Density functional theory of soft sphere freezing

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Abstract
The freezing transition of ‘‘soft spheres,’’ which interact via inverse‐power potentials v(r)∼r−n, is systematically investigated for various values of the steepness n, using density functional theory. Two ‘‘second‐order’’ theories are considered, which require as only input the static pair structure of the homogeneous fluid. Both theories overestimate the densities of the coexisting fluid and solid phases, and the disagreement with computer simulation data worsens as the steepness n decreases. The two theories also predict that the fcc phase is more stable than the bcc phase for all n, which contradicts the behavior expected for soft repulsions.