Mobility of alkali metal ions in alkali-borate glasses: A quantum-chemical studyстатья
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Дата последнего поиска статьи во внешних источниках: 18 июля 2013 г.
Аннотация:Various types of motion of metal cations in alkali-borate glasses are considered in the framework of the cluster approach using the half-empirical MNDO method. In neutral systems, cation M+ is coordinated predominantly to edges of the BO4- tetrahedron; it is localized on the outer side of the corner fragments B-O-B and can easily change its position. When in the vicinity of a pentaborate group, M+ executes a complete rotation without spending much energy; in tetraborates, oscillations are possible, with the rotation angle changing in the interval 180 degrees to 270 degrees; only near triborate, one position is more stable than others. The cation may migrate from one center to another along chains of the continuous network of the glass on the outer side of the corner fragments B-O-B. In nodes corresponding to pentaborate and tetraborate centers, the cation may pass onto another chain and change its direction.