论文标题
使用快速多极方法中和均匀分布的背景电荷中和的带电系统的精确静电能计算及其在有效的自由能计算中的应用
Exact electrostatic energy calculation for charged systems neutralized by uniformly distributed background charge using fast multipole method and its application to efficient free energy calculation
论文作者
论文摘要
在离子和离子分子的自由能的分子动力学计算中，我们经常遇到断裂电气中性条件的湿电荷分子系统。这在周期性边界条件下评估静电相互作用时会引起问题。该问题的标准补救措施是考虑一个假设的均匀背景电荷密度以中和总系统。在这里，我们提出了一个新的表达式，用于评估系统的静电相互作用，包括快速多极方法（FMM）的背景电荷。此外，已经开发了一种通过FMM评估溶质 - 溶剂相互作用能量的有效方案，以减少远场部分的计算。我们已经计算了离子的水合自由能，mg $^{2+} $，na $^{+} $，以及使用新表达式溶解在中性溶剂中的cl $^{ - } $。计算出的自由能与建立良好的粒子网埃瓦尔德方法与结果非常一致，证明了在FMM框架中本表达的有效性。本方案的一个优点是基于高度平行的计算的大规模带电系统（尤其是百万个颗粒）的有效自由能计算。
In the molecular dynamics calculations for the free energy of ions and ionic molecules, we often encounter wet charged molecular systems where electrical neutrality condition is broken. This causes a problem in the evaluation of electrostatic interaction under periodic boundary condition. A standard remedy for the problem is to consider a hypothetical homogeneous background charge density to neutralize the total system. Here, we present a new expression for the evaluation of electrostatic interactions for the system including the background charge by fast multipole method (FMM). Further, an efficient scheme to evaluate solute-solvent interaction energy by FMM has been developed to reduce the computation of far-field part. We have calculated hydration free energy of ions, Mg$^{2+}$, Na$^{+}$, and Cl$^{-}$ dissolved in neutral solvent using the new expression. The calculated free energy showed a good agreement with the result using well-established particle mesh Ewald method, demonstrating the validity of the present expression in the framework of FMM. An advantage of the present scheme is in an efficient free energy calculation of a large-scale charged systems (particularly over million particles) based on highly parallel computations.
