Hillert Materials Modeling Colloquium series III: More-predictive density functionals, symmetry breaking, and strong correlation

Approximate density functionals constructed to satisfy known mathematical properties of the exact density functional for the exchange-correlation energy of a many-electron system can be predictive over a wide range of materials and molecules. The strongly constrained and appropriately normed (SCAN) meta generalized gradient approximation satisfies 17 exact constraints, and nicely describes some systems that were formerly thought to be beyond the reach of density functional theory, such as the cuprates. In some cases (e.g., barrier heights to chemical reactions and hydrogen bonds in water), SCAN is dramatically more accurate when evaluated on the Hartree-Fock density than it is on its own self-consistent and more delocalizing density.

Ground states that break the symmetry of a Coulomb-interacting Hamiltonian can be understood as dynamic density or spin density fluctuations that drop to low or zero frequency and so persist over long times. In many cases, symmetry breaking transforms the strong correlation in a symmetry-unbroken wave function into moderate correlation like that found in the uniform electron gas of high or valence-electron density (an “appropriate norm” for constraint-based approximations).

Lecturer

John P. Perdew is a developer of first-principles density functional theory for atoms, molecules, and solids. The wide use of this theory in physics, chemistry, and materials science has made him one of the most-cited physicists in the world. He derived properties of the exact density functional for the exchange-correlation energy, including its spin scaling and uniform-density scaling, and the linear variation of the total energy between adjacent integer electron numbers. He developed popular approximations including PBE (1996) and SCAN (2015).

Perdew received a Ph.D. in Physics from Cornell University in 1971, followed by postdoctoral research at U. of Toronto and Rutgers U. In 1977, he became a faculty member at Tulane U. in New Orleans. His research has been supported by the NSF since 1978. He was elected to the National Academy of Sciences in 2011. In 2013, he joined Temple U. From 2014 to 2020, he was the Director of two DOE-supported Energy Frontier Research Centers at Temple.

Hillert Materials Modeling Colloquium Series is arranged by Hillert Modeling Laboratory
Department of Materials Science and Engineering
KTH Royal Institute of Technology

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