The differential neutron diffraction method using double isotope substitution was applied to determine the Fe-Fe pair correlation function (RDF) in the icosahedral quasicrystalline AlCuFe alloy. Two AlCuFe samples were prepared using different iron (Fe) isotopes, namely 54Fe and 56Fe. Neutron diffraction measurements were performed on each sample, and the difference scattering function was obtained by subtracting the data from one sample from the data from the other. The difference scattering function was then converted to the Fe-Fe RDF.
The obtained Fe-Fe RDF shows a distinct first peak at a distance of about 0.25 nm, which corresponds to the closest distance between Fe atoms. The Fe-Fe RDF also shows a number of other peaks at larger distances, which correspond to correlations between Fe atoms at large distances. The obtained results are consistent with a model in which Fe atoms are arranged in icosahedral clusters. The obtained results provide valuable information about the local atomic structure of icosahedral quasicrystalline alloys.
The study of short-range order in the quasi-crystalline structure of AlCuFe was performed using the method of iron (Fe) isotopic substitution. The aim of the work was to determine pair correlation functions characterizing the radial distribution of atoms. The experiment was carried out on a specialized 7c2 spectrometer installed at the Orphée research center. This spectrometer is optimized for the analysis of local atomic order in disordered systems such as liquids and amorphous materials.
The study yielded highly accurate data on the full radial distribution. The analysis showed that all observed interatomic distances (up to 10 Å) were consistent with the model proposed by Cornier-Quicandon et al. in their 1991 publication. A special feature of the work was the derivation of partial pair correlation functions for Fe-Fe. The results indicate that iron atoms occupy only a certain fraction of the available positions in the crystal lattice.
Author: R. Bellissenta, B. Mozer, Y. Calvayrac, D. Gratias, J. W. Cahn
Institute: Leon Brillouin Laboratory (CEA-CNRS), CE Saclay, F-91191 Gif-sur-Yvette, France, Materials Science and Engineering Laboratory, NIST, Gaithersburg, MD 20899, USA, CECM-CNRS, 15 rue G. Urbain, F-94407 Vitry, France