The Tersoff empirical potential for GaN has been developed in this study. With this model, structural and thermodynamic properties of zincblende GaN have been calculated through molecular-dynamics simulations. The calculated bulk properties and elastic constants are in agreement with experimental and theoretical results. Thermal expansion, specific heat, Debye temperature and melting temperature have also been investigated. These results show the reliability of the Tersoff potential to investigate physical properties of Ga N systems.