This project in the Theoretical and Computational Chemistry Program of the Chemistry Division involves an investigation of a number of aspects of the electronic structure of atoms and molecules with a focus on the structure of reduced density matrices, the extended Koopmans' theorem, and the development of analytic approximations to the electron-electron pair density. A goal is to obtain more accurate descriptions of ionization energies and the ionization process itself. Also being sought are improvements in the form of exchange-correlation potentials for use in density functional theories of electronic structure. %%% Descriptions of the electronic structure of atoms, molecules, and solids typically involve highly mathematical formulations which make their interpretations difficult. In this theoretical study ways are being sought to simplify the descriptions without loss of rigor. A particular focus of the study is the formulation of new mathematical descriptions of the important process of the removal of an electron from an atom or molecule to form a positive ion.
