Simulation and Software Development to Understand Interactions of Guest Molecules inPorous Materials

The effect of inclusion of explicit polarization is investigated through several theoret- ical studies of crystalline porous materials herein. In addition to the use of Monte Carlo simulation for such studies, a robust molecular dynamics software is presented which is suitable for analyzing time dependent properties of gases or other molecules in porous materials and other condensed phase systems. Metal-organic frameworks (MOFs) are the main focus of the work included here, a relatively young class of materials originally in- troduced in the early 1990s. These are usually three dimensional crystalline nanoporous materials that exhibit unique properties such as gas separation, storage and catalysis. They are synthesized by the combination of a metal ion e.g. Cu2+ with an organic linker e.g. benzene dicarboxylate. They are a very popular topic of scientific research due to the diversity in possible structures and manifold utility – finding applications in electron transfer, sensing, drug release etc. Industrially, MOFs like HKUST-1 and others are on the global market for use in gas storage and separation in fuel cell and raw materials processing. These materials are often ideal candidates for computer simulation owing to their crystalline nature – a very large atomic system (that is, moles of particles) can be under- stood by only evaluating one or a few unit cells of the MOF, usually less than 5,000 atoms, and macroscopic properties such as gas sorption capacity and diffusion coefficients can be calculated through extrapolation of atomistic interactions in a mathematically infinite lattice. The software developed by the space group as of 2005, Massively Parallel Monte Carlo (MPMC), allows for sophisticated calculation of repulsion dispersion, electrostatic and polarization energies. In this work, Monte Carlo Molecular Dynamics (MCMD) is in- troduced, which can hybridize both methods to explore the phase space of a system with ease and better efficiency, as well as explore the effects of MOF flexibility and dynamic properties which to-date are rarely studied. Studies involving primarily CO2, H2 and CH4 will be presented, but other gases investigated include C2 H2 , C2 H4 , C2 H6 , N2 , H2 O and others. Metal-organic materials with a wide variety of composition and structure will also be presented. Finally, features of the software MCMD will be presented for use by future studies