  The formation, inner properties, and spatial distribution of galaxy groups
and clusters are closely related to the background cosmological model. We use
numerical simulations of variants of the CDM model with different cosmological
parameters and distinguish relaxed objects from recent mergers using the degree
of virialisation. Mergers occur mostly in deep potential wells and mark the
most important structure formation processes. As consequence, the
autocorrelation function of merged halos has a higher amplitude and is steeper
than that of the virialized clusters. This can be directly connected to the
same result found from the observation of luminous infrared galaxies; they are
as well more strongly correlated and can primarily be identified with ongoing
merging events.
