Observation of coupling between vibrational and configurational entropy in a supercooled molecular chalcogenide glass-forming liquid

The temperature dependence of the line widths and frequencies of the vibrational modes of As4S3 molecules is studied in the Ge3As52S45 molecular glass and supercooled liquid at temperatures ranging from similar to T-g - 189 K to up to similar to T-g + 111 K, using Raman spectroscopy. The results reveal the presence of strong dynamical coupling between vibrational and configurational degrees of freedom of the molecules such that both the phonon lifetime and the density of states are affected by the rotational (and possibly translational) molecular dynamics in the supercooled liquid. The physical origin of such coupling is discussed within the framework of the potential energy landscape model of the glass transition. (C) 2016 Elsevier B.V. All rights reserved.