REVERSE MONTE-CARLO STUDY OF STRUCTURE CHANGES IN AMORPHOUS PD52NI32P16 UPON ANNEALING

Structure changes in amorphous Pd52Ni32P16 upon relaxation were modele d by means of reverse Monte Carlo (RMC) simulations using neutron-diff raction data from M. Schaal, P. Lamparter, and S. Steeb [Z. Naturforsc h. Teil A 43, 1055 (1988)] as input for the RMC program. Two states af ter annealing (2 h at 570 K and 2 h at 607 K) and the as-quenched stat e were successfully modeled. The resulting three-dimensional models of the structure were inspected for changes in the nearest-neighbor coor dinations (short-range order) and for changes at-larger interatomic di stances (medium-range order) upon relaxation. It was found that the sh ort-range order is affected by annealing, resulting in, for instance, a sharpening of the Voronoi volume distribution. These results were fo und to agree with interpretations of experimental atomic mobility stud ies. The effect of annealing on multibody correlation functions for me dium-range distances is much less pronounced than that for the short-r ange distances, and the two appear to be largely decoupled from one an other. These results, together with the observed annealing effect on t he decay rate of the peaks of the reduced radial distribution function , suggest that medium-range ordering is not merely a reflection of sho rt-range ordering, but has its origin in a change in propagation of di sorder in the structure. Medium-range ordering can therefore be treate d as a separate effect of annealing.