Viscoelasticity and metastability limit in supercooled liquids

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 λ, which is essentially the ratio between the infinite frequency shear modulus and the enthalpy of fusion of the crystal. In systems where λis larger than a critical value λ_c the metastability limit is totally suppressed, independently of the surface tension. On the other hand, if λ< λ_c a kinetic spinodal is present and the time needed to experimentally observe it scales as exp[ω/(λ_c-λ)^2], where ωis roughly the ratio between surface tension and enthalpy of fusion.