Basicity or Ionicity – A New Approach for Understanding Glass Properties

Abstract

Basicity of glass is still a challenge in spite of various attempts to measure or calculate it. The values assigned for basicity of glasses, either calculated or experimentally determined, are not always in full agreement with actual facts, and discrepancies among the theoretical ones are not unusual. For instance, SiO2 is described by a single basicity value even if the polymorphs of SiO2 are quite different. Only few attempts were made to face this challenge. Present paper deals with a novel approach on theoretical ionicity / basicity based on electronic energy levels or band structure of solids. Another major adjustment takes into account the possibility of decomposing ionicity of complex chemical bondings into a sum of binary bondings. Considering the distribution of the interbonding angles specific for vitreous systems, it is possible to estimate both a local ionicity (basicity) of bondings and a global (mean) basicity of glass. The variation of basicity (ionicity) with temperature is also presented, this finding being able to open a new view on thermal history of glass considered through chemical character of bondings.