Simulações entrópicas para um modelo tipo ZGB dependente da temperatura
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2019-04-04
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Universidade Federal de Goiás
Resumo
The ZGB model is a simple model built to describe some known steps of the CO−O2
reaction on a catalytic surface, which is represented in the model by a square lattice of
side L. The main events that occur are the adsorption of monoxide molecules CO and O2 oxygen at empty sites of the lattice, which occur, respectively, with probabilities y and
1−y . Another important event is the formation of a molecule of carbon dioxide CO2 , which occurs whenever a molecule of CO and an atom O are first neighbors adsorbed
in the lattice. Since an oxygen atom or a molecule of CO are adsorbed into the lattice,
they remain in the sites coming out only by reactions. We propose a catalytic system
saturated by CO molecules in order to
study the effect of temperature on the system and the oxidation of these species using
the rules of the model ZGB with small modifications. Attractive interactions between
adsorbed CO molecules and O atoms at the first neighboring sites and the desorption
phenomenon were taken into consideration. We consider the interaction CO-CO more
intense than O-O , so that the system energy is minimal when the entire lattice is filled
by CO molecules and is maximum when the lattice is empty or filled totally or partially
by not near-neighbors CO and O, being null its value for all these cases. We perform a
random walk in the energy space bounded by the interval above, calculating the density of states by means of entropic simulations. Once the state density is obtained, we calculate the partition function and the thermodynamic properties for a given temperature range by means of the canonical average. We found, through of a finite-size scale analysis, that our system suffers a first-order phase transition.
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SANTOS, E. D. Simulações entrópicas para um modelo tipo ZGB dependente da temperatura. 2019. 44 f. Dissertação (Mestrado em Fisica) - Universidade Federal de Goiás, Goiânia, 2019.