Nucleation barrierless

For a > 1, nucleation is barrierless—i.e., the transformation is controlled solely by growth kinetics. However, for a < 1, a barrier exists. The local minimum of AQ (r) at point A in the plot corresponds to a metastable cylinder of /3 of radius r0 forming along the dislocation line. (In a sense, this is analogous to the Cottrell atmosphere described in Section 3.5.2.) In Eq. 19.54, the metastable cylinder s radius is... 

Monatomic steps at real surfaces do significantly influence not only the nucleation act, but also the spreading and overlapping of 2D islands, which determine the shape of potentiostatic current transients. Neglecting the adsorptive contribution in eq. (3.64), i.e., ep Qcd, and assuming a barrierless nucleation and growth of a condensed 2D Mcads phase only at steps with a regular pattern characterized by a... 

FIGURE 1.3 Rate of nucleation at different densities (or supersaturation) at T = 0.741 and N = 500 in the NVT system. The figure clearly shows the crossover of nucleation from activated to barrierless diffusion at density indicated by a dashed bar. The supersaturation corresponding to the dashed line is the kinetic spinodal point. (Reproduced from Santra, M. and Bagchi, B., Phys. Rev. E, 83, 031602, 2011. With permission.)... 

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