Issue
EPL
Volume 85, Number 3, February 2009
Article Number 30004
Number of page(s) 6
Section General
DOI http://dx.doi.org/10.1209/0295-5075/85/30004
Published online 03 February 2009
EPL, 85 (2009) 30004
DOI: 10.1209/0295-5075/85/30004

Numerical study of the evaporation/condensation phase transition of droplets for an irreversible reaction model

E. 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

yasser.loscar@gmail.com

received 7 November 2008; accepted in final form 7 January 2009; published February 2009
published online 3 February 2009

Abstract
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$\hbox{--} $ 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.

PACS
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.

© EPLA 2009