Two liquids of Al-Cu55 nanoalloys

2014.03.21 21:04

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 The development of short-to-medium-range order in atomic arrangements has generally been observed in noncrystalline solid systems such as metallic glasses. Whether such medium-range order (MRO) can exist in materials at well above their melting or glass-transition temperature has been a long-standing important scientific issue. Here, using ab initio molecular dynamics simulations, we show that a novel, persistent MRO exists in liquid Al-Cu alloys near the composition of CuAl3. The correlated atomic motions associated with the MRO give rise to a substantially enhanced viscosity in the vicinity of the composition. The component of the MRO liquid state gradually decreases with increasing temperature, and it disappears above a crossover temperature TLLC. The continuous liquid-liquid crossover through a percolationlike transition leads to a pronounced heat capacity peak at TLLC.


http://prl.aps.org/abstract/PRL/v108/i11/e115901

J. Kang et al, Phy. Rev. Lett. - Mar. 13, 2012