  By combining interface-pinning simulations with numerical integration of the
Clausius-Clapeyron equation we determine accurately the melting-line
coexistence pressure and fluid/crystal densities of the Weeks-Chandler-Andersen
(WCA) system covering four decades of temperature. The data are used for
comparing the melting-line predictions of the Boltzmann,
Andersen-Weeks-Chandler, Barker-Henderson, and Stillinger hard-sphere
approximations. The Andersen-Weeks-Chandler and the Barker-Henderson theories
give the most accurate predictions, and they both work excellently in the
zero-temperature limit for which analytical expressions are derived here.
