Simonson Thomas, Hummer Gerhard, Roux Benoît
Laboratoire de Biochimie (CNRS UMR7654), Ecole Polytechnique , 91128 Palaiseau, France.
Department of Theoretical Biophysics, Max Planck Institute of Biophysics , 60438 Frankfurt am Main, Germany.
J Phys Chem A. 2017 Feb 23;121(7):1525-1530. doi: 10.1021/acs.jpca.6b12691. Epub 2017 Feb 13.
Condensed-phase simulations commonly use periodic boundary conditions (PBCs) to represent the thermodynamic limit. For the vapor to liquid transfer of an ion, the gas/liquid boundary and its associated potential change are then missing. Furthermore, the electric potential and field at a given point are given by conditionally convergent infinite series, for which different summation schemes give different results. Nevertheless, standard simulation protocols can be used to compute experimental quantities unambiguously. In particular, using an auxiliary test particle and a multistep solvation path, we show that particle-based, Ewald, and common molecule-based summation schemes for the potential and field are all essentially equivalent. However, all methods require prior knowledge of the gas/liquid boundary potential to compute ionic solvation free energies using PBC protocols for both force-field and quantum-mechanical models.
凝聚相模拟通常使用周期性边界条件（PBCs）来表示热力学极限。对于离子从气相到液相的转移，气/液边界及其相关的势变化就会缺失。此外，给定点的电势和电场由条件收敛的无穷级数给出，不同的求和方案会给出不同的结果。然而，标准的模拟协议可用于明确计算实验量。特别是，使用一个辅助测试粒子和多步溶剂化路径，我们表明基于粒子、埃瓦尔德（Ewald）和基于常见分子的势与场的求和方案本质上都是等效的。但是，对于力场模型和量子力学模型，所有方法都需要气/液边界势的先验知识，以便使用PBC协议计算离子溶剂化自由能。
