Classical density functional theory of confined fluids: From getting started to modern applications

The application of classical density functional theory (cDFT) to model confined fluids is an outstanding example of directly using fundamental scientific knowledge, such as Statistical Mechanics, to calculate both structural fluid information and macroscopic physical properties needed for process design. One of the goals of this work is to provide materials that allow the reader to become familiar with cDFT. To do that, we present the fundamentals of cDFT and provide sample computational codes that apply its concepts to simple cases. A second goal is to present some of the modern applications of cDFT and related techniques, such as the multicomponent potential theory of adsorption and the development of specialized equations of state for confined fluids, as well as to review publicly available cDFT computer libraries. Overall, there has been a remarkable number of successful applications, ranging from ideal gases confined in 1D geometries to fluids modeled by modern equations of state in 3D porous solids. At the same time, some challenges remain. For example, most implementations are based on grand-potential formulations, which are not always the most convenient for process design. Further, additional results of heat of adsorption predictions would be useful because of their importance in equipment design. Another intriguing alternative could be integrating information from quantum DFT software simulations as input for classical DFT simulations.