Structure of the glass-forming metallic liquids by ab-initio and classical molecular dynamics, a case study: quenching the Cu60Ti20Zr20 alloy

摘要

We consider the question of the amorphization of metallic alloys by meltquenching, as predicted by molecular dynamics simulations with semi-empiricalpotentials. The parametrization of the potentials is discussed on the exampleof the ternary Cu-Ti-Zr transition metals alloy, using as reference theab-initio simulation. The pair structure in the amorphous state is computedfrom a potential of the Stillinger Weber form. The transferability of theparameters during the quench is investigated using two parametrizations: fromsolid state data, as usual, and from a new parametrization on the liquidstructure. When the adjustment is made on the pair structure of the liquid, asatisfactory transferability is found between the pure components and theiralloys. The liquid structure predicted in this way agrees well with experiment,in contrast with the one obtained using the adjustment on the solid. The finalstructure, after quenches down to the amorphous state, determined with the newset of parameters is shown to be very close to the ab-initio one, the latterbeing in excellent agreement with recent X-rays diffraction experiments. Thecorresponding critical temperature of the glass transition is estimated fromthe behavior of the heat capacity. Discussion of the consistency between thestructures predicted using semi-empirical potentials and ab-initio simulation,and comparison of different experimental data underlines the question of thedependence of the final structure on the thermodynamic path followed to reachthe amorphous state.