  Hard-sphere fluids confined between parallel plates a distance $D$ apart are
studied for a wide range of packing fractions, including also the onset of
crystallization, applying Monte Carlo simulation techniques and density
functional theory. The walls repel the hard spheres (of diameter $\sigma$) with
a Weeks-Chandler-Andersen (WCA) potential $V_{WCA}(z) = 4 \epsilon
[(\sigma_w/z)^{12}-(\sigma_w/z)^6 + 1/4]$, with range $\sigma_w = \sigma/2$. We
vary the strength $\epsilon$ over a wide range and the case of simple hard
walls is also treated for comparison. By the variation of $\epsilon$ one can
change both the surface excess packing fraction and the wall-fluid
$(\gamma_{wf})$ and wall-crystal $(\gamma_{wc})$ surface free energies. Several
different methods to extract $\gamma_{wf}$ and $\gamma_{wc}$ from Monte Carlo
(MC) simulations are implemented, and their accuracy and efficiency is
comparatively discussed. The density functional theory (DFT) using Fundamental
Measure functionals is found to be quantitatively accurate over a wide range of
packing fractions; small deviations between DFT and MC near the fluid to
crystal transition need to be studied further. Our results on density profiles
near soft walls could be useful to interpret corresponding experiments with
suitable colloidal dispersions.
