Hierarchical densification and negative thermal expansion in Ce-based metallic glass under high pressure
Hierarchical densification and negative thermal expansion in Ce-based metallic glass under high pressure
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DOI：
10.1038/ncomms6703
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发表时间：
2015-02
影响因子：
16.6
通讯作者：
Q. Luo;G. Garbarino;B. Sun;D. Fan;Yue Zhang;Zhi Wang;Yajuan Sun;J. Jiao;Xiaodong Li;Pengshan Li;N. Mattern;J. Eckert;Jun Shen
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文献类型：
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作者：
Q. Luo;G. Garbarino;B. Sun;D. Fan;Yue Zhang;Zhi Wang;Yajuan Sun;J. Jiao;Xiaodong Li;Pengshan Li;N. Mattern;J. Eckert;Jun Shen
非晶材料的多晶性是凝聚态物理中最令人感兴趣的研究课题之一。在非晶态金属中，多晶转变的性质知之甚少。在这里，我们调查的Ce基金属玻璃（MG）的结构演变与压力在室温（RT）和玻璃化转变温度附近的同步辐射X射线衍射，揭示新的行为。MG示出在两个温度下的分层致密化过程，所产生的原子间相互作用的层次结构。与连续和平滑的低密度到中等密度的非晶态转变在RT的过程相比，一个相对突然和不连续的转变在5.5 GPa附近观察到在390 K，这表明可能是一个弱的一阶性质。此外，在不同的压力窗口中观察到的中程有序的正和异常-负的热膨胀行为，这可能与低能振动运动和松弛的弱连接溶质中心的集群。
The polyamorphsim in amorphous materials is one of the most fascinating topics in condensed matter physics. In amorphous metals, the nature of polyamorphic transformation is poorly understood. Here we investigate the structural evolution of a Ce-based metallic glass (MG) with pressure at room temperature (RT) and near the glass transition temperature by synchrotron X-ray diffraction, uncovering novel behaviours. The MG shows hierarchical densification processes at both temperatures, arising from the hierarchy of interatomic interactions. In contrast with a continuous and smooth process for the low- to medium-density amorphous state transformation at RT, a relatively abrupt and discontinuous transformation around 5.5 GPa is observed at 390 K, suggesting a possible weak first-order nature. Furthermore, both positive and abnormal-negative thermal expansion behaviours on medium-range order are observed in different pressure windows, which could be related to the low-energy vibrational motions and relaxation of the weakly linked solute-centred clusters.