Abstract
A theoretical study of the vibrations of a substitutional impurity atom in a host lattice has been performed. The Green's-function method is treated with the purpose of enabling numerical calculations of impurity Green's functions. We consider specifically the host materials silicon, germanium, and -tin, where the phonon dispersion curves are well described by Weber's adiabatic bond-charge model. The concepts of this model are applied to the impurity-host interactions. Numerical calculations are performed for the vibrational amplitudes of the isovalent Mössbauer impurity in the hosts. Comparison with the recent experiments of Petersen et al. shows about 25% force-constant weakenings for in silicon and germanium. Localized mode frequencies for C in silicon and Si in germanium show only 4% force-constant changes.
- Received 19 January 1981
DOI:https://doi.org/10.1103/PhysRevB.25.1225
©1982 American Physical Society