An alternative method to characterize first- and second-order phase   transitions in surface reaction models
  In this work, we revisited the Ziff-Gulari-Barshad (ZGB) model to study its phase transitions and critical exponents through time-dependent Monte Carlo simulations. We used a method proposed recently to locate the non-equilibrium second-order phase transitions and that has been successfully used in systems with defined Hamiltonians and with absorbing states. This method, which is based on optimization of the coefficient of determination of the order parameter, was able to characterize the second-order phase transition of the model, as well as its upper spinodal point, a pseudo-critical point located near the first-order transition. The static critical exponents $\beta $, $\nu_{\parallel }$, and $\nu_{\perp }$, as well as the dynamic critical exponents $\theta $ and $z$ for the second-order point were also estimated and are in excellent agreement with results found in literature. 
Henrique A. Fernandes, Roberto da Silva, Eder D. Santos, Paulo F.   Gomes, Everaldo Arashiro
cond-mat.stat-mech