  We study nonlinear vibrational modes of oscillations for tetrahedral
configurations of particles. In the case of tetraphosphorus, the interaction of
atoms is given by bond stretching and van der Waals forces. Using equivariant
gradient degree, we present a full topological classification of the
spatio-temporal symmetries of the periodic solutions. This procedure gives all
the symmetries of the nonlinear vibrations for general force fields.
