Density Functional Descriptions of Classical Inhomogeneous Fluids

Abstract

Microscopically inhomogeneous states such as crystals and amorphous phases are wide-spread in nature, and it has become relatively common to attempt to describe the thermodynamic functions of such structured systems by utilising the corresponding properties of their homogeneous counterparts. One route is via density functional theory, some aspects of which are reviewed and developed here for single-component systems. In particular the possible applicability of coarse-graining or weighted density approximations to the theory of the liquid–crystal transition are discussed in terms of physical implications stemming from the crucial change in symmetry that occurs. Some insight into the apparent inconsistency of weighted-density approaches can be gained by examination of the role of anharmonic terms in the structured phase, and their relation to the nature of the interactions which also control the range of the weight-functions.