  A combination of experimental techniques and molecular dynamics (MD) computer
simulation is used to investigate the diffusion dynamics in Al80Ni20 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 K >= T >= 715 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
refered 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.
