Network structure and property evolution of GexAsySe1-x-y glasses: towards specialized functional glasses

Abstract

The structure and property evolution of Ge_xAs_ySe_1-x-y glasses was finely modelled for exploring specialized functional materials. Raman spectra described the network structure evolution induced by changes in the compositions. The bonding probabilities of Ge-Ge and As-As bonds are highly similar, as inferred from the observed broadening and shifting of their Raman characteristic peaks. Following this deduction, the chemical bond distributions of the GeAsSe glasses were calculated. Further, the cohesion energy and the mean bond energy were also calculated. The refractive index, glass transition temperature (T_g), coefficient of thermal expansion (CTE), thermo-optical coefficient (dn/dT) and Vickers hardness were all well modelled with mean coordination number (MCN). Refractive index transition was found around MCN = 2.6 for the compositions with variable Ge content and fixed As content. The slope of the increase in refractive index seems to have a transition at MCN = 2.4. These two transitions are correlated to the structural transitions of floppy to isostatically rigid and isostatically rigid to stress-rigid. Further, a series of molar refractivity and bond refractivity were computed by multiple linear regression. It will facilitate a quick evaluation of other GeAsSe glasses. Otherwise, higher T_g corresponds to compositions closer to standard stoichiometric ratio when MCN remains constant. Negative dn/dT was observed in compositions with larger CTE and smaller MCN (MCN < 2.4). These detailed property evolution patterns and computational solutions will facilitate the investigation of specialized functional or tailored materials.