All atom molecular dynamics simulations of uranyl ions in supercritical water are used to dissect the effects of concentration of uranyl ions and density of water on various structural and dynamic properties of the solutions. The analyses of radial distribution functions as a function of concentration of the uranyl ion and water density reveal that the effect of the former on the local structure is negligible as compared to the same of the later. The number of hydration water of the uranyl ion has been observed to increase with increasing density of the water, but it decreases with the increasing concentration of the uranyl ions. The orientational distributions are observed to be independent of variation in concentration of the uranyl ion, same as the case was with water density. The translational and rotational dynamics of the water molecules have been investigated from the respective mean squared displacements and time correlation functions. Although increase of both the concentration of the uranyl ions and the density of water reduces translational diffusivity of water as well as uranyl ions, the effect of changing water density is more than that of uranyl concentrations. However, orientational relaxation of various molecular vectors of the water molecule is practically unchanged with any variation in concentration of the uranyl ions and it changes only slightly with the change in water density. Unlike at ambient condition, orientational dynamics at supercritical conditions remains virtually unchanged with the change in uranyl ion concentration.

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超临界水中硝酸铀酰水合的分子动力学模拟研究：从溶剂密度上剖析铀酰离子浓度的影响

用超临界水中的铀酰离子的所有原子分子动力学模拟分析了铀酰离子的浓度和水的密度对溶液的各种结构和动力学性质的影响。径向分布函数与铀酰离子浓度和水密度的关系分析表明，与后者相比，前者对局部结构的影响可忽略不计。已经观察到铀酰离子的水合水的数量随着水的密度增加而增加，但是随着铀酰离子的浓度的增加而减少。与水密度的情况相同，观察到取向分布与铀酰离子浓度的变化无关。已经从各自的均方位移和时间相关函数研究了水分子的平移和旋转动力学。尽管增加铀酰离子的浓度和水的密度都降低了水以及铀酰离子的平移扩散率，但是改变水密度的影响大于铀酰浓度的影响。但是，水分子的各种分子载体的取向弛豫几乎没有改变，而铀酰离子的浓度有任何变化，并且随水密度的变化而仅略有变化。与环境条件不同，随着铀酰离子浓度的变化，超临界条件下的取向动力学几乎保持不变。