简单分子液体中的相转变机制研究

简单液体中的相转变是近些年来新发现的物理现象。对于发生在过冷区的液液相转变通常可以用“两态”液体模型进行解释。而对于发生在熔化曲线以上且临界点远远高于熔化曲线的简单分子液体中的相转变机制还很不清楚。本项目拟采用第一性原理分子动力学结合固有结构法，对简单分子液态H2、N2、P4、CH4、As4S4进行研究。计算其宏观热力学状态方程V=V(T, P)，寻找液液相转变的证据，确定临界点的位置。研究液体的微观固有结构和动力学性质，揭示在临界点以下以及超临界区域内它们随外界条件的变化规律，从而阐明这些简单分子液体中相转变发生的微观机制。本项目不仅可以丰富对液液相转变这一新颖物理现象的理论研究；还可以对超临界流体的研究，以及材料的制备、物相的获取等提供有指导意义的理论信息。

Phase transition in simple liquids is a new type of physical phenomena found in recent years. For the phase transition that occurs in supercooled region, “two states” liquid model can be used to explain its mechanism. However, in some simple molecular liquids, the phase transition occurs above and the critical point is much higher than the melting curve. In this case, the mechanism of liquid-liquid phase transition (LLPT) is still unclear up to now. In this project, we will use the frist-principle molecular dynamics and inherent structure formalism to study the LLPT in some simple molecular liquids, including liquid H2，N2，P4，CH4，As4S4. The macroscopic thermodynamic equation of state V=V(T, P) of these systems will be calculated to find direct evidence of the first-order LLPT and to determine the position of critical point. The microscopic inherent structure and dynamical properties will be studied and their change with external conditions such as temperature or pressure will be discovered to clarify the mechanism of LLPT in these molecular liquids. The research can not only enrich the theoritical study of LLPT but also provide insightful information to the study of supercritical fluid，material preparation, acquisition of phases, etc..