Morphic effects are effects induced in a crystal by the lowering of its symmetry through the application of a generalized external force. In this paper we study the effects of static electric fields and of strains on the frequencies of localized vibration modes associated with substitutional impurity atoms in homo-polar crystals. It is shown that the splitting of the triple degeneracy of such modes when the impurity is at a site of cubic symmetry by the application of these generalized forces can yield information about the anharmonic forces, electric dipole moment, and electronic polarizability associated with the impurity atom.

• Received 9 December 1966

DOI:https://doi.org/10.1103/PhysRev.163.882