MODELING OF A DEFECT REGION IN KDP CRYSTALS DOPED WITH TRIVALENT IRON

The crystal structure and some physical properties of KH2PO4 (KDP) cry stals have been modeled. Partly covalent pair potentials were determin ed using the MATAPOCS program. The set of parameters obtained was used to model (the GULP program) the defect region formed upon doping of a KDP crystal with Fe3+ ions. The potential of the Fe-O interaction was obtained by structural modeling of hematite. It is confirmed that the most appropriate position for incorporation of a Fe3+ ion is the posi tion (0.25 0.35 0.125); the position (0.75 0.22 0.125) is found to be less probable. It is shown that the distortion of the structure caused by the incorporation of Fe3+ ions reduces to rotation of PO4-tetrahed ra adjacent to the Fe3+ cation. The distortions arising in more remote tetrahedra are insignificant.