ABSTRACT The molecular dynamics (MD) method is a promising technique to dissect the atomistic details of water dynamics around a solute. However, the quantitative predictions of experimentally measured kinetic properties, e.g. translational diffusion coefficient (D) and rotational relaxation time (τ), are not straightforward. Current water models have failed to reproduce these properties quantitatively; therefore, the fine-tuning of water models is required. In this study, we examined the effects of ion–water Lennard-Jones (LJ) potentials on the water dynamics around a monovalent atomic ion. For the TIP5P water model, we introduced new LJ potentials for the ion–hydrogen and ion–pseudoatom interactions, which were zero in the original TIP5P model. The hydration properties, i.e. D, τ, and the radius of the first hydration shell (rMO), were examined for various parameter settings. As a result, the new parameters certainly improved the reproducibility of the hydration properties in correspondence with experimental values. However, it is still difficult to reproduce faster rotational relaxation of hydration water than that of bulk water. In addition, we found that the three hydration properties (D, τ, and rMO) were artificially correlated in the MD simulations.

中文翻译：

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离子-水 Lennard-Jones 势对分子动力学模拟中单价原子离子周围水合动力学的影响

摘要 分子动力学 (MD) 方法是一种很有前景的技术，可以解析围绕溶质的水动力学的原子细节。然而，实验测量的动力学特性的定量预测，例如平移扩散系数 (D) 和旋转弛豫时间 (τ)，并不简单。当前的水模型未能定量地再现这些特性；因此，需要对水模型进行微调。在这项研究中，我们研究了离子-水 Lennard-Jones (LJ) 势对单价原子离子周围水动力学的影响。对于 TIP5P 水模型，我们为离子-氢和离子-伪原子相互作用引入了新的 LJ 势，这在原始 TIP5P 模型中为零。水化性质，即 D、τ 和第一水化壳的半径 (rMO)，检查了各种参数设置。因此，新参数确实提高了与实验值相对应的水合特性的再现性。然而，仍然难以再现水合水比散装水更快的旋转弛豫。此外，我们发现三个水合特性（D、τ 和 rMO）在 MD 模拟中是人为关联的。