A comparative study of the electronic structures of SrCu2O2 and PbCu2O2 by density functional theory, high resolution X-ray photoemission and electron paramagnetic resonance spectroscopy

K. G. Godinho; G. W. Watson; A. Walsh; A. J. H. Green; D. J. Payne; J. Harmer; R. G. Egdell

doi:10.1039/B719364E

A comparative study of the electronic structures of SrCu₂O₂ and PbCu₂O₂ by density functional theory, high resolution X-ray photoemission and electron paramagnetic resonance spectroscopy†

K. G. Godinho,^a G. W. Watson,^a A. Walsh,^ab A. J. H. Green,^c D. J. Payne,^c J. Harmer^c and R. G. Egdell*^c

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* Corresponding authors

^a School of Chemistry, University of Dublin, Trinity College, Dublin, Ireland

^b National Renewable Energy Laboratory, Golden, CO, USA

^c Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, South Parks Road, Oxford, UK
E-mail: russell.egdell@chem.ox.ac.uk

Abstract

The electronic structures of SrCu₂O₂ and PbCu₂O₂ have been studied by density functional theory calculations in conjunction with high resolution X-ray photoemission spectroscopy (XPS) and electron paramagnetic resonance spectroscopy (EPR). In both materials there is linear O–Cu–O coordination and a band of Cu 3d states sits above a band of O 2p states, but with strong hybridisation between the two. The Pb ions in PbCu₂O₂ introduce new states of dominant Pb 6s atomic character below the bottom of the O 2p valence band together with states of mixed Pb 6s, O 2p and Cu 3d character at the top of the O 2p valence band. Hole states introduced by K doping in PbCu₂O₂ are shown to reside in anisotropic sites with clearly defined hyperfine couplings to ⁶³Cu as revealed by EPR. Broadening of the EPR signal in K-doped SrCu₂O₂ is associated with averaging of the g value and Cu hyperfine anisotropy due to facile hole hopping. It is concluded that replacement of Sr with Pb does not facilitate delocalisation of the holes.

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DOI: https://doi.org/10.1039/B719364E
Article type: Paper
Submitted: 14 Dec 2007
Accepted: 04 Apr 2008
First published: 24 Apr 2008

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J. Mater. Chem., 2008,18, 2798-2806

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A comparative study of the electronic structures of SrCu₂O₂ and PbCu₂O₂ by density functional theory, high resolution X-ray photoemission and electron paramagnetic resonance spectroscopy

K. G. Godinho, G. W. Watson, A. Walsh, A. J. H. Green, D. J. Payne, J. Harmer and R. G. Egdell, J. Mater. Chem., 2008, 18, 2798 DOI: 10.1039/B719364E

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Journal of Materials Chemistry