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第一性原理计算镁合金层错能

时间:2019-03-02 14:01来源:毕业论文
基于DFT密度泛函理论计算镁的 型层错的层错能,之后是研究锆原子的铃木效应。作为模拟部分,其基础仍是密度泛函理论。之后。本课题的重点将是对杂质原子偏聚规律的统计学计算

摘要本课题主要分为两大部分。第一部分是基于DFT密度泛函理论计算镁的 型层错的层错能,之后是研究锆原子的铃木效应。作为模拟部分,其基础仍是密度泛函理论。之后。本课题的重点将是对杂质原子偏聚规律的统计学计算。在那里,层错将被视作一种特殊的相或者说相界,进而系综理论和化学反应平衡这两种方法将被用于推导层错中杂质原子的偏聚浓度。在低浓度下,两种方法给出一致的结果。另外,考虑更精细的细节后,精细处理后的结果将在一定条件下自然过渡到不精细的结果,因而我们的方法是自洽的。这些方法也是不依赖于具体模型的,因而它们也可用于估计其它类型缺陷或相界偏聚规律。热力学讨论之所以受到关注,是因为在实际应用中,研究人员往往想知道一种宏观因素是如何在整体趋势上影响层错能的,因而热力学估算将不失为一种简洁实用的方法。33531
关键词  层错能 密度泛函 热力学 铃木效应 偏聚
毕业论文设计说明书外文摘要
Title   First principle study of magnesium alloy stacking fault energy
Abstract
This project can be pided into two main parts. Each parts are then classified into some small sections. First of all ,  the generalized   type stacking fault energy of magnesium are calculated. Here density function theory (DFT) will serve us as a main tool, VASP code is also on the way. The second part is a little bit long, firstly, the role of solute atoms is to be considered . There Zr will be taken as our target atom. The method is also DFT first principle calculations. After that it is going to be tested whether the Zr solute atom do have a Suzuki effect. Finally, we again force our concentrations into thermodynamic parameters. We are going to undertake a systematic study on the segregation pattern of solute atoms,  first  the low-potency case will be considered then our method will be generalized to the case in which there is no such restriction and the interface interactions is of great importance. Our main tool of this section is the ensemble theory and chemical reaction equilibrium method and it happens that this two methods give the same results in low-potency case. The main reason that we favor thermodynamic discussions is its brevity and elegance, there is no need of specific models to further our studies and generalize our conclusions, also in practical applications it is neccessary to know how does the thermodynamic factors make an impact. 源`自*六)维[论*文'网www.lwfree.cn
Keywords Stacking fault energy DFT thermodynamic Suzuki segregation
目 录
1引言    1
1.1本研究的主要理论方法    1
1.1.1 镁及镁合金的介绍    1
1.1.2 镁中的层错与层错能    2
1.1.3 hcp-fcc结构相变    4
1.1.4 DFT密度泛函理论    5
       1.1.5 铃木气团    6
1.1.6 系综原理    7
1.2 本研究的主要工作内容    7
2   计算模拟部分    8
2.1 纯镁的层错能计算    8
2.1.1 alias-shear模型    8
2.1.2 DFT计算结果    10
   2.2参杂状态下镁的层错能计算    11
2.2.1 铃木效应    11
2.2.2 DFT计算结果    12
2.2.3 热力学讨论I:低浓度近似    13
2.2.4 热力学讨论II:精细处理    17
2.2.5 2.2.5热力学讨论III:更进一步的精细处理-考虑面间相互作用    20
结论    22
致  谢    25
参考文献26
1引言
1.1本研究的主要理论方法
1.1.1镁及镁合金的介绍 I镁及镁合金的性能 第一性原理计算镁合金层错能:http://www.lwfree.cn/cailiao/20190302/30688.html
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