Failure of the charge-transfer hypothesis for superconductivity in YBa2Cu3Ox and in La2-beta S beta CuO4

By extracting the layer-charges in YBa2Cu3Ox as functions of dopant oxygen content x from neutron diffraction data (using the bond-valence-sum method), we show that the charge-transfer hypothesis of high-temperature cuprate-plane superconductivity fails to describe the data. A similar failure occurs for La2-betaSrbetaCuO4 as a function of Sr dopant concentration, and was implicitly predicted (before the charge-transfer hypothesis was enunciated) by self-consistent local-density-approximation calculations of R. V. Kasowski, M.-H. Tsai, J. D. Dow, and M. T. Czyzyk [Physica C 162, 1349 (1989)]. Both failures can be traced to difficulties the hypothesis has with (i) the rules of chemistry which require electronegative dopants such as oxygen to attract electrons, not holes, and (ii) the law of conservation of (neutral) charge in each unit cell. (C) 1997 American Institute of Physics.