Measuring correlated atomic motion using X-ray diffraction

The atomic motions in crystals are correlated. In this paper we demonstrate that information about the correlated motion of atoms, and consequently ab out the bonding within the crystal, can be obtained by analyzing the peak w idth of the atomic pair distribution function (PDF). We have measured the P DFs of Ni and InAs using synchrotron X-ray diffraction. The analysis of the Ni data allowed us to determine the Debye temperature which is in good agr eement with values found in the literature. In contrast to the isotropic me tallic bonding in Ni resulting in a relatively weak correlation between the motion of neighboring atoms, we found a very strong correlation in InAs as one might expect from the covalent bond between In and As. The results are compared with theoretical predictions by Chung and Thorpe (Phys. Rev. B 19 77, 55, 1545).