Hole generation of prepeaks in diffraction patterns of glasses

Overview & Synopsis

It is shown that most of the covalent glass atomic structures can be derived from the Dense Random Packing of Hard Spheres (D.R.P.H.S.) model by introducing successively a series of inflated subnetworks consisting of holes. From this point of view the so called First Sharp Diffraction Peak (F.S.D.P.) of their diffraction pattern appears as a hole generated prepeak of the 1 st neighbor component of the D.R.P.H.S. Structure Factor. The various Medium Range Order (M.R.O.) features which can modulate the prepeak characteristics are reviewed : local topology, network relaxation, chemical ordering, homogeneity. A tentative relationship is made between prepeak behavior and physical property variation with a special emphasis on the optical absorption spectra of covalent glasses.