Molecular Dynamics Simulation on a Glassforming NiZr- System: Diffusion Coefficients and Critical Temperature

TL;DR

This study uses molecular dynamics simulations to analyze diffusion coefficients and critical temperature in a NiZr glassforming system, applying mode-coupling theory to interpret the temperature dependence of atomic diffusion.

Contribution

It provides the first detailed MD simulation analysis of diffusion and critical temperature in NiZr, using first-principles-based potentials and mode-coupling theory.

Findings

Critical temperature Tc ~ 950 K identified.

Diffusion coefficients follow a power-law near Tc.

Different gamma exponents for Ni and Zr atoms.

Abstract

The diffusion coefficients of Ni DNi and Zr DZr, and also the critical temperature Tc of the system, as results of data analysis from Molecular Dynamics (MD) Simulation, are presented. An NpT-Ensemble of 648 atoms is simulated in a Box with L ~ 26,2 Angstrom by using Stillinger-Weber potential model with adopting paramaters for NiZr-System that based on results of first-principle electron teori from Hausleitner and Hafner. The present simulations are carried out by numerically integrating the Newtonian equation of atoms, and for integrating a fifth order predictor- corrector algorithm is used with time step dt = 2.5 10-15 s. Then diffusion coefficients and a critical temperature Tc are analyzed qualitatively on the basis of mode- coupling theory (MCT) for glass transition (GT). One of MCT-predictions is that temperature dependence of Diffusion coefficients follows a power-law with non- universal exponent parameter gamma, namely Di ~|T-Tc|^gamma From analysis results it is found that Tc ~ 950 K with gamma ~ 1.8 for Ni-atom and gamma ~ 2.0 for Zr-atom.