Candidate Presentation-March 26, 2012

Random Walks in Search of the “Divine" Functional

Abstract: One of the most important theoretical formulations of quantum physics is density functional theory (DFT) -- the foundational approach for modern theories for the electronic structure of materials. DFT is based on a fundamental, universal mapping, or functional, between the electron density of any electronic system and that system's electronic ground-state energy. The proof of existence of this functional has long been known, and many relatively successful approximations to it have been developed over the years, but the nature of the exact mapping actually used by nature, nicknamed the "divine" functional, has eluded investigators' grasp. I report progress in the search for this "divine" functional based on Monte Carlo simulations of the exchange-correlation (XC) hole for atoms, molecules and solids. This measures the change in electron density surrounding the position of an electron due to Pauli exclusion and Coulomb repulsion, a key theoretical input into DFT. Our data indicate the importance of the Laplacian of the density as a variable in modeling the XC hole and thus improving to our understanding of the universal "divine" density functional. We also find an unexpected error in how self-interaction error is typically corrected for small size systems, a problem relevant for molecular electronics.

by
Antonio Cancio
Assistant Professor, Ball State University

Monday, March 26, 2012
4:00 PM
CP 144