前对卤化物-水二聚体的研究表明的那样，MB-nrg PEF 通过正确描述与电子密度重叠相关的短程量子力学效应以及远程静电多体相互作用，实现了更高的准确性。
