We examine the region of validity of Langer's picture of homogeneous nucleation. Our approach is based on a coarse-grained free energy that incorporates the effect of fluctuations with momenta above a scale k, The nucleation rate I = A(k)exp(-S-k) is exponentially suppressed by the action S-k of the saddle-point configuration that dominates tunnelling. The factor A(k) includes a fluctuation determinant around this saddle point. Both S-k and A(k) depend on the choice of k, but, for 1/k close to the characteristic length scale of the saddle point, this dependence cancels in the expression for the nucleation rate. For very weak first-order phase transitions or in the vicinity of the spinodal decomposition line, the pre-exponential factor A(k) compensates the exponential suppression exp(-S-k). In these regions the standard nucleation picture breaks down. We give an approximate expression for A(k) in terms of the saddle-point profile, which can be used for quantitative estimates and practical tests of the validity of homogeneous nucleation theory, (C) 1999 Elsevier Science B.V. All rights reserved.
|Autori interni:||STRUMIA, ALESSANDRO|
|Autori:||Strumia A; Tetradis N; Wetterich C|
|Titolo:||The region of validity of homogeneous nucleation theory|
|Anno del prodotto:||1999|
|Digital Object Identifier (DOI):||10.1016/S0370-2693(99)01158-2|
|Appare nelle tipologie:||1.1 Articolo in rivista|