Crystal structures of RbTiOAsO4, KTiO (P0. 58, As0. 42) O4, RbTiOPO4 and (Rb0. 465, K0. 535) TiOPO4, and analysis of pseudosymmetry in crystals of the KTiOPO4 family

The crystal structures of RbTiOAsO4, KTiO(P0.58,As0.42)O4, RbTiOPO4 and (Rb0.465,K0.535)TiOPO4, all of which are orthorhombic (space group Pna2(1)) and isostructural with KTiOPO4, have been determined from single-crystal X-ray diffraction data and refined to R factors between 0.027 and 0.040. The results are used for an analysis of structural trends in crystals of the KTiOPO4 family by comparison of the room-temperature structures with that proposed for the high-temperature prototypic phase (space group Pnan).