Phase stability of Cu2Mg and CuMg2 compounds against noncrystallizations analyzed with a plastic crystal model

The phase stabilities of Cu2Mg and CuMg2 compounds were analyzed for their noncrystallizations with molecular dynamics (MD) simulations based on the plastic crystal model (PCM), which includes a series of processes for random rotations of hypothetical clusters around their centers of mass, relaxation and annealing. The calculation results in terms of pair-distribution functions reveal that the Cu2Mg alloy created with PCM tends to form in a crystalline structure, whereas the CuMg2 alloy forms in a noncrystalline structure. MD simulations based on PCM are validated because they are consistent with the experimental results indicating that the compositions for the Cu2Mg and CuMg2 alloys are outside and inside the amorphous-forming composition range (AFCR), respectively. PCM is of great importance due to its agreement with the experimental data on AFCR, which has yet to be obtained using conventional MD methods through quenching from a liquid phase.