A density functional study of sodalite: a new view on an old system

We have conducted a first principles calculation of sodalite (Na8Cl2Al6Si6O24) to explore the structural properties of aluminosilicate frameworks. By isolating Al-poor and rich frameworks, with and without extra-framework ions, we show that framework interaction with extra-framework ions is not the origin of the so-called framework collapse – as previously believed. Instead, this collapse is a direct consequence of framework stresses resulting from aluminum substitution. We find that extra-framework ions play only a weak role in determining the structural configuration of sodalite – a new result that should apply to open zeolite structures in general.