The Explicit Density Functional, and its Connection with Entropy Maximisation.

Phil Attard

Ian Wark Research Institute, University of South Australia, The Levels, SA 5095, Australia

J. Stat. Phys. 100 , 445-473 (2000)

Abstract
The intrinsic Helmholtz free energy, commonly used as a basis for density functional theories, is here given explicitly as a cluster diagram expansion with density field points. Also given are explicit variational procedures for determining the chemical potential for a given density, the pair potential for a given pair correlation function, and the pair correlation function for a given pair potential. The physical meaning of the density functional is established within the context of a new derivation of statistical mechanics based on entropy that supplies a variational principle for equilibrium by generalising the thermodynamic potential to non-equlibrium states. This shows that the conventional density functional determines not only the equilibrium density, but also the probability of fluctuations about that density.

Key Words
Density Functional Theory, Cluster Diagrams, Maximum Entropy.

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