One possibility of determining the parameters of the substitutional impurity model from low-temperature data

The root-mean-square displacements of a substitutional impurity in an fcc crystal are calculated with allowance for changes in the interaction of the impurity with its immediate neighborhood (α bonds) and between the atoms of the matrix lattice in the first coordination sphere around the impurity atom (β bonds). The impurity concentration is low. The calculations are performed for the nearest-neighbor interaction model in the harmonic approximation. The rms displacements are shown to be more sensitive to α bonds than to β bonds. The magnitudes of the α and β bonds can be determined by using data from low-temperature measurements of the rms displacements and the heat capacity of a solid solution.