2015/01/20 by U. D. Wdowik, Urszula D. Wdowik, Przemysław Piekarz +7
Chemistry · Earth and Planetary Sciences · Materials Science · Physics and Astronomy · #Band gap #Chemistry #Condensed matter physics #Coulomb #Crystallography #Dielectric #Electron #High-pressure geophysics and materials #Ion #Materials science #Nuclear Materials and Properties #Phonon #Physics #Rare-earth and actinide compounds #Vacancy defect #cond-mat.str-el
paper · pdf · doi:10.1103/physrevb.91.195111
11 page, 8 figures
arxiv created 2015/01/20 · openalex publication_date 2015/05/08 · arxiv updated 2015/06/11 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
The influence of intrinsic Fe defects in FeO (either single cation vacancies or prototypical 4:1 vacancy clusters) on electronic and dielectric properties is studied within density-functional theory. The importance of local Coulomb interactions at Fe atoms is highlighted and shown to be responsible for the observed insulating Mott gap in FeO, which is reduced by the presence of defects. We investigate nonstoichiometric configurations of Fe_1\ensuremath-xO with x ranging from 3% to 9%, and we find the aliovalent Fe cations in both the regular and interstitial lattice sites of the considered configurations. Furthermore, we show that the trivalent Fe ions, induced by both isolated and clustered Fe vacancies, introduce the empty band states inside the insulating gap, which decreases monotonically with increasing cation vacancy concentration. The Fe_1\ensuremath-xO systems with high defect content become metallic for small values of the Coulomb interaction U, yielding an increase in the dielectric functions and optical reflectivity at low energies, in agreement with the experimental data. Due to the crystal defects, the infrared-active transverse optic phonons split and distribute over a wide range of frequencies, clarifying the origin of the exceptionally large spectral linewidths of the dielectric loss functions observed for w"ustite in recent experiments.