FOURIER ANALYSIS OF X‐RAY PATTERNS OF SODA‐SILICA GLASS *

Abstract

A bstract X‐ray diffraction patterns were obtained for five compositions of soda‐silica glass. The patterns were made in an evacuated camera, using MoKα radiation monochromated by reflection from rock salt. The patterns show a perfectly continuous change in appearance with increasing soda content. From a Fourier analysis of the X‐ray scattering curves, radial distribution curves for the five glasses were obtained. The distribution curves uniquely establish several important points. Each silicon atom is surrounded by 4 oxygens at a distance of about 1.62A and each sodium by about 6 oxygens at 2.35A. The existence in the glass of simple discrete molecules, such as SiO 2 , NaaO, Na 2 Si2O 6 , and Na 2 SiO 3 , is uniquely ruled out by the distribution curves. The X‐ray results lead to the following picture of soda‐silica glass. Each silicon is tetrahedrally surrounded by 4 oxygens at a distance of about 1.62A. Part of the oxygens are bonded to 2 silicons and part only to 1 silicon. The sodium ions Na + are arranged in various holes in the silicon‐oxygen network, being surrounded on the average by about 6 oxygens at a distance 2.35A. Although this is a definite scheme of structure, it does not repeat identically at regular intervals, and the material, therefore, is noncrystalline.