空位晶体相场模型模拟二维晶体相形貌图

Phase Field Model Simulation of Bumps and Holes Pattern of Two Dimension Crystals

[目的]揭示空位晶体相场模型(VPFC)中二维周期性晶体相空位缺陷结构形貌。[方法]对标准晶体相场模型的自由能函数进行修正得到空位晶体相场模型,再利用空位晶体相场方程,研究二维相图中不同相晶体结构形貌图,以及晶体结构中出现空位的条件。[结果]当平均原子密度数值位于不同晶体相时,呈现出不同的二维周期性晶体结构形貌图。[结论]将晶体结构形貌图与其原子密度曲线对照,可见该模型中晶体相结构主要有六角"凸起"相、条状相和六角"凹坑"相。当平均原子密度数值位于相图中局部粒子相和六角"凸起"相之间时,二维周期性晶体结构中将出现空位,并且晶粒内部空位随机分布,空位数目与原子密度值有关。

[Objective]The vacancy morphology of two-dimensional periodic crystal structure was estimated through the vacancy phase field crystal (VPFC)model.[Methods]The free energy function of VPFC model was obtained by modifying simple phase field crystal model.The VPFC model was used to study the different periodic crystal profiles in the two-dimensional phases diagram and explore the condition of vacancy presenting.[Results]Different kinds of the two-dimensional periodic crystal structure patterns were obtained by selecting the average a-tomic density values in different phases.[Conclusion]Combining topography of crystal structure with atomic density curve reveals that hexagonal bumps,stripes and hexagonal holes are main structures in the crystal sample.When the average atomic density value is located in the phase diagram of the coexistence zone of the local particles and hexagonal bumps phase,vacancy structures appear in the crystal.Moreover,the vacancies are randomly distributed and their number are related to the atomic density values.