Systematic Study Of The Thermal Properties Of Zeolitic Frameworks

We report a systematic study of the thermal and mechanical properties of 134 pure SiO2 zeolites through density functional theory-based calculations by making use of the quasi-harmonic approximation (out of a total of 242 known fully ordered zeolitic frameworks). The comparison of our results with reported experimental data for several zeolites revealed a very good accuracy and validated our simulation methodology. We observe a wide range of thermal expansion coefficients (from -5 to -35 MK-1), highlighting the great influence of the framework topology over this physical property, while demonstrating that all pure-silica zeolites exhibit negative thermal expansion. Our simulations also provide a path for the computation of the bulk modulus for each structure, as well as its pressure and temperature dependence. Results revealed a large gamut of bulk modulus values (from 8 to 134 GPa), showing that most frameworks display pressure-induced softening.but not all! Finally, this study provides some hints to the open question of experimental feasibility of zeolitic frameworks, showing that the experimentally synthesized structures appear to have a distinct distribution of thermal and mechanical properties.