Surface phase transitions in one-dimensional channels arranged in a triangular cross-sectional structure: Theory and Monte carlo simulation

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

JOURNAL OF CHEMICAL PHYSICS

AMER INST PHYSICS

Año: 2006 p. 214705 - 214713

0021-9606

Monte Carlo simulations and finite-size scaling analysis have been carried out to study the criticalbehavior in a submonolayer lattice-gas of interacting monomers adsorbed on one-dimensionalchannels arranged in a triangular cross-sectional structure. Two kinds of lateral interaction energieshave been considered: 1 wL, interaction energy between nearest-neighbor particles adsorbed alonga single channel and 2 wT, interaction energy between particles adsorbed across nearest-neighborchannels. We focus on the case of repulsive transverse interactions wT0, where a rich variety ofstructural orderings are observed in the adlayer, depending on the value of the parameters kBT/wTbeing kB the Boltzmann constant and wL /wT. For wL /wT= 0, successive planes are uncorrelated,the system is equivalent to the triangular lattice, and the well-known 33 33 * ordered phase is found at low temperatures and a coverage, , of 1/ 3 2/3. In the more general case wL /wT0, a competition between interactions along a single channel and a transverse coupling between sites in neighboring channels leads to a three-dimensional adsorbed layer. Consequently, the 33 and 33 * structures “propagate” along the channels and new ordered phasesappear in the adlayer. Each ordered phase is separated from the disordered state by a continuousorder-disorder phase transition occurring at a critical temperature, Tc, which presents an interestingdependence with wL /wT. The Monte Carlo technique was combined with the recently reported freeenergy minimization criterion approach FEMCA F. Romá et al., Phys. Rev. B 68, 205407 2003to predict the critical temperatures of the order-disorder transformation. The excellent qualitativeagreement between simulated data and FEMCA results allows us to interpret the physical meaningof the mechanisms underlying the observed transitions