Structural characterization for a complex system by obtaining middle-range ordering

Abstract

Middle-range ordering in the range of a few nanometers is of great importance for characterizing the structure of various substances, particularly for describing the structure of a complex system. An attempt has been made to propose a new method for obtaining information including middle-range ordering. In this method, the realistic atomic scale model structure is estimated by fitting both the ordinary interference function and the environmental interference function obtained from the anomalous X-ray scattering (AXS) data with the help of model calculation by applying the reverse Monte Carlo (RMC) simulation technique and then middle-range ordering in the range of a few nanometers can be visualized. The usefulness of the present method has been confirmed by obtaining some interesting structural information, which is not sufficiently represented yet, with respect to a complex system such as GeO 2 glass, amorphous ZrO2 and corrosion products (ferric oxyhydroxides, such as FeOOH) formed on the steel surface. This method would be valuable for materials characterization not only of non-crystalline systems but also of crystalline systems in the variety of states. On the other hand, it should be stressed that the present method for obtaining information including middle-range ordering is not a unique mathematical procedure. Nevertheless, the resultant model structure over the range of a few nanometers is considered, at least to some extent, to meet the necessary conditions for explaining two or three independent experimental data. For this reason, we believe that the method coupled with the RMC simulation technique could be a useful way to obtain a realistic model structure over the range of a few nanometers within the framework of information. It would also seem to be very promising to extend this method to the estimation of middle-range ordering of various systems, so that its validity may be tested on a wider base.