Strong correlation of atomic thermal motion in the first coordination shell of a Cu-Zr metallic glass

We demonstrate a strong correlation of atomic thermal motions in the first coordination shell of Cu50Zr50 metallic glass using molecular dynamics simulations, which explains directly the small thermal expansion coefficient calculated by the first maxima of pair correlation functions. The vibrational anisotropy in the glass is found to be even higher than in crystalline copper. The parallel-perpendicular anisotropy gradually decreases upon heating. The anisotropy in Zr-Zr is the strongest bonds among all the interatomic bonds, which is also very stable near the glass transition at 700 K. Structurally, the anisotropy can be correlated to Cu-centered (0 2 8 1) clusters. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4792752]