Potts model with $q=4,6,$ and 8 states on Voronoi-Delaunay random lattice

Through Monte Carlo simulations we study two-dimensional Potts models with $q=4, 6$ and 8 states on Voronoi-Delaunay random lattice. In this study, we assume that the coupling factor $J$ varies with the distance $r$ between the first neighbors as $J(r)propto e^{-a r}$, with $a geq 0$ . The disordered system is simulated applying the singler-cluster Monte Carlo update algorithm and reweigting technique. In this model both second-order and first-order phase transition are present depending of $q$ values and $a$ parameter. The critical exponents ratio $beta/ u$, $gamma/ u$, and $1/ u$ were calculated for case where the second-order phase transition are present. In the Potts model with $q=8$ we also studied the distribution of clusters sizes.