Van der Waals Gaps in Sm1+xBa2−xCu3Oy and Their Effect on Superconductivity

We have used electron–positron annihilation to study superconducting cuprates Sm1+xBa2−xCu3Oy. We have determined the average radii for oxygen ions in Sm1+xBa2−xCu3Oy. 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 Sm1+xBa2−xCu3Oy on the superconducting transition temperature Tc and we have shown that Tc increases as ΔX inceases.