Mainly ruled by oxygen octahedral rotations, perovskite oxides can exhibit zone boundary transitions (ZBTs) either with $d{T}_c/dP>0$ or $d{T}_c/dP<0$. Synchrotron structural investigations at high pressure conditions place $\mathrm{YA}{\mathrm{l}}_{0.25}\mathrm{C}{\mathrm{r}}_{0.75}{\mathrm{O}}_3$ orthorhombic perovskite at the boundary of ZBTs. The absence of changes in the octahedral tilting and a volume reduction with pressure exclusively controlled by an isotropic polyhedral compression set $\mathrm{YA}{\mathrm{l}}_{0.25}\mathrm{C}{\mathrm{r}}_{0.75}{\mathrm{O}}_3$ as the first finding of a possible asymptote at the Clapeyron relation for predicting ZBTs in perovskites. Furthermore, the discovery of a “locked-tilt perovskite” can pave the way to a new class of functional materials.

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• Elastic modulus
• Phase transitions
• Pressure effects
• Crystal structures
• Perovskites
• Polycrystalline materials
• Pressure techniques
• X-ray powder diffraction