Adsorption of Dimer Molecules on Triangular and Honeycomb Lattices.

J. E. GONZÁLEZ; A. J. RAMIREZ-PASTOR; V. PEREYRA

LANGMUIR

Año: 2001 vol. 17 p. 6974 - 6980

0743-7463

Grand canonical Monte Carlo simulations have been used to study the adsorption of homonuclear dimers on triangular and honeycomb two-dimensional lattices. Adsorption isotherms, adsorption energy, differential heat of adsorption, and configurational entropy were calculated for attractive and repulsive nearestneighbor lateral interactions. In the second case (repulsive couplings) and low temperatures, we found two novel ordered phases in the adsorbate: (1) low-coverage ordered phase (LCOP), with 2/5 (5/9) of the sites occupied for a triangular (honeycomb) lattice; (2) high-coverage ordered phase (HCOP), with 2/3 of the sites filled for both lattices. The locations of the ordered phases are not symmetrical around õ ) 0.5; this is a consequence of the nonequivalence between vacancies and particles in the case of adsorption with multisite occupancy. The influence of the ordered structures on the thermodynamic quantities associated with the adsorbed monolayer has been analyzed and discussed in the context of the lattice-gas model.õ ) 0.5; this is a consequence of the nonequivalence between vacancies and particles in the case of adsorption with multisite occupancy. The influence of the ordered structures on the thermodynamic quantities associated with the adsorbed monolayer has been analyzed and discussed in the context of the lattice-gas model.-gas model.