A combination of experimental techniques and molecular-dynamics computer simulation is used to investigate the diffusion dynamics in ${\mathrm{Al}}_{80}{\mathrm{Ni}}_{20}$ melts. Experimentally, the self-diffusion coefficient of Ni is measured by the long-capillary (LC) method and by quasielastic neutron scattering. The LC method yields also the interdiffusion coefficient. Whereas the experiments were done in the normal liquid state, the simulations provided the determination of both self-diffusion and interdiffusion constants in the undercooled regime as well. The simulation results show good agreement with the experimental data. In the temperature range $3000\mathrm{K}⩾T⩾715\mathrm{K}$, the interdiffusion coefficient is larger than the self-diffusion constants. Furthermore, the simulation shows that this difference becomes larger in the undercooled regime. This result can be referred to a relatively strong temperature dependence of the thermodynamic factor $\Phi$, which describes the thermodynamic driving force for interdiffusion. The simulations also indicate that the Darken equation is a good approximation, even in the undercooled regime. This implies that dynamic cross correlations play a minor role for the temperature range under consideration.

• Received 9 February 2007

DOI:https://doi.org/10.1103/PhysRevB.75.174304