An X-ray investigation of atomic vibrations in cadmium

Measurements are made of the intensities of x-ray reflections from cadmium powder at 86° and 293° K. Absolute values of the ratio I 86 / I 293 are obtained from comparative measurements on a composite specimen of cadmium and aluminium powders. The results are discussed in relation to recent theoretical work regarding the effect of lattice vibrations in hexagonal metals on the intensities of x-ray reflections. It is shown that the lattice vibrations in cadmium are considerably greater parallel to the c axis than in the basal plane. Values are calculated for the mean atomic displacements in different directions in the metal at 86° and 293° K. (see figure 2), and the results are also expressed in terms of characteristic temperatures: Θ 0 (parallel to the c axis) = 107° and Θ 90 (normal to the c axis) = 164 .5 ° K. These results are compared briefly with similar results for zinc and magnesium, and with values obtained from specific-heat measurements.