  We give evidence that particles interacting via the simple, radially
symmetric square-shoulder potential can self-organize in highly complex,
low-symmetry lattices, forming thereby clusters, columns, or lamellae; only at
high pressure compact, high-symmetry structures are observed. Our search for
these ordered equilibrium structures is based on ideas of genetic algorithms, a
strategy that is characterized by a high success rate. A simple mean-field type
consideration complements these findings and locates in a semi-quantitative way
the cross-over between the competing structures.
