Stokes-Einstein relation and excess entropy in Al-rich Al-Cu melts

A Pasturel (1) , N Jakse (1)

1 SIMaP - Science et Ingénierie des Matériaux et Procédés

We investigate the conditions for the validity of the Stokes-Einstein relation that connects diffusivity to viscosity in melts using entropy-scaling relationships developed by Rosenfeld. Employing ab initio molecular dynamics simulations to determine transport and structural properties of liquid Al-1 Cu--x(x) alloys (with composition x <= 0.4), we first show that reduced self-diffusion coefficients and viscosities, according to Rosenfeld's formulation, scale with the two-body approximation of the excess entropy except the reduced viscosity for x = 0.4. Then, we use our findings to evidence that the Stokes-Einstein relation using effective atomic radii is not valid in these alloys while its validity can be related to the temperature dependence of the partial pair-excess entropies of both components. Finally, we derive a relation between the ratio of the self-diffusivities of the components and the ratio of their pair excess

Domaines: Matériaux

A Pasturel, N Jakse. Stokes-Einstein relation and excess entropy in Al-rich Al-Cu melts. Applied Physics Letters, 2016, 109 (4), pp.5. ⟨10.1063/1.4960015⟩. ⟨hal-01463949⟩