铝、锆液固态转变和动力学性质的第一性原理分子动力学研究

Study on the liquid-solid transition and dynamic properties of Al and Zr by ab initio molecular dynamic simulation

采用第一性原理分子动力学(Ab Initio Molecular Dynamics,AIMD)方法研究了Al和Zr液固转变过程中的能量、偶关联函数、结构因子和键对分布的变化规律,获得了不同温度下两种金属液体的扩散系数和黏度.结果表明,AIMD计算得到的液态金属偶关联函数、结构因子和扩散系数与实验测量数据符合得很好.在冷速为5.0×1013和2.5×1013K/s时,液态Al分别在730K附近发生玻璃化转变或者形成有一定缺陷的fcc晶体结构.在平均冷却速率为4.3×1013和2.0×1014K/s的条件下,液态Zr在1200K时分别开始转变为热力学上亚稳定的bcc结构和玻璃相.Zr的液态和玻璃态结构中二十面体和bcc类型短程序是其主要拓扑短程序.

The energitics, pair correlation functions （PCFs）, structure factors （SFs） and distribution of bond pairs during the liquid-solid transition of Al and Zr were studied by using ab initio molecular dynamics （AIMD） simulation.The diffusion coefficients and viscosities of liquid Al and Zr at different temperature were also calculated.It is shown that the AIMD calculated PCFs, SFs, and diffusion coefficients of liquid Al and Zr are in good agreement with the experimental results.At the average cooling rate of 5.0×1013 and 2.5×1013 K/s, liquid Al emerges glass transition at 730 K and is transformed into face centre cubic structure, respectively.Liquid Zr is transformed into thermodynamic metable body center cubic （bcc） and glassy structure, respectively around 1200 K when cooled at the average rate of 4.3×1013 and 2.0×1014 K/s.It is also shown that the structures of liquid and glassy Zr are mainly composed of icosahedral and bcc type of short range orders.