Molecular Transport in Nanostructured Materials: a Hierarchical Approach to Design Nanostructured Materials
Nano-porous carbon (NPC) structures have structural properties allowing effective application as gas separation membranes and catalytic membrane reactors. Specifically, high selectivity has been observed for separation of O2/N2 (30:1), He/N2 (178:1) and H2/N2 (333:1). The molecular mechanism of separation on NPC are not yet fully understood. For example, in the case of O2/N2, conventional wisdom has it that the separation is kinetic, based on small geometric differences between the molecules. However, recent analyses of permeation data on NPC's via Transition State Theory do not support this mechanism. Rather, it is postulated that the enthalpy of the transition state is responsible. Hence, models for activated transport in NPC's must focus on the use of accurate interaction potential functions, such as those afforded by ab initio methods.
Goals & Expected Results
"The goal of this project is to provide a predictive, coherent theoretical description of configurational diffusion from first principles. A novel, hierarchical approach will connect ab initio quantum mechanical calculations to mesoscopic diffusivities and thermodynamic solubilities. Specific applications to be considered include gas separation in NPC's and permeation through polymers confined in mesoporous silica. The results will have application in a wide range of technologies, but most specifically for the rational design of membranes used in separation processes"
Hierarchical Approach and Task Plan
Information Flow: Computational quantum mechanics will be used as a basis for new and more accurate potential functions, which in turn can be used to produce far more realistic Monte Carlo and molecular dynamics simulations than are presently possible. The analysis of the trajectories provides short time diffusivities and establishes the transition state geometries. Both results can be extended to macroscopic length scales and to longer times via both generalized hydrodynamics and transition state theory.
Scientific investigation of diffusion using computer modeling will motivate new experimental investigations, i.e.
Current Areas of Active Research