title: Communication: Hole localization in Al-doped quartz SiO2 within ab initio hybrid-functional DFT.
abstract: We investigate the long-standing problem of hole localization at the Al impurity in quartz SiO2, using a relatively recent DFT hybrid-functional method in which the exchange fraction is obtained 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.
authors.affiliation: Department of Energy, Politecnico di Milano, via Ponzio 34/3, 20133 Milano, Italy.
authors.forename: Matteo
authors.initials: M
authors.lastname: Gerosa
authors.affiliation: Dipartimento di Scienza dei Materiali, Università di Milano-Bicocca, via R. Cozzi 55, 20125 Milan, Italy.
authors.forename: Cristiana
authors.initials: C
authors.lastname: Di Valentin
authors.affiliation: Department of Energy, Politecnico di Milano, via Ponzio 34/3, 20133 Milano, Italy.
authors.forename: Carlo Enrico
authors.initials: CE
authors.lastname: Bottani
authors.affiliation: Dipartimento di Fisica dell' Universita' degli Studi di Milano and European Theoretical Spectroscopy Facility (ETSF), Via Celoria 16, 20133 Milan, Italy.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Onida
authors.affiliation: Dipartimento di Scienza dei Materiali, Università di Milano-Bicocca, via R. Cozzi 55, 20125 Milan, Italy.
authors.forename: Gianfranco
authors.initials: G
authors.lastname: Pacchioni