title: Accurate X-Ray Spectral Predictions: An Advanced Self-Consistent-Field Approach Inspired by Many-Body Perturbation Theory.
abstract: Constrained-occupancy delta-self-consistent-field (ΔSCF) methods and many-body perturbation theories (MBPT) are two strategies for obtaining electronic excitations from first principles. Using the two distinct approaches, we study the O 1s core excitations that have become increasingly important for characterizing transition-metal oxides and understanding strong electronic correlation. The ΔSCF approach, in its current single-particle form, systematically underestimates the pre-edge intensity for chosen oxides, despite its success in weakly correlated systems. By contrast, the Bethe-Salpeter equation within MBPT predicts much better line shapes. This motivates one to reexamine the many-electron dynamics of x-ray excitations. We find that the single-particle ΔSCF approach can be rectified by explicitly calculating many-electron transition amplitudes, producing x-ray spectra in excellent agreement with experiments. This study paves the way to accurately predict x-ray near-edge spectral fingerprints for physics and materials science beyond the Bethe-Salpether equation.
authors.affiliation: The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
authors.forename: Yufeng
authors.initials: Y
authors.lastname: Liang
authors.affiliation: National Institute of Standards and Technology (NIST), Gaithersburg, Maryland 20899, USA.
authors.forename: John
authors.initials: J
authors.lastname: Vinson
authors.affiliation: The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
authors.forename: Sri
authors.initials: S
authors.lastname: Pemmaraju
authors.affiliation: Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
authors.forename: Walter S
authors.initials: WS
authors.lastname: Drisdell
authors.affiliation: National Institute of Standards and Technology (NIST), Gaithersburg, Maryland 20899, USA.
authors.forename: Eric L
authors.initials: EL
authors.lastname: Shirley
authors.affiliation: The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
authors.forename: David
authors.initials: D
authors.lastname: Prendergast