Polyhedral isomerizations degenerate

Consider a polyhedral isomerization sequence P, rp2 S3 in which Pi and are combinatorially equivalent. Such a polyhedral isomerization sequence may be called a degenerate polyhedral isomerization with Pj as the intermediate polyhedron. Structures undergoing such degenerate isomerization processes are often called fluxional. A degenerate polyhedral isomerization with a planar intermediate polyhedron (actually a polygon) may be called a planar polyhedral isomerization. The simplest... 

The role of polyhedra in the static description of chemical structures makes of considerable interest their dynamic properties. In this connection the central concept in the study of polyhedral dynamics is that of a polyhedral isomerization. In this context a polyhedral isomerization is defined as a deformation of a specific polyhedron Vi until its vertices define a new polyhedron V2. Of particular interest are sequences of two polyhedral isomerization steps Vi V2 V3 in which the final polyhedron V3 is combinatorially equivalent to the initial polyhedron V although with some permutation of the vertices. Such polyhedral isomerization sequences are called degenerate polyhedral iso-merizations. 

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