High-pressure neutron-diffraction study of the metallization process in PrNi<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">O</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>

The modifications of the crystallographic and magnetic structures of PrNi${\mathrm{O}}_{3}$ associated with the decrease of the metal-insulator transition temperature, ${T}_{\mathrm{MI}}$, with external pressure (${P}_{\mathrm{ext}}\ensuremath{\approx}5$ kbar) have been investigated by means of neutron powder diffraction. Our results indicate that the symmetry of the unit cell (orthorhombic $\mathrm{Pbnm}$ at ambient pressure), is preserved in the pressure range studied. The changes observed in the Ni-O distance and the Ni-O-Ni superexchange angle are, however, similar in sign but very different in magnitude from those obtained by applying an equivalent "internal" pressure. The antiferromagnetic ordering observed at ambient pressure for $T&lt;{T}_{\mathrm{MI}}$ remains unchanged for ${P}_{\mathrm{ext}}&lt;5$ kbar. This finding is in strong contrast with the results of high-pressure electrical resistance measurements, where a reentrant metallic behavior was observed for $P&gt;4$ kbar and $T&lt;65$ K.