Thursday, April 03, 2014
Quantum Embedding with Symmetry Breaking and Restoration:
A Quantum Chemistry Approach to Molecular and Materials Modelling
4:00 PM - 5:30 PM
Speaker: Gustavo Scuseria, Rice University
Abstract: Despite its enormous success for both molecules and solids, modern density functional theory
(DFT) faces significant hurdles for improving its current accuracy. The way forward in DFT has
been to add pieces of wavefunction theory to it. This all started when Hartree-Fock exchange
was included in the successful hybrid functionals. In solid state, the HSE screened hybrid
has brought predictions of band structure and density of states (even of difficult materials
like metal oxides) to unprecedented levels of accuracy. Yet, when strong correlations and
emerging collective phenomena are present (e.g., superconductivity), this all breaks down.
During the last few years, our research group has embarked in a quest for designing a wave
function based electronic structure methodology that would be applicable to both molecules
and solids, especially in the presence of strong correlations. The aim is to achieve this goal with
low (polynomial, not combinatorial) computational cost. This talk will discuss (mostly at the
conceptual level) the different pieces that go into such model and present benchmark results
along the way. The two major pieces of the model are: (1) symmetry breaking and restoration
as an impurity solver; (2) density matrix quantum embedding to capture entanglement of a
strongly correlated unit cell with a bath mimicking the rest of the system. While this task is
far from being completed, I will report on several successful milestones that make us very
optimistic about the future of this model.
 Projected quasiparticle theory for molecular electronic structure, G. E. Scuseria, C. A. Jimenez-Hoyos, T. M.
Henderson, J. K. Ellis, and K. Samanta, J. Chem. Phys. 135, 124108 (2011).
 Projected Hartree-Fock theory, C. A. Jimenez-Hoyos, T. M. Henderson, and G. E. Scuseria, J. Chem. Phys. 136,
 Multi-reference symmetry-projected variational approaches for ground and excited states of the one-dimensional
Hubbard model, R. R. Rodríguez-Guzmán, C. A. Jiménez-Hoyos, R. Schutski, and G. E. Scuseria, Phys. Rev. B 87,
 Density matrix embedding theory from broken symmetry mean fields, I. W. Bulik, G. E. Scuseria, and J.
Dukelsky, Phys. Rev. B 89, 035140 (2014).