How closely do many-body potentials describe the structure and dynamics of Cu-Zr glass-forming alloy?

KN Lad and N Jakse and A Pasturel, JOURNAL OF CHEMICAL PHYSICS, 146, 124502 (2017).

DOI: 10.1063/1.4979125

Molecular dynamics investigations of the structure and dynamics of Cu64.5Zr35.5 metallic glassforming alloy have been carried out using five different semi-empirical, many-body interaction potentials based on the Finnis-Sinclair model M. I. Mendelev et al., J. Appl. Phys. 102, 043501 (2007) (MSK); M. I. Mendelev et al., Philos. Mag. 89, 967 (2009) (MKOSYP); L. Ward et al., e-print arXiv: 1209.0619 (2012) (WAFW) and the embedded-atom model Y.Q. Cheng et al., Phys. Rev. Lett. 102, 245501 (2009) (CMS) and N. Jakse et al., Phys. Rev. B 85, 174201 (2012) (JNP). Although the total static structure factor of the alloy for all the five interaction potentials is, in general, found to be in good agreement with the experimental results, the investigation of a local structure in terms of icosahedral short-range order reveals that the effect of the interaction potential (especially the cohesive part) on the structure of the alloy is not as trivial as it seems. For MSK and JNP potentials, the self-intermediate scattering function F-s(q, t), q-dependence of the structural relaxation time T-alpha in the low-q region, and the self- diffusion coefficient, D-s, for Cu-atoms in the alloy are in excellent agreement with the experimental results. The results for MKOSYP, CMS, and WAFW potentials deviate significantly from the experiment and suggest the dynamics of the alloy to be faster. The difference in the description of the dynamics of the alloy by different potentials is found to be due to the difference in the relevant energy scales corresponding to the temperature scales. T-alpha and D-s exhibit Arrhenius temperature dependence in the high temperature regime above the melting temperature. We also suggest that the attractive forces influence the dynamics of the liquid alloy significantly, which is against the mere perturbative role assigned to the attractive forces in the van der Waals picture of liquids that has been challenged in the recent years. As the five interaction potentials are frequently employed to study thermodynamic, mechanical, and transport properties of Cu-Zr alloys, our study also provides a suitability check for these potentials. Published by AIP Publishing.

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