Monte Carlo models of atomic arrangements in arsenic-selenium glasses

• Published in: Journal of non-crystalline solids 1974-01, Vol.16 (1), p.1-14
• Main Authors: Renninger, A.L., Rechtin, M.D., Averbach, B.L.
• Format: Article
• Language: English
• ISSN: 0022-3093; 1873-4812
• DOI: 10.1016/0022-3093(74)90064-7

Models of the atomic arrangements for a series of bulk AsSe glasses with compositions from Se to 50 at % As50 at % Se have been developed using a computer-generated Monte Carlo procedure in conjunction with atomic radial distribution functions. These models demonstrate the gradual growth of interconnected chains from a mixture of chains and rings in pure selenium up to 40 at % As followed by a gradual breakdown of such structures. This behavior correlates well with a number of properties dependent on molecular morphology such as the glass transition temperature, viscosity, electric conductivity and photoconductivity. The models indicate that the mean Se vertex bond angle is about 104° with an rms deviation of 13.5° while the mean As vertex bond angle is 102° with an rms deviation of 15°. An addition model based on the crystalline As 2Se 3 structure has been developed for 40 at % As60 at % Se. It indicates that distortion of the crystalline layer structure must involve breaking about 1 3 of the AsSe rings but that no joining of layers is required. Models were also developed for sputtered films of these materials. Qualitatively, the models are very similar to those for bulk materials, showing rings in pure selenium, gradual interconnection of rings and chains to 40 at % As and then a breakdown of the network above 40 at % As. However there is an increase in the distribution of near neighbor distances and bond angles, some increase in the mean bond angle and at 40 at % As and above, a decrease in the mean near-neighbor distance. Below 40 at % As mean near-neighbor distances for film and bulk materials are the same.