Pressure-induced phase transitions in Co₃O₄: a first-principles study

Co₃O₄ is an important transition-metal oxide with wide applications in catalysis and energy storage. In this work, using evolutionary ab initio structural searches combined with first-principles calculations, we systematically investigated its structural stability, phase transitions, magnetic evolution and electronic properties within the pressure range of 0-100 GPa. Our results show that the cubic Fd3̄m phase first transforms into an orthorhombic Fddd structure through a symmetry-lowering distortion driven by compressibility mismatch between Co²⁺O₄ and Co³⁺O₆ polyhedra. Pressure-enhanced Co-O hybridization and broadened 3d bandwidth modify the exchange interactions, driving the magnetic ground state from antiferromagnetic (Fd3̄m) to ferromagnetic (Fddd). A subsequent first-order transition to a monoclinic P2₁/c phase involves full CoO₆ coordination, lattice densification, and charge redistribution between Co²⁺ and Co³⁺, ultimately leading to magnetic collapse. Based on these results, a detailed temperature-pressure phase diagram is constructed. These findings not only elucidate the intrinsic coupling among the crystal structure, coordination environment, and magnetism in Co₃O₄ under high pressure but also provide insight into phase transitions in spinel-type transition-metal oxides.