Lin Shiang-Tai, Hsieh Chieh-Ming
Department of Chemical Engineering, National Taiwan University, Taipei 10617, Taiwan.
J Chem Phys. 2006 Sep 28;125(12):124103. doi: 10.1063/1.2354489.
A new approach is proposed to enhance the efficiency and accuracy for calculation of the long-range electrostatic interaction from implicit solvation models, i.e., the polarizable continuum model (PCM) and its variants, conductorlike PCM/conductorlike screening model and integral equation formalism PCM. In these methods the solvent electrostatics effects are represented by a set of discrete apparent charges distributed on tesserae of the molecular cavity surface embedding the solute. In principle, the accuracy of these methods is improved if the cavity surface is tessellated to finer tesserae; however, the computational time is increased rapidly. We show that such undesired dependency between accuracy and efficiency is a result of the inaccurate treatment of the apparent charge self-contribution to the potential and/or electric field. By taking into account the full effects due to the size and curvature of the segment occupied by each apparent charge, the error in calculated electrostatic solvation free energy is essentially zero for ions (point charge at the center of a sphere) regardless of the degree of tessellation used. For molecules where gradient of apparent charge density is nonzero at the cavity surface, we propose a multiple-sampling technique which significantly lowers the calculated error compared to the original PCM methods, especially when very few numbers of tesserae are used.
本文提出了一种新方法，以提高基于隐式溶剂化模型（即可极化连续介质模型（PCM）及其变体、类导体PCM/类导体屏蔽模型和积分方程形式PCM）计算长程静电相互作用的效率和准确性。在这些方法中，溶剂静电效应由分布在嵌入溶质的分子腔表面镶嵌块上的一组离散表观电荷表示。原则上，如果将腔表面细分为更精细的镶嵌块，这些方法的准确性会提高；然而，计算时间会迅速增加。我们表明，这种准确性和效率之间的不良依赖关系是由于表观电荷对电势和/或电场的自贡献处理不准确所致。通过考虑每个表观电荷所占片段的大小和曲率的全部影响，对于离子（球体中心的点电荷），无论使用何种细分程度，计算得到的静电溶剂化自由能误差基本为零。对于在腔表面表观电荷密度梯度不为零的分子，我们提出了一种多重采样技术，与原始PCM方法相比，该技术显著降低了计算误差，尤其是在使用非常少量镶嵌块的情况下。
