Amorphous chalcogenides are characterized by unique properties such as electric switching, reversible amorphous-to-crystalline transition, or high infrared transmittance. Technologies based on chalcogenide glasses are successfully applied in optical data storage, optical telecommunication, or radiometry, for example. Due to the short crystallization time, excellent reversibility between the amorphous and crystalline states, and high thermal stability, Ge-Sb-Te alloys are the best materials for rewritable optical memories at present. As-S and As-Se chalcogenide glasses with additions of Ag or AgI are currently investigated in relation to practical applications in lithography, diffractive optical gratings, optical and electrical switchers, and sensitive electrochemical electrodes.

In this lecture, we consider atomic ordering phenomena in multicomponent chalcogenide glasses on the short and medium range scale. It will be shown, which information can be extracted directly from the x-ray diffraction, neutron diffraction and extended X-ray absorption spectroscopy measurements, and which difficulties arise due to the multicomponent constitution of alloys. It will be demonstrated, how the information on local atomic structure in terms of the partial pair distribution functions, mean interatomic distances and coordination numbers can be obtained by the reverse Monte-Carlo structure modeling.