Figure 3.

a, b) Temperature dependence of strain components for the Pc and P1 structures, as defined with respect to the parent Cc structure. All the strains vary continuously through the Cc→Pc transition at circa 247 K and discontinuously through the Pc→P1 transition at circa 90 K. c) Variations of the square of the intensity, I _k, of the superstructure reflection with hk1=−181, which appears in diffraction patterns from the Pc phase. The data show I _k ²∝(T _c−T), within experimental uncertainty, and T _c=247±2 K.