Per-axis, per-polymorph instantaneous thermal expansion coefficients for PbTiO3, KNN, GaMo4Se8 and the ferrierite control, extracted from COD multi-temperature CIFs. Source for the transition-ladder atlas post.
How a phase transition bends thermal expansion: an atlas from COD multi-temperature series
PbTiO3, KNN, GaMo4Se8 and a ferrierite control from COD multi-T CIFs: transition anomalies carry single-axis dominance and transition-anchored alpha(T) curvature; framework NTE is sign-coherent and linear. Family controls CaTiO3/BiFeO3 close the "orthorhombic perovskites just do that" objection.