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Schlagwörter:
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Zusammenfassung:
The role of orbitals beyond the Cu 3d O 2pσσ set employed in the widely used extended Hubbard model is considered with respect to low-energy charge excitations in cuprates. We focus on the description of the EELS and optical conductivity data of Sr2CuO3 and Sr2CuO2Cl2 with respect to O 2pπ2pπ states. Consequences for the orbital character of doped holes are discussed. The achieved novel description of the EELS data in transverse chain response is robust with respect to the addition of Cu 3dxy3dxy and 4s orbitals.