Structural features of the superconducting single crystals of YBa2Cu2.910O6.58

Tetragonal single crystals of YBa 2 Cu 2.910 O 6.58 with T c ∼45-60 K are grown in ZrO 2 crucibles. In the framework of the P4/mmm symmetry, a = 3.867(1), and c = 11,734(1) A, the atomic structure of the crystals is refined. An analysis of the structural data led us to conclude about the random nature of the tetragonal symmetry of these superconducting samples. The local symmetry of the crystals is orthorhombic. The tetragonality is simulated by the merohedral microtwins