Phase transitions and thermodynamic properties of the antiferromagnetic q=5 clock model on a triangular lattice with second-nearest-neighbor interactions

The phase transitions, magnetic structures of the ground state, and thermodynamic properties of a q= 5 antiferromagnetic Potts model on a triangular lattice with exchange interactions of first-J1 and second-nearest neighbors J2 are studied by the Monte Carlo method. Computations are carried out in the range of the second-neighbor-exchange interaction values-2.4 <= J(2) <= 0.0 with fixed J(1)= -1. The magnetic structures for the ground state in the addressed interval are derived. A phase diagram of the critical temperature versus the second-nearest-neighbor interaction value is plotted. The antiferromagnetic interactions of second-neighbors are found to result in a change of a second-order phase transition to a first-order one.