Nanoheteromorphous structure and relaxation of glassforming As₂S₃

摘要

The structure of arsenic sulfide As2S3, melting and glass transition process, as well as relaxation of the glass at heating are considered within the concept of polymeric nanoheteromorphous glass structure and glass-forming liquid and its particular case for the individual chemical substance (ICS) - conception of polymeric polymorphoid structure of non-crystalline substance proposed by V. Minaev [1]. ICS in non-crystalline state is a fragment’s copolymer of different structures crystal polymorph modifications (PM), without translational symmetry (long-range order) which is characterized by strictly defined intermediate- and short-range orders inherent to one of the PMs taking part in glass formation. The glass transition process of As2S3 is a twofold process of copolymerization-depolymerization: copolymerization of formed in liquid polymorphoids of high(α)- and low-temperature(β) PM (HTPM and LTPM) and depolymerization of polymorphoids LTPM above Tg (~ 175°C) and HTPM below Tg. Changes in the external conditions of the glass transition process (cooling rate, temperature and time of glass annealing, etc.) are changing the concentration ratio of polymorphoids (CRP) of different PMs. The concentration ratio HTPM:LTPM can be estimated, for example, by comparing the Raman spectra band intensity of glass and crystal HT- and LTPM. CRP is an internal parameter of a thermodynamic system of non-crystalline substance and determines the structure and all properties of substance. A continuum of combinations of the CRP, resulting from changes of external conditions and time, defines the continuum of properties of the non-crystalline substance. This glass is a continuum of metastable states [1].