The formation of galaxy clusters in hierarchically clustering universes is investigated by means of high resolution N-body simulations .
The simulations are performed using a newly developed multi-mass scheme which combines a PM code with a high resolution N-body code .
Numerical effects due to time stepping and gravitational softening are investigated as well as the influence of the simulation box size and of the assumed boundary conditions .
Special emphasis is laid on the formation process and the influence of various cosmological parameters .
Cosmogonies with massive neutrinos are also considered .
Differences between clusters in the same cosmological model seem to dominate over differences due differing background cosmogony .
The cosmological model can alter the time evolution of cluster collapse , but the merging pattern remains fairly similar , e.g .
number of mergers and mass ratio of mergers .
The gross properties of a halo , such as its size and total angular momentum , also evolve in a similar manner for all cosmogonies and can be described using analytical models .
It is shown that the density distribution of a halo shows a characteristic radial dependence which follows a power law with a slope of \alpha = -1 at small and \alpha = -3 at large radii , independent of the background cosmogony or the considered redshift .
The shape of the density profiles follows the generic form proposed by Navarro et al .
( 1996 ) for all hierarchically clustering scenarios and retains very little information about the formation process or the cosmological model .
Only the central matter concentration of a halo is correlated to the formation time and therefore to the corresponding cosmogony .
We emphasise the role of non-radial motions of the halo particles in the evolution of the density profile .