Effect of Random Disorder on the Monomer-Dimer Reaction Model.

E. S. LOSCAR; E. V. ALBANO

Mar del Plata. Buenos Aires, Argentina.

Congreso; XV Conference on Nonequilibrium Statistical Mechanics and Nonlinear Physics (Medyfinol' 06); 2006

Statistical and nonlinear physics community in Latin-America.

Among the many lattice models used for describing nonequilibrium phase transitions on surface heterogeneous catalysis, the monomer-dimer reaction model known as ZGB is well-known for capturing some of the complexity of the phenomena [1]. In ZGB, the single continuous parameter is the partial pressure of monomers. Working on homogeneous substrates, this simple model shows a continuous irreversible phase transition in the directed percolation class (low pressures) and a discontinuous first order phase transition (high pressures). In this work we study the influence of an inhomogeneous substrate on these basic phenomena. Quenched disorder--measured by the concentration of non-active sites (Xd)--is introduced in the substrate in the form of random dilution. The epidemic analysis shows that disorder generates a logarithmic (instead of the power law behavior seen for pure ZGB) time dependence on the characteristic dynamical quantities. Furthermore, the static exponents depend on Xd, and are therefore not universal. Above a threshold in the amount of disorder (XdC ~ 0.05), the first order transition is changed to a continuous one with a critical behavior similar to the transition seen at low pressure. References [1] Ziff R.M., Gulari E. and Barshad Y. Phys. Rev. Lett. 56, 487 (1986).