Noncrystal ionic model for silica glass

A m odel was co nstru cted of p entagon al rin gs o f sy mm et ric al tet ra hedra so co nn ected t ha t all fiy e silico ns li e in one plane and all angles Si-O-Si app rox imate 180. From an ini tial tet rahedro n t he rings extend in six direction s to include its six edges and in t he r es ul t in g t hree-dim ensional network ea ch rin g forms a commo n in te rface b e t,~ee n d od eca hedral cages w hi ch necessar il}: ha ve fiv efold symmetry , Such sy mmetry is in co mpat ible WI th formatJOll of a cryst al lattIC e and t hu s t he stru cture can be exte nded in t hree dimensio ns only to a very limi ted deg ree and wi th unavoidable stress and distor tional s t rain , A stressed net work clu ste r of s uch dodecahedral cages is here called a Vl'I' R ON ,