Systematic Study of the Thermal Properties of Zeolitic Frameworks

Abstract

We report a systematic study of the thermal and mechanical properties of 134 pure\nSiO2 zeolites through DFT-based calculations by making use of the quasi-harmonic\napproximation (out of a total of 242 known fully ordered zeolitic frameworks). The\ncomparison of our results with reported experimental data for several zeolites revealed\na very good accuracy and validated our simulation methodology. We observe a wide\nrange of thermal expansion coefficients (from −5 to −35 MK−1), highlighting the great\ninfluence of the framework topology over this physical property, while demonstrating\nthat all pure-silica zeolites exhibit negative thermal expansion (NTE). Our simulations\nalso provide a path for the computation of the bulk modulus for each structure, as\nwell as its pressure and temperature dependence. Results revealed a large gamut of\nbulk modulus values (from 8 to 134 GPa), showing that most frameworks display\npressure-induced softening — but not all! Finally, this study provides some hints to\nthe open question of experimental feasibility of zeolitic frameworks, showing that the\nexperimentally synthesized structures appear to have a distinct distribution of thermal\nand mechanical properties.