Correlating structure with non-linear optical properties in xAs₄₀Se₆₀·(1 - X)As₄₀S₆₀ glasses

A series of xAs40Se60·(100 − x)As40S60 glasses, where x = 0, 25, 33, 50, 67, 75 and 100 mol% As40Se60, has been studied using neutron and X-ray total scattering, Raman spectroscopy and 77Se MAS-NMR. The results are presented with measurements of non-linear refractive indices, n2, and densities. There is no evidence for the formation of homopolar bonds in these glasses, but neutron correlation functions suggest that there is a non-random distribution of sulfur and selenium atoms in sulfur-rich glasses. The average number of sulfur atoms at a distance of 3–4 Å from a selenium atom, nSeS, deviates from a linear variation with x in glasses containin