Van der Waals Gaps in Sm1+x Ba2−x Cu3O y and Their Effect on Superconductivity

We have used electron–positron annihilation to study superconducting cuprates Sm_1+x Ba_2–x Cu₃O _y . We have determined the average radii for oxygen ions in Sm_1+x Ba_2–x Cu₃O _y . Taking into account the ion coordinates and their radii, we have constructed a geometric model for the arrangement of copper and oxygen ions in CuO₂ layers in the [b, c] plane, responsible for the superconductivity. From these data, we have determined the length of the ionic/covalent bonds and the width of the interionic gaps. We have established the effect of the features of the atomic structure of Sm_1+x Ba_2–x Cu₃O _y on the superconducting transition temperature T _c and we have shown that T _c increases as X inceases.