Structure and Rheology of Se-I Glasses and Supercooled Liquids

Abstract The structural evolution and shear relaxation behavior of binary Se100-xIx (0 ≤ x ≤ 3) glasses and supercooled liquids are investigated using Raman spectroscopy and parallel plate rheometry, respectively. The spectroscopic results indicate cleavage and termination of Se polymeric chains by I atoms via the formation of Se-I bonds, leading to shortening of the average chain length with progressive addition of I atoms. Moreover, at I contents of ≥ 2%, a fraction of the I atoms forms I2 dimers. The results from rheometry demonstrate that the structural relaxation rates associated with the fast segmental chain motion and the slow bond scission/renewal dynamics in Se100-xIx liquids increase upon addition of I, with the shortening of the chain length. The increased configurational degrees of freedom of shorter selenium chains leads to a decrease in the isothermal viscosity, Tg and the packing efficiency and an increase in fragility in liquids with higher I content.