The stability of (MX)12 cage clusters and cluster-based polymorphs of a large range of alkali halides and the first row element compounds (LiF, BeO, BN and C) were investigated using state-of-the-art plane wave density functional (DF) calculations. Specifically, a nanoporous analogue of the zeolite sodalite (SOD-MX) can be regarded as being assembled from (MX)12 cluster building blocks. For all alkali halides the dense rs-MX phase was found to be more stable than the low-density nanoporous SOD-MX phase. The energy difference between the rs-MX and the SOD-MX bulk polymorphs (per MX unit) was found to increase with increasing ionic radius ratios with the same anion, but at the highest ionic radius ratio the differences decrease. Correspondingly, the cage-based SOD-LiX phases were all found to be only marginally metastable energetically with respect to the rs-LiX forms (ΔESOD-rs≤0.05 eV/LiX). For the first row element compounds, the energy difference between the ground state phases and the SOD-MX bulk polymorphs (per MX unit) was found to increase when consider from LiF to C (ΔESOD-stab=0.05, 0.17, 0.68, 1.07 eV/unit for LiF, BeO, BN and C, respectively). The results of ELF analysis of (MX)12 cage clusters could be explained the difference of electron distribution on each cluster.
Journal: TechConnect Briefs
Volume: 3, Nanotechnology 2009: Biofuels, Renewable Energy, Coatings, Fluidics and Compact Modeling
Published: May 3, 2009
Pages: 304 - 307
Industry sector: Advanced Materials & Manufacturing
Topics: Informatics, Modeling & Simulation