Dynamical structure factor of liquid Li, Na and Al

The dynamical structure factors, S(q, ω) of liquid lithium, sodium and aluminium have been studied near their melting points using Mori’s memory function formalism. The second order memory function was obtained by exploiting non-Markovian nature of the fourth order memory function and assuming that memory functions at their alternate stage have the same functional time dependence. We obtain an analytical expression for the second order memory function, whose form depends on wave number q. Results obtained for dynamical structure factor over a wide range of q values for liquid Na and Al have been found to be in good agreement with recent inelastic X-ray scattering experiments in contrast to the case of liquid Li. The behavior of non-Markovity parameter is also studied as a function of frequency, ω, at different values of q.