Lattice gas model for fragmentation and phase transition in nuclear collisions

We introduce a lattice gas model to provide a unified description of nuclear equation of state and fragmentations. The nuclear equation of state is evaluated in Bragg-Williams as well as in Bethe-Peierls approximations. The model shows a liquid-gas type phase transition, similar to the characteristics of a mean field theory with Skyrme interactions. Nuclear fragmentations are investigated for different densities at finite temperatures. Power law behavior for fragments is observed at critical point. Studies of fragment distribution and the second moment S2 show that the thermal critical point coincides with the percolation point at the critical density. High temperature behavior of the model shows characteristics of chemical equilibrium. The molecular dynamics calculation for disassembly is carried out to include the Coulomb interaction in heavy ion collisions. The model reproduces the characteristics of the fragmentation data for both Ar-Sc and Au-Au collisions