Development of dual-model classical density functional theory and its application to gas adsorption in porous materials

Classical density functional theory (CDFT) is a useful theory in many fields. The basis of CDFT is spherical model and extending it to nonspherical molecules is a challenging issue due to the orientation/configuration of the molecules, which implies more complicated molecular models, and higher computational costs. In this work, we propose a dual-model classical density functional theory (DM-CDFT) to address this issue. The theory uses a more precise model (all-atom model) and a simpler model (coarsening model) to construct the external and excess free energy functionals, respectively. By using this methodology, CDFT could handle orientation/configuration effects with low computational costs. The theory is examined by applying it to gas adsorption (such as C2H2/C2H4/C2H6 and toxic gases) in porous materials, and the predicted adsorption isotherms verify the accuracy of the theory. Additionally, the predicted density profile indicates that rotation entropy plays an important role in the adsorption of nonspherical molecules.

Automated summary

Classical density functional theory (CDFT) is a useful theory, but extending it to nonspherical molecules is challenging due to molecular orientation, leading to more complex models and higher computational costs. The proposed dual-model classical density functional theory (DM-CDFT) addresses this issue using a precise model (all-atom model) and a simpler model (coarsening model) to handle orientation effects with low computational costs. The theory is validated by its application to gas adsorption in porous materials, demonstrating accurate predictions of adsorption isotherms and the importance of rotation entropy in adsorption of nonspherical molecules.