Analysis of disordered materials using total scattering and the atomic pair distribution function

The total scattering approach and the PDF technique allow one to obtain a picture of the "true" atomic structure from a variety of materials from glasses to crystalline disordered materials, multi phase systems containing amorphous and crystalline components as well as nanoparticles. In all of these cases, the study of the PDF adds important structural information or makes a structure determination possible at all. Great advances have been made to allow the rapid and straight forward collection of total scattering data. In case of neutron scattering, the instrument NPDF at the Lujan Neutron Scattering Center is at the forefront of these efforts. For a standard sample, the structure function, S(Q), as well as the PDF, G(r), are automatically generated and accessible to the instrument user via a web site. The true challenge is the understanding and modelling of the structure of complex systems. A very simple approach was demonstrated in the section about domain structures. The ultimate goal would be to construct a sufficiently large model structure consisting of the matrix structure, the domains as well as a structural description of the domain boundary. Although in principle possible, this is currently still very much at the limit of what is possible with today's programs and available computing power. However, current efforts focus on the development of better and more user friendly modeling software. There is no doubt, at least in the author's mind, that the PDF technique will continue to grow and become the structural tool of choice to study complex materials.