Topological consideration of thallium on glassy arsenous selenide

Understanding of the effect of the addition of Tl on glassy As2Se3 prepared under vacuum, has greatly improved with the advent of several structural a nd chemical models, which predict the influence of such an addition, in ter ms of the average heat of atomization H-s and the average coordination numb er N-co. The latter are computed from the atomization and the coordination number of the elements, respectively. A correlation had been found between the chalcogenide system (As2Se3)(1-x)Tl-x and the number of lone-pair elect rons. The stable vitreous state can be obtained only if enough lone-pair el ectrons exist in the structure of the chalcogenide system. The cation in th e chalcogenide glasses may interact with the lone-pair electrons, of bridgi ng chalcogen atoms and influence the glass forming ability. Investigation o f the dependence of the differential thermal analysis (DTA) and, optical ga p E-g "previously published" on the composition of vacuum prepared (As2Se3) (1-x)Tl-x revealed that the average coordination number N-co, has a great e ffect on these properties. The nature of the N-co dependencies is discussed in relation to topological and percolative consideration. (C) 1999 Elsevie r Science Ltd. All rights reserved.