It was recalled that 2-dimensional solids which were made up of particles with short-range attractions exhibited a solid-solid critical point. Computer simulations were performed which showed that, when near to this point, the crystal became unstable to dislocation unbinding. Since the concentration of free dislocations was very small, the resultant phase was expected to be a stable hexatic one. It was suggested that such hexatic phases near to a solid-solid critical point could be observed experimentally in confined colloidal suspensions. It was stressed that the results were not particularly sensitive to the form of the potential. That is, any sufficiently short-range potential was expected to induce a solid-solid transition and hence a finite region of hexatic phase in the neighborhood of the critical point. The hexatic phase formed due to density fluctuations which occurred in the neighborhood of the solid-solid critical point, rather than long-wavelength shear modes which were introduced by the proximity of the liquid/solid melting line. The regions of hexatic phase increased in extent as the range of the potential was increased. When sufficiently close to the point where the low-density solid phase became unstable, hexatic regions could extend as far as the melting line. The high density of the hexatic regions which were investigated resulted in a very low defect density. This prevented direct observation of the power-law decay of bond orientational correlation functions during the present simulations.

Dislocation Unbinding in Dense Two-Dimensional Crystals. P.Bladon, D.Frenkel: Physical Review Letters, 1995, 74[13], 2519-22