SRZN(VO)(PO4)(2) AND BACD(VO)(PO4)(2) - V ANADYLPHOSPHATES 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 qua rtz tubes. X-ray investigations confirmed orthorhombic symmetry, space group D-2h(15)-Pbca, lattice constants a/b/c (I): 9.066(1)/9.012(1)/1 7.513(1) Angstrom and (II): 8.838(4)/8.915(4)/19.374(9) Angstrom, Z = 8. Initially assumed isotypies of (I) and (II) to BaZn(VO)(PO4)(2) pro ved to be erroneous considering significant details of the connectivit y of the ZnO4 and PO4 tetrahedra (I) and the coordination sphere of ca dmium (II), respectively. The similarities and differences of the crys tal chemistry relation to (I) and (II) are discussed with respect to B aZn(VO)(PO4)(2). The Coulomb terms of the lattice energies of vanadyl M-2(VO)(PO4)(2) and divanadyl M(VO)(2)(PO4)(2) phosphates are shown.