Modification of twin boundaries in YBa2Cu3O6+δ, due to O ordering at below the temperature of the tetragonal-orthorhombic phase transformation, was studied by using mean field theory with spatial gradient terms for the O concentration variation. The distribution of O atoms across the twin boundaries was calculated at various temperatures and O concentrations. Based upon these calculations, the interfacial energy, the equilibrium thickness and the associated O ordering of the twin boundaries were deduced.

Structural Modification of Twin Boundaries in YBa2Cu3O6+δ Oxides - Effects of Oxygen Concentration and Temperature. Q.Meng, Y.Zhu: Physical Review B, 2007, 75[17], 174501 (7pp)