# Improving Density Functionals for Atoms, Molecules, and Solids

**When:**Friday, February 24, 2012 at 4:00 pm

**Where:**DA 114

**Speaker**: Adrienn Ruzsinszky

**Organization**: Department of Physics and Engineering Physics, Tulane University, New Orleans

**Sponsor**: Physics Colloquium

Kohn-Sham density functional theory is an exact-in-principle way to compute the ground-state energy and electron density of a many-electron system by solving a computationally-efficient self-consistent one-electron Schrödinger equation. In practice, the many-body effects of exchange and correlation must be approximated. This talk will begin by explaining what this theory can do. The standard semilocal approximations (local density and generalized gradient approximations) and their limitations will be reviewed. Improved semilocal approximations that work better for solids, or for solids and molecules, will be presented along with the results of numerical tests. In particular, promising results are obtained for molecules adsorbed on metal surfaces, a problem for which generalized gradient approximations can only get some properties right by getting others wrong. Finally, as a direction for further improvement, fully nonlocal approximations (hybrids with exact exchange, random phase approximation, and corrections to RPA) will be discussed. Possible future applications include structural phase transitions in solids, strongly-correlated systems, etc.