Group theory is used to define complete force fields for deltahedral and trivalent molecular skeletons in terms of bond stretches, and bond stretches and slides, respectively. Analysis of ab initio Hessian matrices shows the delocalized nature of the force field in boranes and the relatively localized force field in C-60, where only interactions of bonds in adjacent rings or separated by at most three edges of the truncated icosahedron show significant interaction.