Atomic structure and transport properties of Cu50Zr45Al5 metallic liquids and glasses: Molecular dynamics simulations

We have simulated the atomic structure and the transport properties of Cu50Zr45Al5 metallic liquids and glasses within a wide cooling temperature range from 2000 to 300 K, using molecular dynamics simulations. High fractions of Cu- and Al-centered full icosahedra and Zr-centered icosahedra-like clusters have been detected in both supercooled liquids and glasses. The heat capacity and linear thermal expansion coefficients of both liquids and glasses are also calculated, which have not been reported for this off-eutectic composition previously. The critical temperature (T-c) of Cu50Zr45Al5 liquids is determined to be 874.7 K by investigating the self-diffusivity using the mode coupling theory. A dynamics cross-over is detected in the vicinity of T-c, which can be reflected by different diffusion mechanisms and a remarkable deviation from the Einstein-Stokes relation. The results further suggest a fragile to strong transition of Cu50Zr45Al5 liquids between 1500 K and 1300 K upon cooling, which may result from a drastic increase of stable clusters within this temperature range. (C) 2011 American Institute of Physics. [doi:10.1063/1.3658252]