Amorphous structures in the immiscible Ag-Ni system

Vapor quenching in the phase-separating Ag-Ni system creates alloys that ap pear homogeneously amorphous under conventional probes. However, an atomic- level structural analysis based on extended x-ray absorption fine structure s in combination with reverse Monte Carlo and molecular dynamics simulation s demonstrates that these new phases are characterized by nonuniform, spino dal-like structures on an extremely fine scale. This heterogeneous nature o f the structure is directly responsible for the unexpectedly low heat (and temperature) of crystallization observed in calorimetric measurements.