Electronic structure and energetics of tetragonal SrCuO2 and its high-pressure superstructure phase

Abstract

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 0.13 eV per SrCuO2 formula unit. The energy barrier to the transition from the superstructure to the simple tetragonal structure is 0.24 eV at 7 GPa; 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 p–Cu 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.