Adrienn Ruzsinszky, John P. Perdew, and Jianwei Sun of Tulane University are supported by an award from the Chemical Theory, Models and Computational Methods program in the Division of Chemistry to develop density functionals on higher levels of a hierarchy of approximations. Density functional theory is very widely used in chemistry, physics, materials science and engineering, and even geology and pharmaceutical design. It enables practical computer calculations predicting the existence and properties of systems of many interacting electrons. The five rungs of the ladder of approximations to the exact density functional for the exchange-correlation energy of a many-electron system provide a range of options for electronic structure calculations for molecules and materials, from the more affordable first three rungs (local spin density approximation or LSDA, generalized gradient approximation or GGA, and meta-GGA) to the more expensive but often more accurate fourth and fifth rungs (hybrids and self-interaction corrections and random phase approximation RPA-like functionals). While the first two rungs of the ladder of approximations have been broadly explored, the third, fourth, and fifth rungs harbor numerous opportunities for improvement. The proposed plan is a comprehensive effort to make higher levels of the ladder of density functional approximations more accurate but still computationally feasible. The broader impacts of the proposed project will include more-accurate r