Interfacial colloidal crystals and melting transition

Polystyrene spheres (diameter approximately 3000 AA) trapped at the air-water interface and interacting via dipole-dipole repulsion have been seen to form a two-dimensional triangular lattice. The authors report the first molecular dynamics study of such an interfacial colloidal crystal. It is shown that the system undergoes a first-order melting transition in the region Gamma =59-65, where Gamma is the ratio of the average potential to kinetic energy. The transition entropy per particle is 0.3 kB.