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First-principles calculations have been used to investigate the electronic structure and energetics of the simple tetragonal SrCuO2 (P4/mmm) and its high-pressure tetragonal superstructure (P4/mmm). Based on the calculations, the high-pressure phase is metastable as compared with the low pressure tetragonal phase, with an energy difference of 0.13eV per SrCuO 2 formula unit. The energy barrier to the transition from the superstructure to the simple tetragonal structure is 0.24eV at 7GPa; thus, high temperatures are required to synthesize the latter. Among the possible structural configurations resulting from the partially occupied oxygen site in the superstructure phase, the most stable structure has a space group , reduced from that of the simple tetragonal structure P4/mmm. The detailed analysis of the electronic band structures of the simple tetragonal and superstructure phases suggests that the out-of-plane buckling of the O atoms in the superstructure leads to significant decrease in the O pCu d orbital overlap, allowing the energy of the system to be lowered, which is necessary for the structural stability. An understanding of the electronic structure and energetics of the high-pressure superstructure phase and its relation to the simple tetragonal phase provides a basis for exploring the physical properties of the infinite layer, high-TC superconductor. © 2011 IOP Publishing Ltd.

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Journal of Physics Condensed Matter