SrZn(VO)(PO4)2 und BaCd(VO)(PO4)2: Zum BaZn(VO)(PO4)2-Typ verwandte, jedoch nicht isotype Vanadylphosphate / SrZn(VO)(PO4)2 and BaCd(VO)(PO4)2: Vanadylphosphates Related but not Isotypic to the BaZn(VO)(PO4 )2 Type

Single crystals of the compounds SrZn(VO)(PO4)2 (I) and BaCd(VO)(PO4)2 (II) have been prepared by solid state reactions in evacuated quartz tubes. X-ray investigations confirmed orthorhombic symmetry, space group D152h-Pbca, lattice constants a/b/c (I): 9.066(1)/9.012(1)/17.513(1) Å and (II); 8.838(4)/8.915(4)/19.374(9) Å, Z = 8. Initially assumed isotypies of (I) and (II) to BaZn(VO)(PO4)2 proved to be erroneous considering significant details of the connectivity of the ZnO4 and PO4 tetrahedra (I) and the coordination sphere of cadmium (II), respectively. The similarities and differences of the crystal chemistry relation to (I) and (II) are discussed with respect to BaZn(VO)(PO4)2. The Coulomb terms of the lattice energies of vanadyl M2(VO)(PO4)2 and divanadyl M(VO)2(PO4)2 phosphates are shown.