Hole generation of prepeaks in diffraction patterns of glasses

(Received 6 January 1992, accepted in final form 10 March 1992)

Abstract
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.