Experimental Determination of Partial and Environmental Structure Functions in Non-crystalline Systems — Fundamental Aspects

Abstract

All atomic positions in crystalline materials are described by means of a few parameters of distance and angle. However, such a simple definition is impossible in non-crystalline systems such as liquids and glasses, because of the lack of long-range structure periodicity. However, the atomic-scale structure of non-crystalline systems can be described quantitatively in terms of the so-called radial distribution function (RDF), which indicates the average probability of finding another atom within a specified volume at a distance from an origin atom as a function of the radial distance. The RDF information gives spherically averaged information on the atomic correlation as one-dimensional data; however, it provides unique quantitative information for describing the structure without long-range periodicity. In other words, the method is somewhat limited for describing the structure of non-crystalline systems. The description of the principles and the utility of the RDF has already been published in detail (see, for example, [1, 2]); so here we introduce the essential points of the RDF analysis of non-crystalline systems for the convenience of discussion.