Analysis of the parameters of a smeared orientational transition at 250–260 K in C60 crystals

The orientational structural transformation in C₆₀ crystals at temperatures of 250–260 K is investigated within the theory of smeared first-order phase transitions. The parameters of this transformation are analyzed using the experimental temperature dependences of the heat capacity and the inelastic (ferroelastic) strain rate in the phase transition range. The elementary volume of the transformation (11–83 nm³) in a correlated motion of C₆₀ molecules and the spontaneous shear strain of the lattice (2.4×10^‑2) upon its transformation from the simple cubic to the face-centered cubic structure are determined.