Pueblo Christopher E, Sun Minhua, Kelton K F
Department of Physics, Washington University, St Louis, Missouri 63130, USA.
Institute of Materials Science and Engineering, Washington University, St Louis, Missouri 63130, USA.
Nat Mater. 2017 Aug;16(8):792-796. doi: 10.1038/nmat4935. Epub 2017 Jul 10.
The dynamical behaviour of liquids is frequently characterized by the fragility, which can be defined from the temperature dependence of the shear viscosity, η (ref. ). For a strong liquid, the activation energy for η changes little with cooling towards the glass transition temperature, T. The change is much greater in fragile liquids, with the activation energy becoming very large near T. While fragility is widely recognized as an important concept-believed, for example, to play an important role in glass formation-the microscopic origin of fragility is poorly understood. Here, we present new experimental evidence showing that fragility reflects the strength of the repulsive part of the interatomic potential, which can be determined from the steepness of the pair distribution function near the hard-sphere cutoff. On the basis of an analysis of scattering data from ten different metallic alloy liquids, we show that stronger liquids have steeper repulsive potentials.
液体的动力学行为通常由脆性来表征，脆性可根据剪切黏度η对温度的依赖性来定义（参考文献 ）。对于强液体，η的活化能在冷却至玻璃化转变温度T的过程中变化很小。而在脆性液体中，这种变化要大得多，在T附近活化能会变得非常大。虽然脆性作为一个重要概念已被广泛认可——例如，人们认为它在玻璃形成过程中起重要作用——但其微观起源却知之甚少。在此，我们给出新的实验证据，表明脆性反映了原子间相互作用势中排斥部分的强度，这可由硬球截止附近对分布函数的陡度来确定。基于对十种不同金属合金液体散射数据的分析，我们表明，液体的排斥势越强，其脆性越大。
