Atomistic Picture of the Intermediate Phase in GexSe1-x Glasses: A Joint Theoretical and Experimental Study*

Raman and calorimetric studies on~~GexSe1-x glasses have provided evidence for the existence of the intermediate phase (IP) in chalcogenide and other glasses. Here, Ab-initio molecular dynamics (MD) based models of these glasses are discussed, and an atomistic picture of the IP, based upon the models and available experiments, is presented. A thorough analysis of our models reveals that the IP in GexSe1-x glasses appears due to the competition between the percolating~GeSe2 phase~and the a-Se phase, which gives rise to the ``flattening'' of the observables in the IP window. We present X-Ray Absorption Near Edge Structure (XANES) measurements on germanium selenide glasses in the IP composition range, and detect an electronic signature of the IP in terms of the shift of the XANES white line (WL) and non-linear behavior o their intensities in the IP window. We show that these models appear to properly represent the XANES results.