Ryu Chae Woo, Egami Takeshi
Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee 37996, USA.
Materials Sciences and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
Phys Rev E. 2020 Oct;102(4-1):042615. doi: 10.1103/PhysRevE.102.042615.
Liquid fragility characterizes how steeply the viscosity of a glass-forming liquid decreases with increasing temperature above the glass transition. It is one of the most fundamental properties of a liquid, with high importance for science and application. Yet, its origin is unclear. Here we show that it is directly related to the structural coherence of the medium-range order (MRO) in liquid defined by the decay of the pair-distribution function with distance. The MRO can also be evaluated from the first peak of the structure function determined by x-ray or neutron diffraction, and it is a measure of the cooperativity of atomic motion in a diffusive event in supercooled liquids. These findings shed light on the mechanism of atomic transport in supercooled liquids.
液体脆性表征了玻璃形成液体的粘度在高于玻璃化转变温度时随温度升高而下降的陡峭程度。它是液体最基本的性质之一，对科学和应用具有高度重要性。然而，其起源尚不清楚。在这里，我们表明它与由对分布函数随距离衰减所定义的液体中程有序（MRO）的结构相干性直接相关。MRO也可以从由X射线或中子衍射确定的结构函数的第一个峰来评估，它是过冷液体中扩散事件中原子运动协同性的一种度量。这些发现揭示了过冷液体中原子传输的机制。
