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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Atomic charges derived from electrostatic potentials for molecular and periodic systems
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Atomic charges derived from electrostatic potentials for molecular and periodic systems

机译：源自分子和周期系统静电势的原子电荷

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We present a method for fitting atomic charges to the electrostatic potential (ESP) of periodic and nonperiodic systems. This method is similar to the method of Campa?á et al. [J. Chem. Theory Comput. 2009, 5, 2866 ]. We compare the Wolf and Ewald long-range electrostatic summation methods in calculating the ESP for periodic systems. We find that the Wolf summation is computationally more efficient than the Ewald summation by about a factor of 5 with comparable accuracy. Our analysis shows that the choice of grid mesh size influences the fitted atomic charges, especially for systems with buried (highly coordinated) atoms. We find that a maximum grid spacing of 0.2-0.3 ? is required to obtain reliable atomic charges. The effect of the exclusion radius for point selection is assessed; we find that the common choice of using the van der Waals (vdW) radius as the exclusion radius for each atom may result in large deviations between the ESP generated from the ab initio calculations and that computed from the fitted charges, especially for points closest to the exclusion radii. We find that a larger value of exclusion radius than commonly used, 1.3 times the vdW radius, provides more reliable results. We find that a penalty function approach for fitting charges for buried atoms, with the target charge taken from Bader charge analysis, gives physically reasonable results.
机译：我们提出了一种将原子电荷拟合为周期性和非周期性系统的静电势（ESP）的方法。此方法类似于Campa？á等人的方法。 [J.化学理论计算。 2009，5，2866]。在计算周期系统的ESP时，我们比较了Wolf和Ewald远程静电求和方法。我们发现Wolf求和在计算上比Ewald求和高出大约5倍，并且具有相当的精度。我们的分析表明，网格尺寸的选择会影响拟合的原子电荷，特别是对于具有埋藏（高度协调）原子的系统。我们发现最大网格间距为0.2-0.3？需要获得可靠的原子电荷。评估排除半径对点选择的影响;我们发现，使用范德华（vdW）半径作为每个原子的排斥半径的常见选择可能会导致从头算计算和拟合电荷计算得出的ESP之间存在较大偏差，尤其是对于最接近的点排除半径。我们发现，排除半径的值比常用值大，是vdW半径的1.3倍，可提供更可靠的结果。我们发现，采用惩罚函数方法拟合埋原子的电荷，并从Bader电荷分析中提取目标电荷，可以得出物理上合理的结果。

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