Frank Stefan, Roberts Daniel E, Rikvold Per Arne
Department of Physics, Center for Materials Research and Technology, and School of Computational Science, Florida State University, Tallahassee, Florida 32306-4350, USA.
J Chem Phys. 2005 Feb 8;122(6):064705. doi: 10.1063/1.1847653.
The influence of nearest-neighbor diffusion on the decay of a metastable low-coverage phase (monolayer adsorption) in a square lattice-gas model of electrochemical metal deposition is investigated by kinetic Monte Carlo simulations. The phase-transformation dynamics are compared to the well-established Kolmogorov-Johnson-Mehl-Avrami theory. The phase transformation is accelerated by diffusion, but remains in accord with the theory for continuous nucleation up to moderate diffusion rates. At very high diffusion rates the phase-transformation kinetic shows a crossover to instantaneous nucleation. Then, the probability of medium-sized clusters is reduced in favor of large clusters. Upon reversal of the supersaturation, the adsorbate desorbs, but large clusters still tend to grow during the initial stages of desorption. Calculation of the free energy of subcritical clusters by enumeration of lattice animals yields a quasiequilibrium distribution which is in reasonable agreement with the simulation results. This is an improvement relative to classical droplet theory, which fails to describe the distributions, since the macroscopic surface tension is a bad approximation for small clusters.
通过动力学蒙特卡罗模拟，研究了最近邻扩散对电化学金属沉积方形晶格气体模型中亚稳态低覆盖相（单层吸附）衰减的影响。将相变动力学与成熟的柯尔莫哥洛夫-约翰逊-梅尔-阿夫拉米理论进行了比较。扩散加速了相变，但在中等扩散速率以下，相变仍符合连续成核理论。在非常高的扩散速率下，相变动力学表现出向瞬时成核的转变。然后，中等尺寸团簇的概率降低，有利于大团簇的形成。当过饱和度反转时，吸附质解吸，但在解吸的初始阶段，大团簇仍倾向于生长。通过枚举晶格动物来计算亚临界团簇的自由能，得到了一种准平衡分布，该分布与模拟结果合理吻合。这相对于经典液滴理论是一种改进，经典液滴理论无法描述这些分布，因为宏观表面张力对于小团簇来说是一个很差的近似。
