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Abstract

Abstract Radiation modification in network glass formers such as arseno-chalcogenide alloys As–X (X = S, Se) is examined accepting possibilities of volume restrictions in their realization. Destruction of covalent chemical bonds in these alloys under above bandgap light exposure or irradiation is accompanied by their relaxation in a new state. When this process occurs via switching of heteronuclear (As–X) bonds into homonuclear (As–As) and (X–X) ones, like under intrinsic decomposition in As 2 X 3 glass, an additional volume appears resulting in red shift of optical absorption edge. Assuming that double covalent bond-based X = As(X 1/2 ) 3 units are stabilized due to inner pressure in a glass structure caused by nanoconfined geometry, a blue shift in optical absorption edge is expected. This analysis based on quantum-chemical modeling of network-forming atomic clusters clarifies misunderstandings with these X = As(X 1/2 ) 3 units as principal species facilitating self-organization in As–X (X = S, Se) glassy networks. Computing the balance of energetic costs needed for hetero-to-homonuclear bond transition in stoichiometric As 2 X 3 glasses followed by transformation of single covalent bond-based clusters (As 2 X 4 ) into double covalent bond-based structural units X = As(X 1/2 ) 3 , it was confirmed the impossibility of such anomaly in glassy arsenoselenides as compared with arsenosulfides.