title: First-Principles Study of Antisite Defect Configurations in ZnGa2O4:Cr Persistent Phosphors.
abstract: Zinc gallate doped with chromium is a recently developed near-infrared emitting persistent phosphor, which is now extensively studied for in vivo bioimaging and security applications. The precise mechanism of this persistent luminescence relies on defects, in particular, on antisite defects and antisite pairs. A theoretical model combining the solid host, the dopant, and/or antisite defects is constructed to elucidate the mutual interactions in these complex materials. Energies of formation as well as dopant, and defect energies are calculated through density-functional theory simulations of large periodic supercells. The calculations support the chromium substitution on the slightly distorted octahedrally coordinated gallium site, and additional energy levels are introduced in the band gap of the host. Antisite pairs are found to be energetically favored over isolated antisites due to significant charge compensation as shown by calculated Hirshfeld-I charges. Significant structural distortions are found around all antisite defects. The local Cr surrounding is mainly distorted due to a ZnGa antisite. The stability analysis reveals that the distance between both antisites dominates the overall stability picture of the material containing the Cr dopant and an antisite pair. The findings are further rationalized using calculated densities of states and Hirshfeld-I charges.
authors: Center for Molecular Modeling (CMM), Ghent University , Technologiepark 903, 9052 Zwijnaarde, Belgium.
authors: Arthur
authors: A
authors: De Vos
authors: Center for Molecular Modeling (CMM), Ghent University , Technologiepark 903, 9052 Zwijnaarde, Belgium.
authors: Kurt
authors: K
authors: Lejaeghere
authors: Center for Molecular Modeling (CMM), Ghent University , Technologiepark 903, 9052 Zwijnaarde, Belgium.|Center for Ordered Materials, Organometallics and Catalysis (COMOC), Department of Inorganic and Physical Chemistry, Ghent University , Krijgslaan 281 (S3), 9000 Ghent, Belgium.
authors: Danny E P
authors: DE
authors: Vanpoucke
authors: LumiLab, Department of Solid State Sciences, Ghent University , Krijgslaan 281 (S1), 9000 Ghent, Belgium.|Center for Nano- and Biophotonics, Ghent University , Sint-Pietersnieuwstraat 41, 9000 Ghent, Belgium.
authors: Jonas J
authors: JJ
authors: Joos
authors: LumiLab, Department of Solid State Sciences, Ghent University , Krijgslaan 281 (S1), 9000 Ghent, Belgium.|Center for Nano- and Biophotonics, Ghent University , Sint-Pietersnieuwstraat 41, 9000 Ghent, Belgium.
authors: Philippe F
authors: PF
authors: Smet
authors: Center for Molecular Modeling (CMM), Ghent University , Technologiepark 903, 9052 Zwijnaarde, Belgium.
authors: Karen
authors: K
authors: Hemelsoet