The coordination number calculation from total structure factor measurements

In the structural characterization of amorphous materials, the knowledge of the correlation distances and coordination numbers has a key importance. When several correlation distances overlap in the same diffractogram, obtaining the coordination numbers is a quite difficult task. In this work the method to obtain coordination numbers from total structure factor measurements is described in detail. The procedure is focussed in neutron diffraction experiments, but it is also applicable for X-ray diffraction. In order to illustrate the method, it was chosen as example a chalcogenide glass (Ag25Ge18.75Se56.25)(Ag25Ge18.75Se56.25), a member of a series of ionic conductors that have been studied by neutron diffraction. In particular, the coordination numbers corresponding to the first diffraction peak, involving Ge–Se and Se–Se correlations, are discussed.