Electronic Properties of Y₂Ba₄Cu₇Oₓ Ceramic via Computational Method

Abstract

Abstract

The structural and normal-state electronic properties of Y₂Ba₄Cu₇Oₓ (Y-247) high-temperature cuprate superconductor were investigated using first-principles density functional theory (DFT). Geometry optimizations were performed based on the experimentally reported orthorhombic structure using the local density approximation (LDA) and the Perdew–Burke–Ernzerhof generalized gradient approximation (GGA-PBE) with ultrasoft pseudopotentials. Both optimized structures preserved the orthorhombic symmetry, while the GGA-PBE results showed slightly better agreement with the selected experimental lattice parameters. Electronic band-structure calculations revealed multiple bands crossing the Fermi level, confirming the metallic character of Y-247 within the conventional DFT framework. The orbital-resolved density of states showed that the electronic states near the Fermi level are predominantly associated with Cu d and O p orbitals, highlighting the important contribution of Cu–O structural units to the electronic behavior of Y-247. Electron-density analysis further elucidated the spatial distribution of charge around these Cu–O units. The calculated energy separations of 1.44 eV and 0.91 eV, respectively correspond to selected electronic transitions above the Fermi level and therefore should not be interpreted as fundamental band gaps or as direct evidence of a superconducting pseudogap. Overall, the present results provide further insight into the structural characteristics and normal-state electronic behavior of Y-247. A more comprehensive description of superconducting pairing and strong Cu 3d electron-correlation effects, however, requires theoretical approaches beyond conventional LDA and GGA.