A locally preferred structure characterises all dynamical regimes of a supercooled liquid

R Soklaski and V Tran and Z Nussinov and KF Kelton and L Yang, PHILOSOPHICAL MAGAZINE, 96, 1212-1227 (2016).

DOI: 10.1080/14786435.2016.1158427

Recent experimental results suggest that metallic liquids universally exhibit a high-temperature dynamical crossover, which is correlated with the glass transition temperature (T-g). We demonstrate, using molecular dynamics results for Cu64Zr36, that this temperature, T-A approximate to 2 x T-g, is linked with cooperative atomic rearrangements that produce domains of connected icosahedra. Supercooling to a new characteristic temperature, T-D, is shown to produce higher order cooperative rearrangements amongst connected icosahedra, which manifests as the formation of large Zr-rich connected domains that possess macroscopic proportions of the liquid's icosahedra. This coincides with the decoupling of atomic diffusivities, largescale domain fluctuations and the onset of glassy dynamics in the liquid. These extensive domains then abruptly stabilise above T-g and eventually percolate before the glass is formed. All characteristic temperatures (T-A, T-D and T-g) are thus connected by successive manifestations of the structural cooperativity that begins at T-A.

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