MELTING OF 2-DIMENSIONAL COLLOIDAL CRYSTALS - A SIMULATION STUDY OF THE YUKAWA SYSTEM

The two-dimensional melting transition of charged polystyrene spheres in aqueous colloidal suspension has been studied by molecular dynamics simulation of a screened Coulomb system. Some central predictions of the Kosterlitz-Thouless-Halperin-Nelson-Young theory of defect-mediate d melting are confirmed, such as an apparent divergence of the correla tion lengths for translational and bond-orientational order at differe nt thermodynamic state points, but there are also predictions of the t heory that are violated. The defect topology is very complex, with osc illation periods of the defect density of many million time steps dura tion. The need for extensive sampling and, to a lesser degree, the cho ice of potential function continue to be the crucial issues for any at tempt to generate a hexatic structure by means of computer simulation.