Ab initio comparison of bonding environments and threshold behavior in Ge(x)As10Se(90-x) and Ge(x)Sb10Se(90-x) glass models

Ab initio models of Ge(x)As10Se(90-x), and Ge(x)Sb10Se(90-x) glasses are constructed, and their bonding environments are characterized and compared against each other and to recent experimental studies of equivalent glasses at the same stoichiometry and density. A minimum in the linear refractive index is found to correlate with a maximum in the number of length-one, predominantly Se, atomic chains for both glass types. The threshold behavior difference between GeAsSe and GeSbSe is shown to be due to the appearance of As-As-Se2 structural units beyond the MCN = 2.67 threshold in the GeAsSe glasses.