A FORMULATION OF ALCHEMY FOR MATERIALS CONTAINING LIGHT-ELEMENTS

A multivariate formulation of the method ALCHEMI is presented, which avoids the problems arising from delocalisation of x-ray producing events. The method solves for the distributions of the impurity elements on the host sites, and for the delocalisation factor associated with their x-ray signals provided the host element signals can be assumed to be localised. Alternatively, if at least one impurity element's and all but one host element's signals are well localised, the impurity distribution and the delocalisation factor for the remaining host element signal can be found. The formulation is successfully tested on a ternary alloy (Ni-Al-Ti) sample for which the distributions of all the elements present are known to high accuracy from anomalous x-ray diffraction measurements, and in which one host element (Al) has a delocalised signal.