Department of Chemistry, University of Basel, Klingelbergstrasse 80, CH-4056 Basel, Switzerland.
J Chem Phys. 2017 Oct 28;147(16):161712. doi: 10.1063/1.4993424.
Most empirical force fields use atom-centered point charges (PCs) to represent the electrostatic potential (ESP) around molecules. While such PC models are computationally efficient, they are unable to capture anisotropic electronic features, such as σ holes or lone pairs. These features are better described using atomic multipole (MTP) moments, which significantly improve the quality of the resulting ESP. However, the improvement comes at the expense of a considerably increased computational complexity and cost for calculating the interaction energies and forces. In the present work, a novel minimal distributed charge model (MDCM) based on off-centered point charges is presented and the quality of the resulting ESP is compared to the performance of MTPs and atom-centered PC models for several test molecules. All three models are fitted using the same algorithm based on differential evolution, which is available as a Fortran90 program from the authors upon request. We show that the MDCM is capable of approximating the reference ab initio ESP with an accuracy as good as, or better than, MTPs without the need for computationally expensive higher order multipoles. Further it is demonstrated that the MDCM is numerically stable in molecular dynamics simulations and is able to reproduce electrostatic interaction energies and thermodynamic quantities with the same accuracy as MTPs at reduced computational cost.
大多数经验力场使用基于原子中心的点电荷（PCs）来表示分子周围的静电势（ESP）。虽然这种 PC 模型计算效率高，但它们无法捕捉各向异性的电子特征，如σ孔或孤对电子。这些特征使用原子多极矩（MTP）矩来描述效果更好，这显著提高了所得 ESP 的质量。然而，这种改进是以显著增加计算能量和力相互作用的计算复杂度和成本为代价的。在本工作中，提出了一种基于偏心点电荷的新型最小分布式电荷模型（MDCM），并将所得 ESP 的质量与 MTP 和基于原子中心的 PC 模型在几个测试分子上的性能进行了比较。所有三种模型都使用基于差分进化的相同算法进行拟合，该算法可根据要求以 Fortran90 程序的形式从作者处获得。我们表明，MDCM 能够以与 MTP 相同或更好的精度来近似参考从头算 ESP，而无需计算成本高的更高阶多极矩。此外，还证明 MDCM 在分子动力学模拟中是数值稳定的，并且能够以与 MTP 相同的精度再现静电相互作用能量和热力学量，同时降低计算成本。
