Molecular dynamics simulation of NaCl dissolution.
Molecular dynamics simulation of NaCl dissolution.
复制标题
氯化钠溶解的分子动力学模拟。
DOI：
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发表时间：
2015
影响因子：
3.3
通讯作者：
G. Patey
中科院分区：
文献类型：
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作者：
G. Lanaro;G. Patey
采用分子动力学模拟方法研究了NaCl纳米晶（含102400个离子）在水中的溶解行为。我们专注于系统在300 K的下沉条件下，但浓度和温度的影响也进行了研究。立方体，球形，片状，棒状纳米晶体被认为是，它表明，初始形状可以影响溶解过程。溶解过程分为三个阶段：第一阶段，晶体表面的大部分暴露离子被去除，晶体呈现出溶液退火的形状，并在整个第二阶段持续存在;第二个较长的中间阶段，溶解大致遵循固定速率定律;最后一个阶段，小的残留晶体（约200个离子）以不断增加的速率溶解，直到它消失。适用于大多数溶解过程的溶解的第二阶段由经典速率方程很好地描述，所述经典速率方程简单地假设溶解速率与离子最容易从晶体分离的活性表面积成比例。有效面积取决于初始晶体形状。我们表明，对于我们的模型NaCl纳米晶体的速率决定步骤，在水槽条件下溶解离子脱离晶体，并扩散层不存在这些系统。
Molecular dynamics simulations are used to investigate the dissolution of NaCl nanocrystals (containing ∼2400 ions) in water. We focus on systems under sink conditions at 300 K, but the influences of concentration and temperature are also investigated. Cubical, spherical, tablet-shaped, and rod-shaped nanocrystals are considered, and it is shown that the initial shape can influence the dissolution process. Dissolution is observed to occur in three stages: an initial period where the most exposed ions are removed from the crystal surface, and the crystal takes on a solution-annealed shape which persists throughout the second stage of dissolution; a second long intermediate stage where dissolution roughly follows a fixed rate law; and a final stage where the small residual crystal (≲200 ions) dissolves at an ever increasing rate until it disappears. The second stage of dissolution which applies for most of the dissolution process is well described by classical rate equations which simply assume that the dissolution rate is proportional to an active surface area from which ions are most easily detached from the crystal. The active area depends on the initial crystal shape. We show that for our model NaCl nanocrystals the rate-determining step for dissolution under sink conditions is ion detachment from the crystal, and that diffusion layers do not exist for these systems.