Development of 3D polymer DFT and its application to molecular transport through a surfactant‐covered interface

Abstract

We have developed a three-dimensional polymer density functional theory (DFT) and applied it to predict the thermodynamic and structural information of molecular transport through a surfactant-covered interface. The green recursive function method has been employed to consider the chain conformation effect. The reference ideal gas method has been developed, extending it from molecular DFT to polymer DFT, with a universal form to calculate thermodynamic properties such as the grand potential and free energy. We have demonstrated the accuracy of the theory by comparing it to available simulations. Furthermore, we have applied the theory to predict the free energy barrier and density profile of molecular transport through a surfactant-covered interface. The free energy profile provides reasonable predictions of the transition velocity, while the density profile gives insight into the microstructural information of the transport process, which is consistent with the available molecular simulations.

Toxicant Deposition and Transport in Alveolus: A Classical Density Functional Prediction

“…We used CDFT to calculate Ω­[ r ,ρ­( r ’)], which is written by where k B is the Boltzmann’s constant, T = 298 K is the temperature, and F ex [ρ­( r )] is the excess free energy function. The density profile ρ­( r ) can be solved iteratively: where β = 1/( k B T ), Λ is the de Broglie wavelength, μ S is chemical potential of the surfactant, V bond ( r ) is the bonding potential of the surfactant chain, and V ext ( r ) is the external potential, which corresponds to the direct interaction between the transport molecule and the surfactant.…”

“…Numerically, V ext ( r ) can be calculated by the summation of eq : where subscript i denotes the i th atom of the transport molecule. The detailed formulas for F ex [ρ­( r )] were introduced in our previous work …”

“…However, because of the low computational efficiency of molecular simulation, its application to molecular transport through pulmonary surfactant is limited. Another promising method is classical density functional theory (CDFT), which has revealed itself as an efficient and robust tool for interfacial systems during the past decades. − The main idea of CDFT is to obtain the density profile by minimizing grand potential or free energy functions and to predict other properties from the density profile. Unlike molecular simulation, there is no sampling in CDFT, and the computational cost is thus much lower than that of molecular simulation, especially for chainlike molecules (the pulmonary surfactant in this work).…”

Molecular Structure Modulated Trap Distribution and Carrier Migration in Fluorinated Epoxy Resin

“…The common theory is quantum theory, and quantum chemical calculation is used to show the structure of the molecules and the interaction between the molecules, helping to predict the electron behavior and figure out the material properties and their internal relationship with the structure. With the development of the framework and numerical methods, the density functional theory (DFT) has become a powerful research tool, for exploring the structural and the transport properties of the polymer material considering the effects of different electric fields [29][30][31][32][33]. However, the physical mechanism of fluorination modulated surface charge behaviors hasn't been revealed from the point of molecular orbital view.…”

Time‐dependent density functional study for nanodroplet coalescence

“…Different from hydrodynamics, TDDFT is based on statistic mechanics, considers molecular interactions, and can be applied to nanoscale systems, which is similar to molecular simulation. During the past decades, the accuracy of TDDFT has been well‐examined from simple geometric systems (such as electric double layers) to 3D structured systems (such as porous materials) . To the best of our knowledge, this theory has not been applied to the coalescence of nanodroplets, which will be implemented in this work.…”