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  本文關鍵詞：晶格反演修正型嵌入原子勢函數(shù)理論及應用研究　出處：《華中科技大學》2015年博士論文　論文類型：學位論文

  更多相關文章： 分子動力學 勢函數(shù) 多體勢 修正型嵌入原子勢 第二近鄰修正型嵌入原子勢 品格反演法 多體屏蔽函數(shù) 勢參數(shù)優(yōu)化 過渡族bcc金屬

【摘要】：隨著計算機軟硬件性能的提升和互聯(lián)網(wǎng)技術的發(fā)展,計算材料學在新材料研發(fā)中起到了越來越重要的作用。作為其中的一個重要分支,分子動力學在進行原子尺度上模擬中得到了廣泛的應用。盡管分子動力學方法涉及到眾多的技術,但勢函數(shù)因著其對計算結果可靠性的決定性作用而成為最受人們關注的一個,幾乎伴隨著分子動力學方法的整個發(fā)展歷程。時至今日,人們仍在嘗試開發(fā)出具有更高精度、更高效率和更高擴展性的勢函數(shù)。本文的主要研究工作也是圍繞這一主題展開,特別是引入了晶格反演法作為勢函數(shù)開發(fā)的工具。下面是對本文主要工作的簡單總結。 首先,使用晶格反演法,以第一性原理計算的結合能曲線為基礎,發(fā)展了適用于Pd-Au間的反演對勢。然后以該對勢為基礎,研究了Pd-Au合金納米顆粒熔化行為的尺寸效應及表面原子偏聚現(xiàn)象。 其次,在修正型嵌入原子勢(MEAM)的基礎上,通過移除其中所使用的復雜的多體屏蔽函數(shù),并使用晶格反演法考慮更多近鄰原了對對勢和電子密度的貢獻,提出了一種新的勢函數(shù)模型,即晶格反演修正型嵌入原子勢(LI-MEAM)。相比于之前的MEAM勢函數(shù),LI-MEAM的模型更簡單,勢參數(shù)更少,物理意義更明確,同時精度也有提高。除此之外,在納米顆粒的應用中,LI-MEAM表現(xiàn)出更好的穩(wěn)定性。 第三,使用粒子群優(yōu)化算法優(yōu)化了Fe在LI-MEAM下的勢參數(shù)。然后使用優(yōu)化的勢參數(shù),計算了Fe的各種物理性質,并將這些結果與實驗值及其他勢函數(shù)的計算結果進行比較。對比結果顯示,作為一種簡化的MEAM勢函數(shù),LI-MEAM仍然具有略高于第二近鄰的修正型嵌入原子勢(2NN MEAM)的精度。另外還使用LI-MEAM研究了bcc-Fe球形納米顆粒熔化行為的尺寸效應及熔化機理。 最后,使用粒子群優(yōu)化算法優(yōu)化了所有過渡族bcc體系(Fe、Cr、Mo、V、Nb及Ta)在LI-MEAM下的勢參數(shù)。然后使用這些優(yōu)化的勢參數(shù),計算了各個過渡族bcc體系的多種物理性質,并將這些結果與實驗值及2NN MEAM的計算結果進行比較。結果顯示,在LI-MEAM勢函數(shù)下使用這些參數(shù)計算出的各體系的物理性質具有很高的精度。
[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.
【學位授予單位】：華中科技大學
【學位級別】：博士
【學位授予年份】：2015
【分類號】：TB383.1

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本文編號：1408375