Nanoscale phase separation and local icosahedral order in amorphous alloysof immiscible elements - art. no. 144206

We demonstrate that local icosahedral ordering, as well as spinodal composi tional modulations with nanometer scale wavelengths, are characteristic of amorphous structures formed in an immiscible system with large positive hea t of mixing. This unique nature of the atomic-level structures allows the a morphous alloy to lower its enthalpy such that the heat of crystallization is of a magnitude comparable to that typically seen for amorphous phases in easy glass-forming systems. The development of such chemical decomposition and topological order in the short to medium range has been monitored in t he Ag-Ni model system using molecular dynamics (MD) simulations. The MD fin dings of the structural features and enthalpies, as well as their correlati on, are consistent with the experimental characterization results of vapor- deposited Ag-Ni amorphous phases.