The diamond melting line was determined for a model system based on Brenner＇s bond order potential for hydrocarbon systems. The location of this first-order phase boundary was found by a free energy calculation of the diamond and liquid phases, using atomistic simulation methods. The melting line was found to have a positive slope consistent with the present understanding. The location at lower pressure was also consistent with experiment and a number of other theoretical approaches. The slope is found to increase with pressure. The structure of the liquid is examined as a function of density and is suggestive of a Liquid-liquid phase boundary.