ATOM-SPECIFIC THERMAL VIBRATION AMPLITUDES IN STOICHIOMETRIC NIAL - AGREEMENT OF NEUTRON-DIFFRACTION AND AB INITIO-BASED MOLECULAR-DYNAMICS

The use of Rietveld refinement using powder neutron diffraction data p rovides a unique means to measure the atom-species-specific mean squar e thermal displacements; while molecular dynamics (MD) using ab initio -based atomistic potentials provides a means of calculating predictive ly these same quantities without any fitting or use of experimental da ta whatsoever. In this paper application of this neutron-diffraction-b ased technique to a metallic system is reported for the first time and it is found that the differences in thermal amplitudes for Ni and Al are in close agreement with our ab initio-based MD predictions, and th at absolute values are about a third greater.