The paraelastic-to-ferroelastic phase transition in the lithium vanadium oxide bronze ∊ʹ-Li0.527V2O5 was studied by low-temperature, high-resolution Guinier diffractometry. At the transition the symmetry changes from orthorhombic Pmmn to monoclinic P21m11 at Tc = 285(5) K. At all temperatures anisotropic broadening of the reflections occurs, indicating the presence of stacking faults in this layer structure. X-ray intensity calculations in terms of a one-dimensional model of stacking disorder were carried out in order to elucidate the structural changes induced by the phase transition, and to determine the critical behaviour of the order parameter Q. The symmetry relations between the Pmmn and P21m11 phases allow the development of the spontaneous strain which is, in this system, proportional to the change in cos α. A bilinear coupling between es and Q was found.
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