Local kinetic energy and local temperature in the density-functional theory of electronic structure

Various thermodynamic elements of the density functional theory of electronic structure are reviewed and clarified. Detailed argumentation is given for the particular "del dot del" definition of the local kinetic energy density and local temperature. The temperature measures the "nighness" of an electron pair, thus playing a key role in quantitative (exchange and kinetic energy functionals) and qualitative (electron localization functions) tools based on the electron pair density. Two different derivations are given of the Gaussian model for the phase-space distribution function, from which one obtains an approximation to the entropy of the charge distribution. The full thermodynamic description is briefly discussed. (C) 2002 Wiley Periodicals, Inc.