ABILITY OF NONPERTURBATIVE DENSITY-FUNCTIONAL THEORIES TO STABILIZE ARBITRARY SOLIDS

The effects of solid structure and interatomic potential are investigated for density-functional theories based on the definition of a weighted or effective density for approximating the solid phase in terms of the uniform liquid. The introduction of solidlike structure to the modified-weighted-density-approximation (MWDA) theory of Denton and Ashcroft [Phys. Rev. A 39, 4701 (1989)] leads to loss of existence of the weighted density for a system of hard spheres. This behavior is more pronounced for loose crystalline structures, such as the diamond lattice. By contrast, the generalized-effective-liquid-approximation theory (GELA) of Lutsko and Baus [Phys. Rev. A 41, 6647 (1990)] always predicts single-valued weighted densities in the cases studied here. The thermodynamic mapping, which is the core of both of the MWDA and GELA approximations, is ineffective for Lennard-Jones fluids, according to a criterion for the relative stability of the solid phase evaluated using liquid-state information.