Computational exploration of thermodynamic properties of porous and layered materials

Abstract

In this thesis, ab-initio based force fields were developed for Ar and Xe adsorption in six different MOFs to predict adsorption properties and compare this non-empirical approach to the experimental results and generic force field (FF) simulations. Using three DFT functionals (PBE-D2, vdW-DF, and vdW-DF2) in periodic models of M-MOF-74 (M= Co, Ni, Zn, Mg), ZIF-8 and Cu-BTC, first principles based FFs are derived. Selective separation of contaminants from ambient air is another crucial field since some of those contaminants can be detrimental to health. Moreover, UiO-66 is computationally functionalized with more than 30 functional groups using cluster and periodic systems and binding energies of NH3, H2S, CO2 and H2O are calculated to rank the functionalized UiO-66 materials for selective separation of contaminants in humid air conditions. Finally, the phase stability and transitions of 2-D layered ferroelectric materials, CuInP2Q6 (Q=S, Se), are investigated. The phase transition of CuInP2Se6 is studied using DFT calculations and phonon theory to identify instabilities at zone center and boundaries of the structure while possible spinodal decomposition regions of CuxInyP2S6 are determined with respect to Cu concentration by combining DFT calculations with thermodynamic relations.