Molecular dynamics study of the transport properties and local structures of molten binary systems (Li, Na)Cl, (Li, K)Cl and (Na, K)Cl
Molecular dynamics study of the transport properties and local structures of molten binary systems (Li, Na)Cl, (Li, K)Cl and (Na, K)Cl
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DOI：
10.1016/j.molliq.2015.06.021
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发表时间：
2015-09
影响因子：
6
通讯作者：
Jia Wang;Jie Wu;Ze Sun;G. Lu;Jianguo Yu
中科院分区：
文献类型：
--
作者：
Jia Wang;Jie Wu;Ze Sun;G. Lu;Jianguo Yu
本文通过分子动力学模拟详细计算了 1100 K 下熔融碱二元氯化物 LiCl–NaCl、LiCl–KCl 和 KCl–NaCl 的结构和动态特性。计算并分析了LiCl对熔融氯化钠和氯化钾的自扩散系数、粘度和离子电导率等局部结构和输运性质的影响，以及氯化钠和氯化钾之间的混合效应。结果表明，随着熔融 LiCl-NaCl 和 LiCl-KCl 中 LiCl 含量的增加，Tosi-Fumi 势预测密度的负成分依赖性以及离子扩散率和离子电导率的正成分依赖性。随着 KCl 含量的增加，熔融 KCl-NaCl 的离子扩散率表现出较弱的成分依赖性。然而，密度和离子电导率表现出负的成分依赖性。这些混合熔体的输运性能由局部结构和原子间力决定。在这两个因素的影响下，混合物的剪切粘度先减小后增大。对于熔融的KCl或NaCl，随着较小的阳离子(Li+)的加入，反离子与阴离子之间的密堆积之间的相互作用减弱，而阳离子之间的密堆积被促进。而且，添加的离子越小，效果越明显。然而，添加较大的阳离子会产生相反的效果。
The structures and dynamic properties of molten alkali binary chlorides LiCl–NaCl, LiCl–KCl and KCl–NaCl at 1100 K have been calculated across the full composition range in this paper in detail by molecular dynamics simulations. The effects of LiCl on the local structures and transport properties as the self-diffusion coefficients, viscosities and ionic conductivities of molten NaCl and KCl as well as the mixing effects between NaCl and KCl have been calculated and analyzed. The results reveal that the Tosi-Fumi potential predicts negative composition dependence for density and positive composition dependences for ionic diffusivity and ionic conductivity as the contents of LiCl are increased for molten LiCl–NaCl and LiCl–KCl. As the KCl contents are increased, the ionic diffusivity of molten KCl–NaCl shows weak composition dependence. However, the density and ionic conductivity exhibit negative composition dependences. The transport performances of these mixed melts are dominated by the local structures and interatomic forces. The shear viscosities of the mixtures decrease firstly and then increase under the influences of these two factors. For molten KCl or NaCl, with the addition of a smaller cation (Li+), the interactions between counter ions and closed packs between anions are weakened, while closed packs between cations are promoted. What's more, the smaller the added ion is, the more pronounced the effects are. However, the addition of a larger cation presents the opposite effects.