Packings and defects of strongly coupled two-dimensional Coulomb clusters:Numerical simulation

The packings and defects of the strongly coupled two-dimensional Coulomb cl usters with particle number N from a few to a few hundred with different fo rms of mutual repulsion and central confining potentials at zero temperatur e are investigated using molecular-dynamics simulation through many anneali ng cycles. The circular symmetry of the confining potential and the interpl ay with the mutual repulsion lead to the strong competition between the out er circular shells and the inner triangular lattice. Generic packing behavi ors, such as the concentric shells with the classical periodic packing sequ ence at small N, and the triangular latticelike inner core surrounded by a few outer circular shells at large N are observed. The effects of changing the interaction and confining potentials on the detailed packing sequence, the radial variation of packing density, and the positions of the shell-tri angular core interface are investigated with a detailed study of the cluste r structures along with the formation and distribution of topological defec ts. [S1063-651X(99)03410-8].