PRESSURE EFFECT IN THE HG-BASED SUPERCONDUCTORS - A STRUCTURAL STUDY

Energy-dispersive synchrotron x-ray-diffraction studies were performed on powder samples of Hg1212 and Hg1223 in a diamond-anvil cell at pre ssure up to 300 kbar. High compressibility was found. A reversible str uctural transition was observed, which is suggested to correspond to a pressure-induced ordering along the c axis. The accommodation of the Ba ion at high pressure is studied, and the effect it might have on th e electronic structure of these materials is discussed by employing re sults from cluster calculations.