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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 19: Poster: Crystallization, Nucleation and Self Assembly
CPP 19.6: Poster
Dienstag, 12. März 2013, 18:15–20:15, Poster C
Free energies of fcc, hcp, and bcc phases of hard sphere crystals — •Mohammad Hossein Yamani and Martin Oettel — Institut für Angewandte Physik, Universität Tübingen, Germany
We use density functional theory of fundamental measure type (FMT) to evaluate
the fully unconstrained minimized periodic fcc, hcp and bcc crystal
profiles. Previous FMT results in the case of fcc compare very well to simulation results [1].
hcp and fcc differ only in the stacking sequence of hexagonally
packed planes of particles, and thus one expects only a small free-energy difference
between these two structures. FMT predicts hcp to be more
stable than fcc by a free energy difference per particle of the order of 0.001 kB T.
Instead, simulation results show that fcc is more stable than hcp by about the same free energy
difference. We rationalize these findings using Stillinger’s expansion [2] for the crystal
partition function in the number n of correlated, free particles in a matrix
of frozen particles at ideal lattice positions. It turns out that the stability of hcp over fcc
holds for a truncation at n=2, giving approximately the same hcp-fcc free energy difference
as FMT. For a reversal of stability truncation at higher n is required.
M. Oettel et al., Phys. Rev. E 82, 051404 (2010).
W. G. Rudd et al., J. Chem. Phys. 49, 4857 (1968).