The role of conformational defects in solid-solid phase transitions

B. Bassetti , V. Benza , P. Jona

The role of conformational disorder in solid-solid phase transitions of linear chain molecules (n-alkanes) arranged in a layer is studied in terms of a hamiltonian model. We define a new kind of chain coordinates appropriate to regimes with low conformational disorder. By performing an exact summation over such coordinates, we obtain the effective Hamiltonian describing the interchain interaction within the layer. Assuming, on a phenomenological basis, the existence of two zero temperature crystal structures (orthorhombic or monoclinic-triclinic), we show that only for the orthorhombic one, the coupling between conformational and lattice degrees of freedom results in a rotary phase. We study the mean values of the conformational defects in the different phases of the system.

Mots clés: organic compounds; solid state phase transformations

Domaines: Articles anciens

B. Bassetti, V. Benza, P. Jona. The role of conformational defects in solid-solid phase transitions. Journal de Physique, 1990, 51 (3), pp.259-275. ⟨10.1051/jphys:01990005103025900⟩. ⟨jpa-00212366⟩