  It is shown that the solution of generalized Langevin equation can be
obtained on the basis of simple comparison of the time scale for the velocity
autocorrelation function of a particle (atom, molecule) and of the time scale
for the corresponding memory function. The result expression for the velocity
autocorrelation function contains dependence on the non-Markovity parameter,
which allows one to take into account memory effects of the investigated
phenomena. It is demonstrated for the cases of liquid tin and liquid lithium
that the obtained expression for the velocity autocorrelation function is in a
good agreement with the molecular dynamics simulation results.
