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

智力上的功绩。这项与纳米相关的提案要求支持开发和应用一种统一的理论方法来研究限制在多孔材料中的流体的热力学和动力学。这种统一的建模框架有望对新的多孔材料的材料科学和工程产生重大影响，它们的用途广泛，从催化、吸附和膜分离到微电子中的低k介电材料，到生物技术中的传感器和诊断。发展中的动态平均场理论(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，人们可以将模型多孔材料与块体流体接触，并研究系统对块体状态(化学势或压力)阶跃变化的响应。系统演化到最终状态，其中密度分布也是系统的DFT解。该理论可以描述复杂孔道网络结构的吸附/解吸动力学，包括孔道凝结和蒸发的成核机理，以及空化或孔道堵塞的动力学。该理论也可以应用于混合物，研究混合物的毛细冷凝动力学或多孔材料中一种特殊物质被另一种特殊物质置换的动力学现象。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。该项目由三个部分组成：i)孔隙网络中流体的DMFT。我们将研究孔道凝结/蒸发的机理以及孔道中流体的空化。我们还将研究部分润湿和部分干燥系统，并将其应用于碳材料中的水的冷凝和汞的孔隙率测定；ii)流体混合物的DMFT。我们将研究二元混合物的孔道凝聚，包括孔道结构和混合物中的非理想性的影响。我们还将考虑置换过程的动力学，例如在提高煤层甲烷采收率方面；iii)进一步发展和评估DMFT理论。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性破缺的来源。他们将研究DMFT中涨落的显式包含，并将考虑高阶近似的效用。虽然这里提出的研究在本质上是基础性的，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。在材料科学和新的多孔材料工程方面，世界范围内进行了巨大的努力，DMFT提供了一种新的方法来理解限制在这种系统中的流体的动力学行为，这与DFT的热力学处理是一致的。这项研究具有变革性，因为它提供了一种方法来模拟受限流体的性质，在统一的背景下处理热力学和松弛动力学。这项研究将有助于在受限流体性质领域的两个研究社区之间架起桥梁，一个专注于吸附等温线测量和热力学，另一个专注于运输现象……该项目包括重要的教育和推广计划，包括为来自社区和四年制州立大学的学生创造本科生研究机会，以及加强年轻研究人员对国际PI正在组织的国际会议的参与。该项目还包括与业界的合作(Quantachrome)和国际合作(莱比锡大学)。

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).