INIFTA   05425
INSTITUTO DE INVESTIGACIONES FISICO-QUIMICAS TEORICAS Y APLICADAS
Unidad Ejecutora - UE
artículos
Título:
Dynamic Response of Silver Monolayers Adsorbed on Gold(100) upon an Oscillatory Variation of the Chemical Potential: A Monte Carlo Simulation Study.
Autor/es:
CECILIA GIMÉNEZ, M; EZEQUIEL V ALBANO
Revista:
J Phys Chem C
Editorial:
American Chemical Society
Referencias:
Lugar: Washington; Año: 2007 vol. 111 p. 1809 - 1815
Resumen:
On the basis that the
underpotential electrochemical deposition of Ag atoms on the Au(100) surface
exhibits sharp first-order phase transitions at well-defined values of the
(coexistence) chemical potential (coex), we performed extensive
simulations aimed at investigating the hysteretic dynamic behavior of the
system close to coexistence upon the application of a periodic signal of the
form (t) = coex + o sin(2t/), where o and are the amplitude and the period of the
sweep, respectively. For relatively short periods and small enough amplitudes,
the system becomes trapped either at low or high Ag coverage states, as shown
by recording hysteresis loops. This scenario is identified as dynamically
ordered states (DOS) such that the relaxation time (relax) of the corresponding
metastable state obeys relax > . On the other hand, by properly increasing o and/or , one finds that the Ag coverage gently
follows the external drive (here relax < ) and the system is said to enter into
dynamically disordered states (DDS), where hysteresis loops show almost
symmetric limiting cycles. This symmetry breaking between limiting cycles
driven by an external signal is discussed in terms of the concept of
(out-of-equilibrium) dynamic phase transitions between DOS and DDS, similar to
those encountered when a magnetic system is placed in the presence of a variable
external magnetic field. However, a careful finite-size scaling study reveals
that at least at T = 300 K the Ag/Au(100) system does not exhibit true
second-order phase transitions but rather a crossover behavior between states.
A diagram showing the location of the ordered and disordered states in the versus plane is obtained and discussed.