MOLECULAR-DYNAMICS CALCULATION FOR THE MODIFIED XY MODEL

In order to demonstrate the effectiveness of molecular dynamics (MD) for the determination of the density of states of a system that suffers an abrupt change of state, we have performed extensive calculations for the modified rotor model, defined by the interaction potential V(phi) = 2J{1 - [cos(phi/2)]p2} between neighboring rotors. Our results for 2-dimensional L x L lattices with L = 8, 16, 32, and 64 demonstrate clearly that the transition is continuous for p2 less-than-or-equal-to 24, but suggest a first-order transition for p2 greater-than-or-equal-to 28.