A New Structural Study for an Old Quasicrystal

In this paper, we have described the expenmental evidence for the polyhedral order in metastable Al-Mn alloy (icosahedral phase). We have used the anomalous dilfractometry technique to identify the X-ray pattems of this alloy. For the first lime, the radial distribution function of the diffuse rings scattered by this alloy is obtained by applying this new technique. Unlike previous methods used for interpreting the X-ray patterns of this phase, we have introduced a new method of separation for interpreting X-ray pattems. The X-ray diffraction pattem has been nurnerically resilved into a broad diffuse halo and sharp litres. Using finis procedure the correlation position was deduced from a high quality interference function. We have Dot been able to explain either trie origin of the sharp litres or the relationship of the two parts responsible for the fines and rings. In order to explam trie above we need an appropnate geornetrical rnodel and sonne structural information on the rnedium range order of the atorns causing scattered rings. This information is contained in the partial pair-pair correlation function of the coherent background. The result of this work rnay be of aid in order to comprehend the "genetic" relationship between the structure of the crystalline, arnorphous FK phases and this new rnetastable alloy or icosahedral phase.