SINGLE-CRYSTAL STRUCTURE DETERMINATION OF DOUBLE-LAYERED STRONTIUM IRIDIUM OXIDE [SR3IR2O7]

Single crystals of Sr3Ir2O7 were grown for the first time from a SrCl2 flux using SrO2 and IrO2 in a sealed Pt tube under ambient pressure. The compound crystallizes in a tetragonal unit cell [a = 3.896 (1) and c = 20.879 (3) angstrom] with space group I4/mmm (No. 139) and Z = 2. The crystal structure was solved by means of single crystal X-ray diffraction and refined to R = 0.014. The structural refinement showed that the IrO6 octahedra are rotated about the c-axis by about 12 degrees, similar to the rotational distortion recently found in Sr2IrO4. However, unlike in Sr2IrO4, the IrO6 rotations in Sr3Ir2O7 are not correlated, hence no superlattice reflections appear.