Intellectual Merit. This nano-related proposal requests support for development and application of a unified theoretical approach to the thermodynamics and dynamics for fluids confined in porous materials. This unified modeling framework is expected to have major impact upon the materials science and engineering of new porous materials and their use is many applications, ranging from catalysis, adsorption and membrane separations, to low-k dielectrics in microelectronics, to sensors and diagnostics in biotechnology. The theory being developed, dynamic mean field theory (DMFT), is fully consistent with the thermodynamics of confined fluids as described by classical density functional theory (DFT). With DMFT one can take a model porous material in contact with a bulk fluid and investigate the response of system to step changes in the bulk state (chemical potential or pressure). The system evolves to a final state in which the density distribution is also a solution of DFT for the system. The theory can describe adsorption/desorption dynamics for complex pore network structures, including the nucleation mechanisms for pore condensation and evaporation, as well as the dynamics of cavitation or pore blocking. The theory can also be applied to mixtures, to study phenomena such as the dynamics of capillary condensation of mixtures or the dynamics of the displacement of one species in a porous material by another. The research project has the potential to be a transformative contribution to the modeling of fluids confined in porous materials. There are three components to the project: i) DMFT for fluids in pore networks. We will study the mechanism for pore condensation/evaporation as well as cavitation for fluids in pore networks We will also study partial wetting and partial drying systems with applications to condensation of water in carbon materials and to mercury porosimetry; ii) DMFT for fluid mixtures. We will study pore condensation of binary mixtures, including the effect of pore network structures and nonideality in the mixtures. We will also consider dynamics of displacement processes such as in enhanced coalbed recovery of methane; iii) Further theoretical development and assessment of DMFT. The investigators will test the accuracy of DMFT through comparison with non-equilibrium molecular dynamics and Kawasaki dynamics simulations. The investigators will also investigate the origin of symmetry breaking in the dynamics of nucleation processes. They will study the explicit inclusion of fluctuations in DMFT and will also consider the utility of higher order approximations.
Broader Impacts. While the research proposed here is fundamental in nature the potential impact upon applications of porous materials is significant and affects many technologies. There is an enormous worldwide effort on the materials science and engineering of new porous materials and DMFT provides a new approach to understanding the dynamical behavior of fluids confined in such systems that is consistent with the thermodynamic treatment from DFT. The research is transformative because it provides an approach to modeling confined fluids properties that treats thermodynamics and relaxation dynamics in a unified context. The research will help bridge two research communities in the area of confined fluid properties, one focused on adsorption isotherm measurements and thermodynamics and the other focused on transport phenomena. .. The project includes significant education and outreach programs including creating undergraduate research opportunities, including REU for students from community and four year state colleges and enhancing the involvement of young researchers in international conferences the PI is organizing. The project also includes collaboration with industry (Quantachrome) and international collaboration (University of Leipzig).
