Efficient Simulation of Near-Edge X-ray Absorption Fine Structure (NEXAFS) in Density-Functional Theory: Comparison of Core-Level Constraining Approaches

Abstract

Widely employed Near-Edge X-Ray Absorption Fine Structure (NEXAFS) spectroscopy probes a system by excitation of core electrons to unoccupied states. A variety of different methodologies are available to simulate corresponding spectra from first-principles. Core-level occupation constraints within ground-state Density-Functional Theory (DFT) represent a numerically most efficient means to this end that provides access to large systems, examples being surface adsorption, proteins, polymers, liquids, and buried, condensed phase interfaces (e.q. solid-liquid and solid-solid). Here, we systematically investigate the performance of different realizations of this approximate approach through the simulation of K-edge NEXAFS-spectra of a set of carbon and nitrogen-containing organic molecules. Variational collapse to the ground state and oscillatory convergence are the major complications of these approximate computational protocols. We present a modified version of the maximum-overlap method to achieve a self-consistent inclusion of electrons in virtual states for systems where convergence is hampered due to degeneracies. Our results demonstrate that reliable spectra allowing for a semi-quantitative analysis of experimental data are already obtained at the semi-local level of density functionals and with standard numeric atomic orbital basis sets.

12 pages, 10 figures, The following article has been accepted by The Journal of Chemical Physics. After it is published, it will be found at https://dx.doi.org/10.1063/1.5083618

References in corpus (3)

• Delta Self-Consistent Field as a method to obtain potential energy surfaces of excited molecules on surfaces
• Interpretation of X-ray Absorption Spectroscopy in the Presence of Surface Hybridization
• Multireference X-Ray Emission and Absorption Spectroscopy calculations from Monte Carlo Configuration Interaction

Cited by in corpus (4)

• Highly Accurate Prediction of Core Spectra of Molecules at Density Functional Theory Cost: Attaining sub eV Error from a Restricted Open-Shell Kohn-Sham Approach
• Accurate prediction of core-level spectra of radicals at density functional theory cost via square gradient minimization and recoupling of mixed configurations
• Relativistic correction scheme for core-level binding energies from $GW$
• Interpreting Ultrafast Electron Transfer on Surfaces with a Converged First-Principles Newns-Anderson Chemisorption Function