Site symmetry approach in the supercell model of carbon-doped ZnO bulk

Carbon-doped zinc oxide is one of promising materials for technological applications due to its ferromagnetism observed at room temperature. When using the hybrid DFT-HF Hamiltonian based on the PBE0 exchange-correlation functional for large-scale calculations on defective ZnO:C single crystal, we have shown that application of supercell model for carbon impurity located at O site of wurtzite-structured ZnO bulk results in the dependence of calculated formation energy of the point defect (E_form) on the selected site symmetry of the substituted atom in the supercell. For a more symmetric C_3v site usually used for simulation of defective ZnO structures, values of formation energy per single dopant in supercell essentially exceed those evaluated for less symmetric C₁ and C_s sites. On the other hand, each of these three types of E_form does not noticeably differ depending on supercell size if it is large enough to neglect lateral interaction between adjacent dopants. Influence of site symmetry on the electronic structure of C-doped ZnO is discussed too. The suggested approach can be further applied to a wide class of defects in crystalline solids allowing the detailed analysis of electron density localization in a defective crystal and more accurate reproducing the formation energy of point defect.