Activation energy for solid nucleation in overpressurized superfluid He-4

Activation energy for solid nucleation in overpressurized superfluid He-4 is calculated. On the basis of a model free energy of solidification of superfluid He-4, I found that both the critical shape of nucleus and the activation energy deviate from the standard model (the 'hin wall' model) as pressure increases. These deviations are similar, even quantitatively, to what Harrowell and Oxtoby (J. Chem. Phys. 80:1639, 1984) calculated for solid nucleation in a supercooled classical liquid. The activation energy can be a few times greater than what the thin wall model predicts.