It was recalled that such defects were known to contribute to a decrease, in the elastic moduli of host crystalline solids, via mechanical relaxation. It was proposed here that a different mechanism could occur which changed not only the elastic moduli, but also the corresponding phonon dispersion relationship, via lattice anharmonicity. It took place if the concentration of point defects was high, and their interaction could not be neglected.

T.Suzuki, T.Tonokawa: Japanese Journal of Applied Physics, 1996, 35[1-5B], 3240-3