Bond-changing structural rearrangement in glassy As3Se7 associated with long-term physical aging
Résumé
Ab initio quantum chemical calculations with RHF/6-311G⁎ basis set are performed to justify destruction-polymerization transformations in glassy g-As3Se7 possible during long-term natural physical aging. It is shown that switching of two double bond; length as m-dashAssingle bondSesingle bondSesingle bondAsdouble bond; length as m-dash bridges into short double bond; length as m-dashAssingle bondSesingle bondAsdouble bond; length as m-dash and long double bond; length as m-dashAssingle bondSesingle bondSesingle bondSesingle bondAsdouble bond; length as m-dash fragments is energetically favorable, testifying thermodynamic possibility for such structural changes. This finding is in good agreement with previous experimental observations for g-As3Se7 performed with Raman scattering, NMR and high-resolution XPS measurements. Simulation data suggest that physical aging in Se-rich As-Se glasses can be treated as a unique cooperative relaxation process accompanied by atomic rearrangement within homopolar single bondSesingle bondSesingle bond bonds incorporated between two neighboring AsSe3/2 pyramids.