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arXiv 2109.07527cond-mat.softcond-mat.stat-mech
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电荷调节效应的加速模拟方法

Accelerated simulation method for charge regulation effects

Tine Curk, Jiaxing Yuan, Erik Luijten

摘要:

从聚电解质和生物分子到带电纳米颗粒和膜的溶剂化实体的净电荷取决于各个可电离基团的局部解离平衡。将这种现象\emph{charge regulation}纳入理论和计算模型需要动态的、依赖于构型的表面电荷重新计算,因此通常通过假设颗粒上的净电荷恒定来近似。存在解决这个问题的各种计算方法。我们提出了一种替代的,特别是有效的电荷调节蒙特卡罗方法(CR-MC),它明确地模拟个别电荷的重新分配,并准确地采样正确的巨正则电荷分布。此外,我们提供了一个开源的LAMMPS分子动力学(MD)模拟包的实现,从而在混合MD/CR-MC模拟方法。该实施方案旨在处理广泛的隐式溶剂系统,该系统模拟离散的可电离基团或表面位点。该方法的计算成本与可电离基团的数量成线性比例,从而允许精确模拟包含数千个可电离位点的系统。作为说明,我们使用CR-MC方法来量化电荷调节对螺旋-小球过渡的性质和带相反电荷的纳米颗粒之间的有效相互作用的影响。

英文摘要:

The net charge of solvated entities, ranging from polyelectrolytes and biomolecules to charged nanoparticles and membranes, depends on the local dissociation equilibrium of individual ionizable groups. Incorporation of this phenomenon, \emph{charge regulation}, in theoretical and computational models requires dynamic, configuration-dependent recalculation of surface charges and is therefore typically approximated by assuming constant net charge on particles. Various computational methods exist that address this. We present an alternative, particularly efficient charge regulation Monte Carlo method (CR-MC), which explicitly models the redistribution of individual charges and accurately samples the correct grand-canonical charge distribution. In addition, we provide an open-source implementation in the LAMMPS molecular dynamics (MD) simulation package, resulting in a hybrid MD/CR-MC simulation method. This implementation is designed to handle a wide range of implicit-solvent systems that model discreet ionizable groups or surface sites. The computational cost of the method scales linearly with the number of ionizable groups, thereby allowing accurate simulations of systems containing thousands of individual ionizable sites. By matter of illustration, we use the CR-MC method to quantify the effects of charge regulation on the nature of the polyelectrolyte coil--globule transition and on the effective interaction between oppositely charged nanoparticles.

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