Evidence of liquid-liquid transition in glass-forming La50Al35Ni15 melt above liquidus temperature.
Evidence of liquid-liquid transition in glass-forming La50Al35Ni15 melt above liquidus temperature.
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DOI：
10.1038/ncomms8696
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发表时间：
2015-07-13
影响因子：
16.6
通讯作者：
Wu Y
中科院分区：
文献类型：
--
作者：
Xu W;Sandor MT;Yu Y;Ke HB;Zhang HP;Li MZ;Wang WH;Liu L;Wu Y
液-液相变是一种液相向另一种具有相同组成的液相的相变，为研究液体结构与动力学之间的关系提供了关键机会。在这里，我们报告的实验证据的玻璃形成La 50 Al 35 Ni 15熔体的液相线温度以上的27 Al核磁共振，包括笼体积波动和原子扩散的温度依赖性的液-液转变。观察到的过冷度上的孵化时间的依赖性是一致的一阶相变。模拟结果表明，这种转变伴随着键取向顺序的变化，而没有显着的密度变化。原子扩散的温度依赖性也与实验结果一致。这些观测结果表明，在描述液体相变时需要二阶参数。 非密度驱动的液-液相变在理论上已经被预测，但直接的实验验证是具有挑战性的，因为液体往往在转变温度下保持亚稳态。在此，Xu等人提供了高于其液相线温度的镧基金属玻璃的证据。
Liquid–liquid transition, a phase transition of one liquid phase to another with the same composition, provides a key opportunity for investigating the relationship between liquid structures and dynamics. Here we report experimental evidences of a liquid–liquid transition in glass-forming La50Al35Ni15 melt above its liquidus temperature by 27Al nuclear magnetic resonance including the temperature dependence of cage volume fluctuations and atomic diffusion. The observed dependence of the incubation time on the degree of undercooling is consistent with a first-order phase transition. Simulation results indicate that such transition is accompanied by the change of bond-orientational order without noticeable change in density. The temperature dependence of atomic diffusion revealed by simulations is also in agreement with experiments. These observations indicate the need of two-order parameters in describing phase transitions of liquids. Non-density driven liquid-liquid transition has been predicted in theories, but direct experimental verification is challenging because liquid often remains metastable at transition temperature. Here, Xu et al. provide evidence in a lanthanum-based metallic glass above its liquidus temperature.