Power-law scaling and fractal nature of medium-range order in metallic glasses
Power-law scaling and fractal nature of medium-range order in metallic glasses
复制标题
DOI：
10.1038/nmat2340
复制
发表时间：
2009-01-01
期刊：
影响因子：
41.2
通讯作者：
Wang, X. -L.
中科院分区：
文献类型：
--
作者：
Ma, D.;Stoica, A. D.;Wang, X. -L.
金属玻璃的原子结构一直是一个长期存在的科学问题。与晶体金属不同的是，晶体金属的长程顺序是通过被称为单元格的基本构建块的周期性堆叠建立起来的，金属玻璃没有长程平移或定向顺序，尽管存在一定程度的中短期顺序（1-3）。先前的研究（1-4）已经确定溶质（少数原子）为中心的团簇是金属玻璃中短距离有序的基本组成部分。已经提出了理想的团簇填充方案，如立方晶格(1)和准晶体中的二十面体(3)上的有效团簇填充，并首次提供了对金属玻璃中程有序的见解。然而，这些包装方案打破了几个集群的长度尺度。本文在中子和x射线衍射实验的基础上，提出了一种新的原子簇自相似填充方案。结果表明，中量程序列具有维数为2.31的分形网络特征，并在中量程长度尺度上用幂律相关函数来描述。我们的发现为无序材料的有序提供了一个新的视角，并对理解它们的结构-性质关系具有广泛的意义，特别是那些涉及长度尺度变化的材料。
The atomic structure of metallic glasses has been a long-standing scientific problem. Unlike crystalline metals, where long-range ordering is established by periodic stacking of fundamental building blocks known as unit cells, a metallic glass has no long-range translational or orientational order, although some degrees of short- and medium-range order do exist(1-3). Previous studies(1-4) have identified solute- (minority atom)-centred clusters as the fundamental building blocks or short- range order in metallic glasses. Idealized cluster packing schemes, such as efficient cluster packing on a cubic lattice(1) and icosahedral packing(3) as in a quasicrystal, have been proposed and provided first insights on the medium-range order in metallic glasses. However, these packing schemes break down beyond a length scale of a few clusters. Here, on the basis of neutron and X-ray diffraction experiments, we propose a new packing scheme - self-similar packing of atomic clusters. We show that the medium-range order has the characteristics of a fractal network with a dimension of 2.31, and is described by a power-law correlation function over the medium-range length scale. Our finding provides a new perspective of order in disordered materials and has broad implications for understanding their structure-property relationship, particularly those involving a change in length scales.