Yang Yong, Meng Sheng
Institute of Physics, Chinese Academy of Sciences, Box 603, Beijing 100080, China.
J Chem Phys. 2007 Jan 28;126(4):044708. doi: 10.1063/1.2431363.
The early stage of heterogeneous nucleation of NaCl from supersaturated NaCl aqueous solution at the water-NaCl (001) interface has been investigated by molecular dynamics simulations. The critical size of the nuclei for spontaneous growth was found to be as small as two atoms (a Na(+)-Cl(-) ion pair) at high supersaturation. Due to the presence of a relatively stable water network and the effect of the hydration force at the interface, the stable nuclei formed on the NaCl (001) are found to contain more Na(+) ions than Cl(-) ions. The different deposition characteristics of the Na(+) and Cl(-) solutes lead to a positively charged substrate and thus may introduce another driving force for nucleation besides the level of solution supersaturation. The role of water was further confirmed by comparison with NaCl epitaxy growth in the vacuum.
通过分子动力学模拟研究了在水 - NaCl(001)界面上，从过饱和NaCl水溶液中异质成核形成NaCl的早期阶段。发现在高过饱和度下，自发生长的核的临界尺寸小至两个原子（一个Na(+) - Cl(-)离子对）。由于相对稳定的水网络的存在以及界面处水化力的作用，发现在NaCl(001)上形成的稳定核中Na(+)离子比Cl(-)离子更多。Na(+)和Cl(-)溶质的不同沉积特性导致衬底带正电，因此除了溶液过饱和度水平之外，可能还会引入另一种成核驱动力。通过与真空中NaCl外延生长的比较，进一步证实了水的作用。
