  In this paper we report on our theoretical studies of various aspects of the
correlated stopping power of two point-like ions (a dicluster) moving in close
but variable vicinity of each other in some metallic target materials the
latter being modelled by a degenerate electron gas with appropriate densities.
Within the linear response theory we have made a comprehensive investigation of
correlated stopping power, vicinage function and related quantities for a
diproton cluster in two metallic targets, aluminum and copper, and present
detailed and comparative results for three approximations to the electron gas
dielectric function, namely the plasmon-pole approximation without and with
dispersion as well as with the random phase approximation. The results are also
compared, wherever applicable, with those for an individual projectile.
