Critical behavior of repulsive linear k-mers on triangular lattices

P. M. PASINETTI; F. ROMÁ; J. L. RICCARDO; A. J. RAMIREZ-PASTOR

PHYSICAL REVIEW B - CONDENSED MATTER AND MATERIALS PHYSICS

The American Physical Society

Lugar: USA; Año: 2006 vol. 74 p. 155418 - 155425

0163-1829

Monte Carlo (MC) simulations and finite-size scaling analysis have been carried out to study the critical behavior in a submonolayer two-dimensional gas of repulsive linear k-mers on a triangular lattice at coverage k/(2k+1). A low-temperature ordered phase, characterized by a repetition of alternating files of adsorbed k-mers separated by k+1 adjacent empty sites, is separated from the disordered state by an order-disorder phase transition occurring at a finite critical temperature, Tc. The MC technique was combined with the recently reported free-energy minimization criterion approach (FEMCA) [F. Romá et al., Phys. Rev. B 68, 205407 (2003)] to predict the dependence of the critical temperature of the order-disorder transformation. The dependence on k of the transition temperature, Tc(k), observed in MC is in qualitative agreement with FEMCA. In addition, an accurate determination of the critical exponents has been obtained for adsorbate sizes ranging between k=1 and 3. For k>1, the results reveal that the system does not belong to the universality class of the two-dimensional Potts model with q=3 (k=1, monomers). Based on symmetry concepts, we suggested that the behavior observed for k=1, 2, and 3 could be generalized to include larger particle sizes (k ³ 2).