Communication: Hole localization in Al-doped quartz SiO2 within ab initio hybrid-functional DFT

TL;DR

This study uses an advanced hybrid-functional DFT method to accurately model hole localization at Al impurities in quartz SiO2, improving upon previous approaches and providing insights into defect-related properties.

Contribution

It demonstrates the effectiveness of an ab initio derived hybrid-functional approach for modeling hole localization in quartz SiO2, surpassing traditional methods like B3LYP.

Findings

Accurate description of charge localization and structural distortion around Al centers.

Improved hyperfine parameter calculations compared to previous methods.

Limitations identified in computing defect excitation energies in low-dielectric materials.

Abstract

We investigate the long-standing problem of the hole localization at the Al impurity in quartz SiO$_2$, using a relatively recent DFT hybrid-functional method in which the exchange fraction is obtained \emph{ab initio}, based on an analogy with the static many-body COHSEX approximation to the electron self-energy. As the amount of the admixed exact exchange in hybrid functionals has been shown to be determinant for properly capturing the hole localization, this problem constitutes a prototypical benchmark for the accuracy of the method, allowing one to assess to what extent self-interaction effects are avoided. We obtain good results in terms of description of the charge localization and structural distortion around the Al center, improving with respect to the more popular B3LYP hybrid-functional approach. We also discuss the accuracy of computed hyperfine parameters, by comparison with previous calculations based on other self-interaction-free methods, as well as experimental values. We discuss and rationalize the limitations of our approach in computing defect-related excitation energies in low-dielectric-constant insulators.