Model for density-functional thermodynamic perturbation analysis of Lennard-Jones solids

Theoretical evidence for a dense fluid precursor to crystallization

We present classical density functional theory calculations of the free-energy landscape for fluids below their triple point as a function of density and crystallinity. We find that, both for a model globular protein and for a simple atomic fluid modeled with a Lennard-Jones interaction, it is free-energetically easier to crystallize by passing through a metastable dense fluid in accord with the Ostwald rule of stages but in contrast to the alternative of ordering and densifying at once as assumed in the classical picture of crystallization.

Self-consistent nonperturbative theory for classical systems

We construct a self-consistent nonperturbative theory for the structure and thermodynamics of a classical system of particles that goes beyond the usual approaches based on perturbation theory. Our theory, which gives accurate predictions for the phase diagram, is based on two ingredients: first, use is made of an exact expression for the free energy of a many-body system in terms of a reference system and a coupling integral connecting the latter to the final system; second, correlation functions may be very accurately approximated using a number of sum rules relating the radial distribution function with thermodynamic quantities. Consistency between the coupling integral expression and the sum rules may be achieved by means of a self-consistent process.

Particle excursions in colloidal crystals

We have performed synchrotron small-angle x-ray diffraction experiments on charge-stabilized colloidal crystals. The mean squared displacements, obtained from Debye-Waller factors, decrease with increasing density beyond freezing. Irrespective of the range of the repulsion, our data and previous results lie on a common curve, linearly scaled between the melting and close-packed densities. Surprisingly, the excursions are smaller than predicted by theory.