Anisotropy in the Atomic Vibrations of Zinc Crystals. I. Evidence from X-Ray Scattering

The results of Brindley's recent experiments on the intensity of the various reflections of Cu Kα x-rays from powdered zinc crystals are compared with the results of the measurements made by the authors on the diffuse scattering of x-rays from single zinc crystals. When the method of diffuse scattering is used it is possible to obtain S values for various orientations of the crystal for a given value of (sin1/2φ)λ. The form of Zener's formula for M for hexagonal crystals is confirmed by our experimental results. We find the root-mean-square thermal displacements of the atoms to be 0.172 and 0.093A, respectively, along and perpendicular to the c axis. These are greater than Brindley's values. They nearly explain the large difference between the F values for the (0002) and (101̄0) reflections. These two reflections possibly give some evidence of asymmetry in the electron structure of the zinc atoms, the structure being more diffuse in the direction of the c axis than normal to this direction.