Numerical study of the evaporation/condensation phase transition of droplets for an irreversible reaction modelE. S. Loscar and E. V. Albano
Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), CCT La Plata CONICET, UNLP-Sucursal 4 - Casilla de Correo 16, (1900) La Plata, Argentina
received 7 November 2008; accepted in final form 7 January 2009; published February 2009
published online 3 February 2009
The ZGB model (ZIFF M. R., GULARI E. and BARSHAD Y., Phys. Rev. Lett., 56 (1986) 2553) for a monomer-dimer catalytic reaction exhibits both second-order and first-order irreversible phase transitions. We report a numerical simulation study of the ZGB model close to coexistence, performed by using the constant-coverage monomer ensemble (CC). By means of CC stationary measurements we found that, in the super-saturated region, there is a phase-transition like behaviour, for finite systems, between a super-saturated state and a phase where solid monomer droplets coexist with the super-saturated state. Also, we show that the transition point converges, according to a power law behaviour, towards coexistence, so that it is no longer possible to measure any (thermodynamic) spinodal point by using the CC stationary approach. However, by using a dynamic CC ensemble, evidence of the upper spinodal point can clearly be identified: scale invariance of the monomer-droplet size distribution and a maximum in the susceptibility. It is also discussed how to define a spinodal point in the thermodynamic limit for this model.
05.70.Fh - Phase transitions: general studies.
64.60.De - Statistical mechanics of model systems (Ising model, Potts model, field-theory models, Monte Carlo techniques, etc.).
82.65.+r - Surface and interface chemistry; heterogeneous catalysis at surfaces.
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