Generalized anisotropic planar rotor model and its application to polymer intercalation compounds

A diverse structural phase progression is observed in diffraction studies o f an alkali-metal intercalated conducting polymer, poly(p-phenylene vinylen e), as functions of both temperature and chemical potential. Despite the pr esence of translational displacements, extensive disorder, and other experi mental host limitations, an equivalent heuristic structural counterpart app ears in a phase diagram derived using a modified anisotropic planar rotor H amiltonian (introduced and studied by Choi, Harris, and Mele). This model i ncludes only rotational motions and therefore demonstrates that much of the underlying structural evolution is governed by only a few key degrees of f reedom.