Modeling of a Cubic Antiferromagnetic Cuprate Super-Cage

Abstract

Convex polyhedral cuprate clusters are being formed through lateral frustration when the a and c lattice parameters of the tetragonal ACuO 2 infinite layer structure will become identical by substitution of a large cation (A = Ba 2+ ). However, the corner-shared CuO 2 plaquettes of the infinite network suffer a topotactic rearrangement forming edge-connected units, for instance Cu 18 O 24 cages (polyhedron notation [4 6 4 12 3 8 ]) with <90° ferromagnetic super-exchange interaction as found in cubic BaCuO2. Cage formation via a hypothetical tetragonal BaCuO 2 compound (space group P4/ nmm) will be discussed. The possibility to construct a cuprate super-cage with m3m symmetry (polyhedron notation [4 6 4 12 4 24 3 8 ]) is being reported. This super-cage still consists of edge-connected CuO 2 plaquettes when fully decorated with copper ions, but with different curvatures, arranged in circles of 9.39 ? of diameter with 139.2° Cu-O-Cu antiferromagnetic super-exchange interaction. On the one hand, the realization of such a quite stable cuprate super-cage as a candidate for high-T c superconductivity depends on whether a template of suitable size such as the cation or C(CH 3 ) 4 enables its formation, and on the other hand the cage can further be stabilized by highly charged cations located along the [111] direction. Synthesis options will be proposed based on suggested cage formation pathways. An X-ray powder pattern was calculated for a less dense cluster structure of Im3m space group with a lattice parameter of a = 14.938 ? and two formula units of Cu 46 O 51 to facilitate future identification. Characteristic X-ray scattering features as identification tool were obtained when the electron distribution of the hollow polyhedron was approximated with electron density in a spherical shell.