Funct. Mater. 2026; 33 (2): 328-342.

The formation energies and equilibrium concentrations of native defects in yttrium aluminum garnet (Y₃Al₅O^{12, YAG) are investigated using density functional theory together with a thermodynamic analysis. The evolution of defect charge states during cooling from the crystal-growth temperature to room temperature is analyzed. The calculations show that cooling activates charge transfer between defect centers and leads to a significant redistribution of defects among their possible charge states. As a consequence, only a limited number of charge states remain thermodynamically favorable for each defect type at low temperatures. The proposed theoretical approach can be applied to other oxide crystals in which defect concentrations are established at high synthesis temperatures, while the functional properties of the material are determined at much lower operating temperatures.}