Modeling Relaxation Dynamics of Confined Fluids: From Capillary Transitions to Nanoscale Separations

知识价值。这项纳米相关的提案要求支持开发和应用统一的理论方法来研究多孔材料中流体的热力学和动力学。这种统一的建模框架预计将对新型多孔材料的材料科学和工程产生重大影响，它们的应用范围广泛，从催化、吸附和膜分离，到微电子中的低k介电体，再到生物技术中的传感器和诊断。动态平均场论（DMFT）与经典密度泛函理论（DFT）所描述的受限流体热力学完全一致。利用DMFT，人们可以采用与散装流体接触的多孔材料模型，并研究系统对散装状态（化学势或压力）阶跃变化的响应。系统演化到一个最终状态，其中密度分布也是系统的DFT解。该理论可以描述复杂孔隙网络结构的吸附/解吸动力学，包括孔隙冷凝和蒸发的成核机制，以及空化或孔隙阻塞的动力学。该理论也可以应用于混合物，研究诸如混合物的毛细凝聚动力学或多孔材料中一种物质被另一种物质置换的动力学等现象。该研究项目有可能对多孔材料中流体的建模做出革命性的贡献。该项目有三个组成部分：i)用于孔隙网络流体的DMFT。我们将研究孔隙冷凝/蒸发的机制以及孔隙网络中流体的空化现象。我们还将研究部分湿润和部分干燥系统，并将其应用于碳材料中的水的冷凝和汞孔隙率测定；ii)流体混合物的DMFT。我们将研究二元混合物的孔隙凝聚，包括孔隙网络结构和混合物非理想性的影响。我们还将考虑驱替过程的动力学，例如煤层气的提高采收率；iii) DMFT的进一步理论发展和评估。研究人员将通过与非平衡分子动力学和川崎动力学模拟的比较来测试DMFT的准确性。研究人员还将研究成核过程动力学中对称破缺的起源。他们将研究DMFT中波动的显式包含，并将考虑高阶近似的效用。更广泛的影响。虽然这里提出的研究本质上是基础性的，但对多孔材料应用的潜在影响是重大的，并影响到许多技术。在材料科学和新型多孔材料工程方面，世界范围内有巨大的努力，DMFT为理解此类系统中流体的动力学行为提供了新的方法，这与DFT的热力学处理是一致的。这项研究具有变革性，因为它提供了一种在统一背景下处理热力学和弛豫动力学的受限流体特性建模方法。该研究将有助于在受限流体性质领域的两个研究团体之间建立桥梁，一个专注于吸附等温线测量和热力学，另一个专注于输运现象。该项目包括重要的教育和推广计划，包括为社区和四年制州立大学的学生创造本科生研究机会，包括REU，以及加强年轻研究人员参与PI组织的国际会议。该项目还包括与工业界（Quantachrome）和国际合作（莱比锡大学）的合作。

Intellectual Merit. This nano-related proposal requests support for development and application of a unifiedtheoretical approach to the thermodynamics and dynamics for fluids confined in porousmaterials. This unified modeling framework is expected to have major impact upon the materialsscience and engineering of new porous materials and their use is many applications, rangingfrom catalysis, adsorption and membrane separations, to low-k dielectrics in microelectronics, tosensors and diagnostics in biotechnology. The theory being developed, dynamic mean fieldtheory (DMFT), is fully consistent with the thermodynamics of confined fluids as described byclassical density functional theory (DFT). With DMFT one can take a model porous material incontact with a bulk fluid and investigate the response of system to step changes in the bulkstate (chemical potential or pressure). The system evolves to a final state in which the densitydistribution is also a solution of DFT for the system. The theory can describeadsorption/desorption dynamics for complex pore network structures, including the nucleationmechanisms for pore condensation and evaporation, as well as the dynamics of cavitation orpore blocking. The theory can also be applied to mixtures, to study phenomena such as thedynamics of capillary condensation of mixtures or the dynamics of the displacement of onespecies in a porous material by another. The research project has the potential to be atransformative 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 studythe mechanism for pore condensation/evaporation as well as cavitation for fluids in porenetworks We will also study partial wetting and partial drying systems with applications tocondensation of water in carbon materials and to mercury porosimetry; ii) DMFT for fluidmixtures. We will study pore condensation of binary mixtures, including the effect of porenetwork structures and nonideality in the mixtures. We will also consider dynamics ofdisplacement processes such as in enhanced coalbed recovery of methane; iii) Furthertheoretical development and assessment of DMFT. The investigators will test the accuracy of DMFT throughcomparison with non-equilibrium molecular dynamics and Kawasaki dynamics simulations. The investigatorswill 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 ofhigher order approximations.Broader Impacts. While the research proposed here is fundamental in nature the potentialimpact upon applications of porous materials is significant and affects many technologies. There is an enormous worldwideeffort on the materials science and engineering of new porous materials and DMFT provides anew approach to understanding the dynamical behavior of fluids confined in such systems thatis consistent with the thermodynamic treatment from DFT. The research is transformativebecause it provides an approach to modeling confined fluids properties that treatsthermodynamics and relaxation dynamics in a unified context. The research will help bridge tworesearch communities in the area of confined fluid properties, one focused on adsorptionisotherm measurements and thermodynamics and the other focused on transport phenomena...The project includes significant education and outreach programs including creatingundergraduate research opportunities, including REU for students from community and four yearstate colleges and enhancing the involvement of young researchers in internationalconferences the PI is organizing. The project also includes collaboration with industry(Quantachrome) and international collaboration (University of Leipzig).