Viscoelasticity and metastability limit in supercooled liquids

TL;DR

This paper revisits classical nucleation theory for supercooled liquids, highlighting how viscoelastic effects and a key dimensionless parameter influence the existence of a metastability limit or kinetic spinodal.

Contribution

It introduces a new dimensionless parameter  that determines whether the metastability limit is suppressed or present, incorporating elastic effects into nucleation theory.

Findings

For  > _c, the metastability limit is suppressed.

The time to observe the spinodal scales exponentially with system parameters.

Elastic effects significantly alter the classical nucleation theory predictions.

Abstract

A supercooled liquid is said to have a kinetic spinodal if a temperature Tsp exists below which the liquid relaxation time exceeds the crystal nucleation time. We revisit classical nucleation theory taking into account the viscoelastic response of the liquid to the formation of crystal nuclei and find that the kinetic spinodal is strongly influenced by elastic effects. We introduce a dimensionless parameter \lambda, which is essentially the ratio between the infinite frequency shear modulus and the enthalpy of fusion of the crystal. In systems where \lambda is larger than a critical value \lambda_c the metastability limit is totally suppressed, independently of the surface tension. On the other hand, if \lambda < \lambda_c a kinetic spinodal is present and the time needed to experimentally observe it scales as exp[\omega/(\lambda_c-\lambda)^2], where \omega is roughly the ratio between surface tension and enthalpy of fusion.