Molecular dynamics simulation of reconstructive phase transitions on an anhydrous zeolite

Abstract

The structural transformation of a framework aluminosilicate, $\mathrm{Li}\text{\ensuremath{-}}\mathrm{ABW}$, is studied using molecular dynamics. The calculations are carried out by applying the method presented by Marto\ifmmode \check{n}\else \v{n}\fi{}\'ak et al. [Phys. Rev. Lett. 90, 075503 (2003)], that allows for the exploration of the Gibbs free energy as a function of the cell parameters by history-dependent dynamics. We show that this technique allows for an extensive exploration of the phase space also for complex polyatomic material, such as a zeolite, and allows for the successful prediction of a reconstructive phase transition at the pressure and temperature of experimental relevance. In particular, we observe a reconstructive transition from anhydrous $\mathrm{Li}\text{\ensuremath{-}}\mathrm{ABW}$ to eucryptite at the temperature of $\ensuremath{\sim}920\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, as experimentally observed. The steps initiating the transformation and the transition pathway are discussed.