过冷液体钾形核初期微观动力学机理的模拟研究

采用分子动力学方法对液态金属钾凝固过程进行了模拟,根据凝固过程体系平均原子能量、原子成键类型和成团类型,以及均方位移和非Gauss参数等动力学参数的演化特征,对过冷熔体形核初期微观动力学机理进行了研究.结果表明:根据过冷液体钾结晶形核过程热力学、动力学和结构特性的演化规律, 其过冷温度区间可以分为两个明显不同的阶段,潜在结晶核心出现在过冷液体较低温区.过冷熔体钾在形核初期,二十面体团簇结构在α-弛豫阶段逐渐解体,同时具有体心立方(bcc)结构的潜在结晶核心逐步形成,其临界晶核包含约300个原子.

Simulation study on the dynamic mechanisms of nucleation during the initial stage of supercooled liquid potassium

The solidification process of liquid metal potassium is simulated by using the molecular dynamics method.According to the evolution properties of average atomic energy in system,bonding type and clustering type among atoms,and the dynamic parameters of mean-square displacement and non-Gaussian parameter,the dynamic mechanisms in initial nucleation of supercooled liquid potassium are deeply studied.It is found that the supercooled liquid region can be divided into two different stages according to the evolutions of thermodynamic,dynamic and structural properties of supercooled liquid.And the potential crystallization nuclei appear in the lower temperature region of supercooled liquid.It is also found that the potential crystallization nuclei are formed with the disaggregations of icosahedron clusters during the a-relaxation regime,and the critical size of nucleus is about 300 atoms.