The structural and electronic properties of BiCoO3 under high pressure have been
investigated. Synchrotron X-ray and neutron powder diffraction studies show that the
structure changes from a polar PbTiO3 type to a centrosymmetric GdFeO3 type above 3 GPa
with a large volume decrease of 13% at room temperature revealing a spin-state change.
The first-order transition is accompanied by a drop of electrical resistivity. Structural results
show that Co3+ is present in the low spin state at high pressures, but X-ray emission spectra …

Figure 1 shows the XES spectra of Co Kβ emission lines at room temperature at ambient
pressure and at 4.8 GPa. Both spectra show a main peak located at 7650 eV, referred to as
the Kβ1, 3 line. At ambient pressure, the XES spectra has a satellite peak at 7037 eV
denoted Kβ'line. On the other hand, the Kβ'is less pronounced in the spectrum at 4.8 GPa.
The Kβ spectra have been interpreted using atomic multiplet calculations. It is widely
accepted that the spectral shape of Kβ emission is dominated by the final state interaction …