The electron-density distribution in KTiOPO4

A detailed account of X-ray diffraction measurements on single crystals of KTiOPO4 (potassium titanyl phosphate) is given. The experiments were carried out at room temperature and the data were used for the analysis of the electron-deformation density. We have been confronted with difficulties in obtaining a correct description of the electron density owing to the noncentrosymmetry of the crystal structure and the probable anharmonic thermal motion or local disorder of the potassium ions. The electron density indicates the presence of a strong covalent bond between Ti 4' and 0 2 ions. The possibility of relating the electron density to the high second-order electronic electric susceptibility of KTiOPO4 has previously been discussed by Hansen, Protas & Marnier [C. R. Acad. Sci. Ser. B (1988), 307, 475-478]. Crystal data: orthorhombic, Pna2j, a = 128209 (9), h -64052 (6), c = 105932 (9) A, V = 869.9 A 3, Z = 8, R(F) = 1.86% for 5053 reflections.