晶格反演修正型嵌入原子势函数理论及应用研究

发布时间：2018-01-11 06:05

本文关键词：晶格反演修正型嵌入原子势函数理论及应用研究　出处：《华中科技大学》2015年博士论文　论文类型：学位论文

【摘要】：随着计算机软硬件性能的提升和互联网技术的发展,计算材料学在新材料研发中起到了越来越重要的作用。作为其中的一个重要分支,分子动力学在进行原子尺度上模拟中得到了广泛的应用。尽管分子动力学方法涉及到众多的技术,但势函数因着其对计算结果可靠性的决定性作用而成为最受人们关注的一个,几乎伴随着分子动力学方法的整个发展历程。时至今日,人们仍在尝试开发出具有更高精度、更高效率和更高扩展性的势函数。本文的主要研究工作也是围绕这一主题展开,特别是引入了晶格反演法作为势函数开发的工具。下面是对本文主要工作的简单总结。首先,使用晶格反演法,以第一性原理计算的结合能曲线为基础,发展了适用于Pd-Au间的反演对势。然后以该对势为基础,研究了Pd-Au合金纳米颗粒熔化行为的尺寸效应及表面原子偏聚现象。其次,在修正型嵌入原子势(MEAM)的基础上,通过移除其中所使用的复杂的多体屏蔽函数,并使用晶格反演法考虑更多近邻原了对对势和电子密度的贡献,提出了一种新的势函数模型,即晶格反演修正型嵌入原子势(LI-MEAM)。相比于之前的MEAM势函数,LI-MEAM的模型更简单,势参数更少,物理意义更明确,同时精度也有提高。除此之外,在纳米颗粒的应用中,LI-MEAM表现出更好的稳定性。第三,使用粒子群优化算法优化了Fe在LI-MEAM下的势参数。然后使用优化的势参数,计算了Fe的各种物理性质,并将这些结果与实验值及其他势函数的计算结果进行比较。对比结果显示,作为一种简化的MEAM势函数,LI-MEAM仍然具有略高于第二近邻的修正型嵌入原子势(2NN MEAM)的精度。另外还使用LI-MEAM研究了bcc-Fe球形纳米颗粒熔化行为的尺寸效应及熔化机理。最后,使用粒子群优化算法优化了所有过渡族bcc体系(Fe、Cr、Mo、V、Nb及Ta)在LI-MEAM下的势参数。然后使用这些优化的势参数,计算了各个过渡族bcc体系的多种物理性质,并将这些结果与实验值及2NN MEAM的计算结果进行比较。结果显示,在LI-MEAM势函数下使用这些参数计算出的各体系的物理性质具有很高的精度。
[Abstract]:With the improvement of computer hardware and software performance and the development of Internet technology, computational materials science plays an increasingly important role in the research and development of new materials. Molecular dynamics has been widely used in atomic scale simulations, although molecular dynamics methods involve many techniques. However, the potential function has become the most concerned because of its decisive effect on the reliability of the calculation results, and almost accompanied by the entire development of molecular dynamics methods. People are still trying to develop potential functions with higher accuracy, higher efficiency and higher expansibility. In particular, the lattice inversion method is introduced as a tool for the development of potential functions. The following is a brief summary of the main work in this paper. First, using lattice inversion method, based on the binding energy curve calculated by first principle, the inversion potential suitable for Pd-Au is developed, and then it is based on this pair potential. The size effect of the melting behavior of Pd-Au alloy nanoparticles and the phenomenon of surface atomic segregation were studied. Secondly, based on the modified embedded atom potential (MEAM), the complex multibody shielding function is removed. The lattice inversion method is used to consider the contribution of more nearest neighbors to the potential and electron density, and a new potential function model is proposed. That is, the lattice inversion modified embedded atom potential LI-MEAM is simpler than the previous MEAM potential function and has fewer potential parameters and clearer physical meaning. In addition, LI-MEAM shows better stability in the application of nanoparticles. Thirdly, particle swarm optimization algorithm is used to optimize the potential parameters of Fe under LI-MEAM, and then the physical properties of Fe are calculated by using the optimized potential parameters. These results are compared with experimental values and other potential functions. The results show that these results are a simplified MEAM potential function. LI-MEAM still has a modified embedded atomic potential slightly higher than the second nearest neighbor. LI-MEAM was also used to study the size effect and melting mechanism of bcc-Fe spherical nanoparticles. Finally, the particle swarm optimization algorithm is used to optimize all transition bcc systems. The potential parameters of NB and Ta) under LI-MEAM are used to calculate the physical properties of each transition family bcc system. These results are compared with experimental values and 2NN MEAM results. The physical properties of each system calculated by using these parameters under the LI-MEAM potential function have high accuracy.
【学位授予单位】：华中科技大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TB383.1

【相似文献】