9521353 Perdew This grant is being made to support theoretical research on the electronic structure of atoms, molecules and solids. The goal of the research is to improve methods and concepts of the density functional and pseudopotential theories through the following projects: (1) The exchange-correlation hole around an electron, describing the tendency of electrons to stay apart, is somewhat transferable from one system to another. For an electron gas of uniform density, the hole will be analyzed by spin and by interelectronic spatial separation. (2) An Oon-top holeO explanation will be given for the success of the local spin density and generalized gradient approximations in OnormalO systems. Exact or nearly exact holes in atoms and molecules will be used to test the strengths and weaknesses of these approximations. (3) Systematic local spin density and genralized gradient approximation calculations will be undertaken for the elemental solids. Local spin density and generalized gradient approximation energies will be analyzed by reduced density gradients. (4) To complete the liquid drop model for a charged metallic cluster, the quantum contribution to the size effect for the ionization energy will be evaluated. (5) A local electron-ion pseudopotential, combining simplicity with realism, has been constructed from solid state electron densities, Tests and applications will include calculation of phonon frequencies and OuniversalO phase diagrams for simple metals under pressure. (6) In a quest for Ochemical accuracy,O hybrid methods will be developed by combining density functionals for short-range correlations with wavefunction methods for long-range. (7) The density gradient expansion of the kinetic energy will be tested and convergently resummed, leading to a simple Oorder-NO method of electronic structure calculation. %%% Numerical and analytical techniques will be used to develop, test and apply new methods to calculate the properties of the electr onic structure of atoms, molecules and particularly, solids. The results of this work could have a wide-ranging impact on researchers using these methods to calculate a wide variety of material properties related to the electronic structure. ***
