Detailed crystal structures of high-Tc superconductors Pb2Sr2Y0.90Sr0.10Cu 3O8, Pb2Sr2Y1-xCaxCu3O 8 (x=0.25 and 0.41) and Pb2Sr2Ho0.64Ca0.36Cu 3O8 were successfully determined by means of single crystal X-ray diffraction at room temperature. Space symmetry changes from C2/m (x=0.10 and 0.25) to Cmmm (x=0.36 and 0.41) with increasing divalent cation concentration, x. Their electron density distributions are determined by means of the maximum entropy method (MEM). Two- or four-splitting oxygen peaks clearly appear in the electron density maps of PbO plane, which is consistent with oxygen disorder models introduced to the present structure determination. In the electron density maps of monovalent copper plane, no peak corresponding to excess oxygens was observed at the 1 × 103 e/nm3 contour level. In the vicinities of divalent copper in the conducting plane, some anomalous electron density distribution is represented in the yttrium compounds.
- Electron density distribution
- High-t superconductor
- Maximum entropy method (mem)
- X-ray diffraction
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