ON DETERMINING THE RELEVANCE OF ATHERMAL NUCLEATION IN RAPIDLY QUENCHED LIQUIDS

When a liquid is quenched, classical nucleation theory asserts that at least a fraction of the solid must nucleate by way of the athermal me chanism. In this letter, we show that this fundamental issue regarding the relative rates of athermal and thermal nucleation during a quench can be readily addressed by comparing the instantaneous quench rate t hat is in effect at any point during the quench, -dT/dt, to kn(+)/(pa rtial derivative n/partial derivative T) evaluated at the correspondi ng temperature. This and additional considerations permit the construc tion of a nucleation-mechanism diagram that maps out the thermal-mecha nism-dominated and athermal-mechanism-dominated domains in the quench- rate-temperature parameter space. By projecting the thermal trajectory of a quench on the diagram, the relevance or irrelevance of the ather mal mechanism, as well as the extent to which athermal mechanism parti cipates in the transformation, can be assessed. (C) 1998 American Inst itute of Physics.