Restructuring of MFI Framework Zeolite Models and Their Associated Artifacts in Density Functional Theory Calculations

Abstract

This study compares and evaluates multiple orthorhombic silicalite MFI framework structures using periodic density functional theory (DFT) calculations implemented with a wide range of exchange–correlation functionals and dispersion-correction schemes. Optimization of the structure available from the International Zeolite Association (IZA) yields only metastable forms, which restructure to arrangements 18–156 kJ mol–1 lower in energy (55 kJ mol–1 on average) through annealing and adsorption/desorption processes without altering their connectivity. These restructuring events can occur unintentionally during DFT studies of adsorptive and catalytic properties, leading to very large artifacts in DFT-predicted adsorption, reaction, and activation energies. Pre-annealing the IZA structure prevents restructuring and these artifacts but forms MFI structures which do not conform to the Pnma spacegroup symmetry and have significantly perturbed sinusoidal and straight channel geometries. These issues persist across ...