The defect-nucleated melting of Ar has been simulated by the gradual heating of lattices that contain voids using isobaric molecular dynamics. The criterion given by Solca [Chem. Phys. 224, 253 (1997)] has been used to determine the melting point from the transition temperature versus void size curve. A crystal containing a single void created by the removal of an atom and its nearest (n - 1) neighboring atoms was found to give almost the same melting temperature as a crystal containing n randomly distributed single-atom voids. The melting temperature is insensitive to the shape of the void. The critical void size, beyond which there is a sudden drop in the melting temperature, decreases with pressure. At various values of pressures ranging from 0.094 to 531.6 kbar the melting points are found to be in good agreement with the experimental results and with thermodynamic results using the same exp-6 potential. The results are consistent with the Lindemann criterion of melting and in better agreement with the Lindemann criterion than are the thermodynamic results. (C) 2003 American Institute of Physics.