This award supports fundamental theoretical research and education on the conceptual foundations, extensions, and applications of density functional theory. Research will be performed in two areas: I. Density Functional Theory (DFT) The PI will use methods he recently developed to address unresolved basic questions involving spin magnetism. He further plans to extend earlier work into a new very broad regime, interactions of two non-overlapping systems of arbitrary composition, size, and shape. This work aims to improve density functional theory descriptions of Van der Waals interactions and is appropriate for many polymeric and biological systems. In previous work, the PI put forward the concept of "nearsightedness" as a fundamental property of many systems of very many atoms. The concept is that local properties near a point r depend significantly only on atoms and fields near r. The PI aims to quantitatively sharpen this concept which provides a fundamental basis for order N electronic structure methods and algorithms. II. Strong Time-Dependent Perturbations With an international collaborator, the PI plans to continue studies of the spectacular effects of very strong and very high frequency laser fields on molecules. Their previous work found that in the asymptotic regime of a very strong and very short laser pulse striking a molecule, the electronic charge cloud is lifted away rigidly from the nuclear "skeleton," which stays behind. Broader Impacts: (a) This work extends and enhances the intellectual foundation of density functional theory, the leading theoretical methodology for systems consisting of many atoms. (b) The broad area of highly non-linear effects in arbitrarily strong time-dependent laser fields is becoming accessible to experiment and is ripe for advance. (c) The PI lectures on his work to audiences ranging from elementary school children to senior professionals. (d) This award supports a valuable educational experience at the postdoctoral level. %%% This award supports fundamental research and education on the conceptual foundations of density functional theory, on its extensions, and applications. Density functional theory is the leading theoretical methodology for systems consisting of many atoms. As density functional theory-based methods have been applied to a growing number of diverse materials and problems from ice to spin polarized materials to time dependent systems, important conceptual questions have arisen. The PI's research aims to directly address these questions and place density functional theory based methods on a firm conceptual foundation. Broader Impacts: (a) This work extends and enhances the intellectual foundation of density functional theory, the leading theoretical methodology for systems consisting of many atoms. (b) The broad area of highly non-linear effects in arbitrarily strong time-dependent laser fields is becoming accessible to experiment and is ripe for advance. (c) The PI lectures on his work to audiences ranging from elementary school children to senior professionals. (d) This award supports a valuable educational experience at the postdoctoral level. ***
