# Classification of Local Chemical Environments from X-ray Absorption Spectra using Supervised Machine Learning

## TL;DR

This paper introduces a machine learning approach to classify local chemical environments from X-ray absorption spectra, achieving high accuracy and revealing spectral features important for structural determination.

## Contribution

The study develops a supervised machine learning method for classifying local environments from XANES spectra, surpassing empirical fingerprint techniques in accuracy and transferability.

## Key findings

- Achieved 86% average accuracy across oxides of 3d transition metals.
- Spectral features beyond the preedge are crucial for accurate classification.
- Machine learning classifiers can learn spectral features without human bias.

## Abstract

X-ray absorption spectroscopy is a premier element-specific technique for materials characterization. Specifically, the x-ray absorption near-edge structure (XANES) encodes important information about the local chemical environment of an absorbing atom, including coordination number, symmetry, and oxidation state. Interpreting XANES spectra is a key step towards understanding the structural and electronic properties of materials, and as such, extracting structural and electronic descriptors from XANES spectra is akin to solving a challenging inverse problem. Existing methods rely on empirical fingerprints, which are often qualitative or semiquantitative and not transferable. In this paper, we present a machine learning-based approach, which is capable of classifying the local coordination environments of the absorbing atom from simulated K-edge XANES spectra. The machine learning classifiers can learn important spectral features in a broad energy range without human bias and once trained, can make predictions on the fly. The robustness and fidelity of the machine learning method are demonstrated by an average 86% accuracy across the wide chemical space of oxides in eight 3d transition-metal families. We found that spectral features beyond the preedge region play an important role in the local structure classification problem especially for the late 3d transition-metal elements.