Atomistic modeling of native point defects in yttrium aluminum garnet crystals

Native point defects in yttrium aluminum garnet (YAG) are studied in the fr amework of the pair-potential approximation, coupled with the shell-model d escription of the lattice ions. For the perfect lattice, a new set of poten tial parameters is obtained; these parameters reproduce the structure, elas tic, and dielectric constants of YAG very well. The calculated formulation energies for native defects suggest that antisite disorder is preferred ove r Frenkel and Schottky-like disorder in YAG. The calculated values of the d istortion that is caused by the antisite Y atom that substitutes in the Al site in the lattice are in excellent agreement with the extended,X-ray abso rption fine-structure (EXAFS) measurements. In nonstoichiometric YAG, the c alculated reaction energies indicate that excess Y2O3 or Al2O3 most likely is accommodated by the formation of antisites, rather than vacancies, in th e lattice.