PRESSURE-DEPENDENT ELECTRONIC-STRUCTURE AND DOPING IN HGBA2CA2CU3O8+DELTA

Local-density approximation electronic structure calculations are reported for HgBa2Ca2Cu3O8+delta both at ambient pressure and at 9.2 GPa. The apical O height was relaxed using total energy minimization. These calculations, which were performed for delta = 0.5 within a supercell geometry, show that the doping level of the CuO2 planes does increase under pressure. However, the increase is found to be quite modest amounting to less than 0.02 additional holes per Cu atom at 9.2 GPa. We suggest that variations in the doping level under pressure may not be solely responsible for the large increases observed in the superconducting critical temperature of this material.