Multi-code Benchmark on Ti K-edge X-ray Absorption Spectra of Ti-O Compounds*

X-ray absorption spectroscopy (XAS) is an element-specific materials characterization technique that is sensitive to structural and electronic properties. First-principles simulated XAS has been widely used as a powerful tool to interpret the experimental spectra and draw physical insights. Recently, there has also been growing interest in building computational XAS databases to enable data analytics and machine learning applications. However, there are non-trivial differences among several commonly used XAS simulation codes, both in underlying formalism and technical implementation. Developing reliable and reproducible computational XAS databases calls for systematic benchmark studies.

 

In this work, we benchmarked Ti K-edge XAS simulations of ten representative Ti-O binary compounds, which we refer to as the Ti-O-10 dataset, using three state-of-the-art codes: XSPECTRA, OCEAN and exciting. We systematically studied the convergence behavior with respect to the input parameters and developed a workflow to automate and standardize the calculations to ensure converged spectra. Our benchmark comparison shows: (1) the two Bethe-Salpeter equation (BSE) codes (OCEAN and exciting) have excellent agreement in the energy range studied (up to 35 eV above the onset) with an average Spearman’s correlation score of 0.998; (2) good agreement is obtained between the core-hole potential (CHP) code (XSPECTRA) and BSE codes (OCEAN and exciting) with an average Spearman’s correlation score of 0.990. Our benchmark study provides important standards for first-principles XAS simulations with broad impact in data-driven XAS analysis.