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运用分子动力学方法对比模拟研究了碳化硅的体熔化、表面熔化和晶体生长过程.分别采用MEAM势和Tersoff势两种势函数描述碳化硅.结果表明:体熔化时,两种势函数描述的SiC的原子平均能量、Lindemann指数和结构有序参数与温度的变化关系相似,但MEAM势对应的体熔点(4250 K)比Tersoff势(4750 K)的要高.表面熔化时,两种势函数描述的SiC在相同的过热度下熔化速度相近;而在相同的温度条件下,MEAM作用的SiC表面熔化速度更快.这是由于MEAM势SiC的热力学熔点(3338 K)低于Tersoff势SiC的热力学熔点(3430 K)的缘故.两种势函数作用的SiC在晶体生长方面差异很大.MEAM势SiC的晶体生长速度与过冷度有关,过冷度约为400 K时晶体生长速度最快.但Tersoff势SiC晶体却在过冷度为0—1000 K的范围内均不能生长.综合考虑,MEAM势比Tersoff势能更好地描述碳化硅的熔化和凝固行为.
Molecular dynamics simulation was used to simulate the bulk melting, surface melting and crystal growth of SiC. Two kinds of potential functions, MEAM and Tersoff, were used to describe SiC respectively. The results show that when the bulk melts, The average atomic energy, Lindemann index and structure order parameter of SiC are similar to the change of temperature, but the body melting point (4250 K) corresponding to MEAM potential is higher than that of Tersoff potential (4750 K) .When the surface melts, The SiC melts at the same degree of superheat have similar melting rates, but at the same temperature, the surface melting rate of MEAM melts faster, because the thermodynamic melting point (3338 K) of the MEAM-type SiC is lower than that of the Tersoff-type SiC The thermodynamic melting point (3430 K), the two kinds of potential function of SiC in the crystal growth is very different.MEME potential SiC growth rate and undercooling, under about 400 K under the crystal growth rate of the fastest However, the Tersoff potential SiC crystals failed to grow in the undercooled range of 0 to 1000 K. Combining the MEAM potential with the Tersoff potential, the melting and solidification behavior of SiC was better described.