第64回「非線形・統計力学とその周辺」セミナーのご案内

日時：平成１７年６月１０日（金）午後４時より

場所：京都大学工学部８号館３階共同５講義室

講演者：Prof. Per Arne Rikvold (Florida State University)

講演題目： DECAY OF METASTABLE NONEQUILIBRIUM PHASES, ENHANCED REACTION RATE, AND
DYNAMIC PHASE TRANSITION IN A MODEL OF CO OXIDATION WITH CO DESORPTION

講演要旨：

We present a computational study of the dynamic behavior of a
Ziff-Gulari-Barshad model of CO oxidation with CO desorption on a
catalytic surface. Our results indicate that below a critical desorption
rate the model exhibits a non-equilibrium, first-order phase transition
between low andi high CO coverage phases. Our kinetic Monte Carlo
simulations indicate that the transition process between these phases
follows a decay  mechanism very similar to the one described by the
classic Kolmorogov-Johnson-Mehl-Avrami theory of phase transformation by
nucleation and growth. We measure the lifetimes of the metastable phases on
each side of the transition line and find that they are strongly dependent
on the direction of the transformation, ie., from low to high coverage or
vice versa. Inspired by this asymmetry, we introduce a square-wave periodic
external forcing, whose two parameters can be tuned to enhance the
catalytic activity. At CO desorption rates below the critical value, we
find that this far-from-equilibrium system undergoes a dynamic phase
transition between a CO_2 productive phase and a nonproductive one.
In the space of the parameters of the periodic external forcing, this
nonequilibrium phase transition defines a line of critical points. The
maximum enhancement rate for the CO_2 production rate occurs near
this critical line.