  We study the phase behaviour of a binary mixture of colloidal hard spheres
and freely-jointed chains of beads using Monte Carlo simulations. Recently
Panagiotopoulos and coworkers predicted [Nat. Commun. 5, 4472 (2014)] that the
hexagonal close packed (HCP) structure of hard spheres can be stabilized in
such a mixture due to the interplay between polymer and the void structure in
the crystal phase. Their predictions were based on estimates of the free-energy
penalty for adding a single hard polymer chain in the HCP and the competing
face centered cubic (FCC) phase. Here we calculate the phase diagram using
free-energy calculations of the full binary mixture and find a broad
fluid-solid coexistence region and a metastable gas-liquid coexistence region.
For the colloid-monomer size ratio considered in this work, we find that the
HCP phase is only stable in a small window at relatively high polymer reservoir
packing fractions, where the coexisting HCP phase is nearly close packed.
Additionally we investigate the structure and dynamic behaviour of these
mixtures.
