Local atomic structure in equilibrium and supercooled liquid Zr75.5Pd24.5

Atomic structures were obtained in equilibrium and supercooled eutectic Zr75.5Pd24.5 liquids by in situ high-energy synchrotron diffraction measurements using the beamline electrostatic levitation (BESL) technique, which provides a high-vacuum, containerless, environment. Reverse Monte Carlo fits to the x-ray static structure factors, constrained using partial pair correlation functions obtained from ab initio molecular dynamics simulations, indicate the presence of medium-range order (MRO) in the form of a strong tendency for Pd-Pd (solute-solute) avoidance. This order persists over the entire temperature range studied, from 170 degrees C above the equilibrium liquidus temperature to 263 degrees C below it. Further, a quantitative analysis of the atomic structures obtained indicates a modest degree of icosahedral-like local order around Pd atoms, with the clusters showing an increased tendency for face-sharing to form more extended structures with decreasing temperature. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4737381]