Microscopic Modeling of Amorphization by Solid State Reactions: Role of Chemical Disorder and Elastic Softening in the Intermetallic Alloy NiZR₂

Abstract

We investigate the role played by chemical disorder in the phenomenon of solid state amorphization of the compound NiZr₂ by molecular dynamics simulations based on a realistic N-body potential. In addition we study the elastic response of the alloy upon introduction of an increasing number of antisite defects to monitor the possible occurrence of an elastic instabillty triggering the C-A (crystal-to-amorphous) transformation. Chemical disorder is proved to be a driving force of the C-A transformation as shown by the behavior of the structure factor calculated for different values of the long range order parameter S. A large elastic softening is recorded at the threshold value corresponding to amorphization and in this respect we are able to propose an original picture of solid state amorphization processes describing in a unified way the reaction to different forms of defects or impurities destabilizing the system.