Figure 4. Principal superexchange interaction J_z as a function of the Cu-O-Cu bond angle φ for CuO under high-temperature and high-pressure.

In this figure, P and T are increasing to the right and to the left, respectively. The inset shows the evolution of J_z in CuO as a function of the Cu-O-Cu bond angle φ for CuO under positive and negative pressure, while keeping constant the Cu-O bond length in the CuO₄ plaquettes (d_Cu-O = 1.957 Å).