X-ray absorption in insulators with non-Hermitian real-time time-dependent density functional theory

Area of Science:

• Computational materials science
• Quantum chemistry
• Spectroscopy

Background:

• Accurate simulation of X-ray absorption spectra is crucial for understanding material properties.
• Traditional methods face challenges in precisely modeling core-level excitations.

Purpose of the Study:

• To compute the Si L-edge X-ray absorption spectrum of α-quartz.
• To validate a novel computational approach for core-level spectroscopy.

Main Methods:

• Employed non-Hermitian real-time time-dependent density functional theory (RT-TDDFT).
• Utilized an embedded finite cluster model with atom-centered basis sets.
• Applied tuned range-separated functionals and molecular orbital-based imaginary absorbing potentials.

Main Results:

• Obtained excited states in good agreement with experimental data for the Si L-edge spectrum.
• Successfully captured spectral features from the pre-edge to ~20 eV above the ionization edge.

Conclusions:

• The developed RT-TDDFT approach is effective for simulating core-level X-ray absorption spectra.
• This methodology is generalizable to diverse materials and core-level spectroscopy studies.