EVIDENCE FOR STRUCTURAL EFFECTS IN SELF-DIFFUSION

Atomic self-motion in liquid lead was studied on the molecular dynamics model of 16 384 particles using the effective pair potential which was derived earlier from the measured structure factor. The simulation was carried out at two temperatures, 623 and 1170 K, the former being close to the melting point. At 623 K, the deviation of the incoherent intermediate-scattering function F(s) (Q,t) from its Langevin approximation, for long enough times, was found to display a characteristic pattern of Q dependence which resembles that of the static structure factor S(Q). Some elements of this picture of Q dependence were also found in the high-temperature region. These results indicate that sizable effects of coupling between the diffusion process and the structural relaxation, known to be characteristic of supercooled-liquid dynamics, are well defined in the normal-liquid domain and they may be found even in the temperature region well above the melting point.