Combining time-dependent density functional theory and the $\Delta$SCF approach for accurate core-electron spectra

TL;DR

This paper presents a combined TDDFT and $ riangle$SCF method to accurately simulate core-electron spectra, aiding interpretation of X-ray absorption and EELS experiments.

Contribution

The study introduces a novel approach that integrates TDDFT with $ riangle$SCF for improved core-electron spectral calculations.

Findings

Encouraging agreement between calculated and experimental spectra.

Method effectively aligns TDDFT spectra with $ riangle$SCF energies.

Applicable to small molecules for spectral analysis.

Abstract

Spectroscopies that probe electronic excitations from core levels into unoccupied orbitals, such as X-ray absorption spectroscopy and electron energy loss spectroscopy, are widely used to gain insight into the electronic and chemical structure of materials. To support the interpretation of experimental spectra, we assess the performance of a first-principles approach that combines linear-response time-dependent density (TDDFT) functional theory with the $\Delta$~self\nobreakdash-consistent field ($\Delta$SCF) approach. In particular, we first use TDDFT to calculate the core-level spectrum and then shift the spectrum such that the lowest excitation energy from TDDFT agrees with that from $\Delta$SCF. We apply this method to several small molecules and find encouraging agreement between calculated and measured spectra.