ONE-STAGE CONTINUOUS MELTING TRANSITION IN 2 DIMENSIONS

Monte Carlo results are reported for melting of two-dimensional system s of N hard disks for various values of N. Runs of up to 10(8) Monte C arlo sweeps give the following equilibrium results: (1) there is a sin gle second-order transition at volume v(c) = 1.260 +/- 0.005; (2) the orientational order parameter drops discontinuously to zero at v = v(c ); (3) v(6) = 0.30 +/- 0.05 at v = v(c); (4) there is consistency with xi = exp(b/u(1/2)) in the isotropic phase, where u = v - v, and b sim ilar or equal to 0.8. An intermediate phase in which the volume can va ry by more than about 1% is ruled out.