On anharmonicity in cadmium

Recent X-ray diffraction data on cadmium [Rossmanith (1978). Acta Cryst. A34, 497-500] have been reanalysed using a temperature factor based on an anharmonic one-particle potential to fourth order for the atoms, and values for the anharmonic parameters have been obtained. The fourth-order parameters α₄₀ and β₂₀ are found not to be significantly different from zero, while the other fourth-order parameter γ₀₀ is found to be strongly correlated to the extinction correction and harmonic parameters. The third-order antisymmetric parameter is found to have a value of 57 ± 16 eV nm^-3, which is in reasonable agreement with a recent measurement. The application of the extinction correction is shown to affect substantially the values for the potential parameters.