温度和压力诱导的无序金属的原子结构演化与相变

发布时间：2022-12-11 10:22

　　本文通过实验和理论相结合的方式,研究了 Au55Cu25Si20金属玻璃的结构特征以及它在高温和高压下的行为,同时也探究了Ca,Al金属液体以及Ca72.7Al27.3金属合金在高温高压下的结构演变。Au55Cu25Si20金属玻璃的结构特征表现为局域原子的堆积以9,10,11配位的多面体为主,而不是以类二十面体团簇为主,同时这些9,10,11配位的多面体中小尺寸的团簇互相排斥,而大尺寸的团簇互相吸引。这种异常的原子堆积结构限制了该金属玻璃的玻璃形成能力,并导致了结构因子第一峰出现异常的峰肩。通过用5%的Ag替换Cu,Au55Cu20Ag5Si20金属玻璃的空间连接性和原子堆积密度得到了大幅度提升,从而提高了玻璃形成能力,这与实验结果也是相吻合的。应用原位高压X射线衍射实验技术和第一性原理分子动力学模拟,对Au55Cu25Si20金属玻璃在压力诱导下的结构变化进行了研究,并持续加压到了36.8GPa。研究发现,Au55Cu25Si20金属玻璃的非晶态-非晶态相变发生在13.1到15.8 GPa之间,并且在降压的过程中该相变是可逆的。理论研究与实验研究的结果相一致,揭示了在高压和低压下A... 

【文章页数】：177 页

【学位级别】：博士

【文章目录】：
Abstract (English)
Abstract (Chinese)
Acknowledgements
Abbreviations
Chapter One
    1 Introduction
        1.1. Introduction to metallic glasses
        1.2. Introduction to metallic liquids
        1.3. Thesis outlines
Chapter Two
    2 Experimental and theoretical methods and setups
        2.1. Samplepreparation
            2.1.1. Preparation of metallic glasses
        2.2. Diamond anvil cell (DAC)
            2.2.1. Principle
            2.2.2. Major components of DAC
            2.2.3. Heating
            2.2.4. Synchrotron radiation
        2.3. Theoretical methods
            2.3.1. First-principles method
            2.3.2. Density functional theory
            2.3.3. Computational framework
            2.3.4. Structural analysis methods
Chapter Three
    3 Structural signature in Au-based metallic glasses
        3.1. Introduction
        3.2. Materials and methods
            3.2.1. Sample preparation
            3.2.2. Simulation details
        3.3. Results and discussion
        3.4. Summary
Chapter Four
    4 Pressure-induced phase transformation in Au_(55)Cu_(25)Si_(20) metallic glass
        4.1 Introduction
        4.2 Experimental and theoretical methods
        4.3 Results and discussion
        4.4 Summary
Chapter Five
    5 Temperature-induced phase transformation in Au_(55)Cu_(25)Si_(20) metallic liquid
        5.1 Introduction
        5.2 Experimental and theoretical methods
        5.3 Results and discussion
        5.4 Summary
Chapter Six
    6 Structural evolution of metallic liquids under pressure
        6.1 Introduction
        6.2 Computational details
        6.3 Results and discussion
        6.4 Summary
Chapter Seven
    7 Conclusions
Bibliography
List of Publications



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