ELECTRONIC-PROPERTIES OF CA2CUO2CL2 AND CA2CUO2BR2

The linear augmented-plane-wave method has been applied to calculate the electronic band properties of the halo-oxocuprates Ca2CuO2Cl2 and Ca2CuO2Br2, a class of quaternaries that form with the same K2NiF4-type structure as La2CuO4. The results exhibit the same generic features that characterize previous cuprate superconductor parent compounds such as La2CuO4, including a single half-filled Cu d(x2-y2) O p(x,y) -antibonding subband at EF. A tight-binding analysis shows that the qualitative differences between the valence-band results at lower energies for the halo-oxocuprates and La2CuO4 are due to the increased binding energies [relative to Cu(3d)] of the Br(4p) (0.5 eV) and Cl(3p) (1.3 eV) states as compared with the apical O(2p) (0.1 eV) states. © 1990 The American Physical Society.