SIMPLE-MODEL FOR ESTIMATING THE ANISOTROPIC COMPRESSIBILITY OF HIGH-TEMPERATURE SUPERCONDUCTORS

Using the concepts of "Comparative crystal chemistry", utilized by Hazen and Finger for insulating oxides, we have developed a model to estimate the anisotropic compressibility of high temperature superconductors. This model yields volume compressibilities within 10% of the accurate experimental values found by neutron diffraction on the superconducting oxides and accounts approximately for their compressibility anisotropy. In this model, the cation-anion coordination polyhedra, which themselves have different volumes and compressibilities, are considered. The compressibility of the bulk sample is then estimated by evaluating the compressibility of the individual layers in the layered structure. Estimates are made for the anisotropic compressibility of a large number of high temperature superconductors, including the many, like the electron-doped systems, whose compressibility has not yet been determined experimentally.