系列势阱深度下二元Lennard-Jones液体相分离程度的分子动力学研究  

Phase separation of binary Lennard-Jones liquids with a series of potential well depths investigated by molecular dynamics method

作　　者：张文惠 王丽娜 林佳玮 白世玉 赵兴宇 ZHANG Wen-hui;WANG Li-na;LIN Jia-wei;BAI Shi-yu;ZHAO Xing-yu(Xinjiang Laboratory of Phase Transitions and Microstructures in Condensed Matters,College of Physical Science and Technology,Yili Normal University,Yining 835000,China)

机构地区：[1]伊犁师范大学物理科学与技术学院,新疆凝聚态相变与微结构实验室,新疆伊宁835000

出　　处：《分子科学学报》2023年第3期253-263,共11页Journal of Molecular Science

基　　金：新疆维吾尔自治区自然科学基金资助项目(2021D01C465);伊犁师范大学博士科研启动基金资助项目(2022YSBS002)。

摘　　要：相分离是一种十分常见的现象,并得到了人们的广泛关注,但是究竟在怎样的微观相互作用下液体会产生相分离,其程度又是如何,仍然需要研究.本文通过分子动力学方法对系列势阱深度下二元Lennard-Jones液体进行了模拟研究,获得了液体相分离程度随两类原子势阱深度比值k的变化情况,给出了微观相分离下液体中同类原子聚集单元的典型图像,考察了相分离情况与原子间相互作用之间的关系.模拟所得的物理量包括各k值下平衡态液体中每个原子的最近邻原子是同类原子的几率的平均值、同类原子聚集单元的平均大小和所包含原子数的平均值、各瞬态图像中最大尺寸的聚集单元的平均大小和包含的原子数的平均值.上述物理量随k的增加都表现出了先缓慢增加,再快速增加,最后又变缓的变化特征.将这些量的变化特征与各k值下液体的瞬态图像和同类原子聚集单元的最大尺寸相结合,表明随着k的增加,二元Lennard-Jones液体依次能够出现没有相分离、微观相分离和宏观相分离3种状态.而且给出了液体从没有相分离向出现微观相分离的转变点和从出现微观相分离向出现宏观相分离的转变点所对应的k值,分别为2.47和2.89,揭示了液体出现微观相分离和宏观相分离所需要的微观相互作用条件,并且与其他文献中分子动力学模拟时所使用的参数以及所得结果具有一致性.在模拟结果的基础上,定性地解释了真实体系中的一些现象,并对相分离现象进行了热力学分析,表明液体中相分离是熵驱动和焓驱动竞争的结果.这些结果将为微观相互作用对液体相分离的影响情况及其热力学本质的理解产生重要的促进和启发作用.Phase separation is a very common phenomenon and is followed with interest widely.However,the microscopic interaction conditions for generating phase separation and its extent are still necessary to be investigated.In this paper,the binary Lennard-Jones liquids with a series of potential well depths are simulated by molecular dynamics method and some properties of phase separation in liquids are gained,which include the liquid phase separation extent versus the ratio k of potential well depth of two kinds of atoms,the typical image of aggregation unit of homogeneous atoms under microscopic phase separation and the relationship of phase separation and atomic interaction.The physical quantities of equilibrium liquids with each k obtained in simulations contain the average probability of homogeneous atom in the nearest neighbor ones,the average size and the average number of atoms in the aggregation units of homogeneous atoms(AUHA),as well as the average size of the largest aggregation units in each snapshot of liquids and the average number of atoms they include.The above physical quantities with rising k all increase slowly at first,then rapidly and slowly again at last.Combining the variation characteristics of the above quantities with the snapshots of the liquids of each k and the maximum size of AUHA,it is shown that with increasing k,the binary Lennard-Jones liquids could appear three states,no phase separation,microscopic phase separation and macroscopic phase separation,in turn.And the value of k is 2.47 corresponding to the transition points from no phase separation to microscopic phase separation,and 2.89corresponding to that from microscopic phase separation to macroscopic phase separation.The two transition points reveal the microscopic interaction conditions needed for microscopic phase separation and macroscopic phase separation of liquids,consistent with the parameters used in molecular dynamics simulation and the results obtained of other literatures.In addition,some phenomena of real systems are qu

关 键 词：相分离 二元液体 微观相互作用 分子动力学 

分 类 号：O641[理学—物理化学]