  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 for both 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.
