SURFACE-DIFFUSION NEAR THE POINTS CORRESPONDING TO CONTINUOUS-PHASE TRANSITIONS

Employing the scaling arguments, we show that the temperature dependen ce of the chemical diffusion coefficient near the points corresponding to continuous phase transitions has power-law or inverse logarithmic singularities, D-c proportional to \Delta T\(alpha/(1 - alpha)) for al pha > 0, proportional to \Delta T\(-alpha) for alpha < 0, or proportio nal to 1/\1n\Delta T parallel to for alpha = 0, where alpha is the spe cific heat exponent. Monte Carlo simulations, executed with the parame ters corresponding to the O/W(110) system, indicate that these singula rities, occurring in a very narrow temperature interval, can be reprod uced only if the lattice size is large (L > 500). Outside the critical region, the temperature dependence of D-c is regular and the deviatio ns from the ideal Arrhenius behavior are relatively weak. In particula r, at appreciable coverages, the variations of the activation energy f or chemical diffusion are about 10 kJ/mol (this value amounts to appro ximate to 10% of the activation energy). (C) 1998 American Institute o f Physics. [S0021-9606(98)51132-4]