FeO_s: An Open-Source Framework for Equations of State and Classical Density Functional Theory

Abstract

In this work, we present an open-source software package, referred to as FeOsFramework for Equations of State and Classical Density Functional Theory. FeOs is a collection of interfaces and data types that can be used (1) to implement thermodynamic equations of state and Helmholtz energy functionals for classical density functional theory, and (2) to compute thermodynamic properties of pure substances and mixtures, phase equilibria, and interfacial properties such as surface tensions and adsorption isotherms. The framework is written in the Rust programming language with a complete Python interface and is designed with a focus on usability and extensibility. It is openly available on GitHub (). Equations of state can be implemented in Rust, yielding performant code, or as a Python class, which is useful for prototyping and with less emphasis on execution speed. In both cases, the user has to implement a single function: the Helmholtz energy. FeOs then uses generalized (hyper-) dual numbers to evaluate the Helmholtz energy as well as the required exact partial (higher-order) derivatives. Using this type of automatic differentiation delivers performance without the need for implementing any analytical derivatives. The performance is further enhanced by a caching mechanism that avoids duplicate model evaluations. Together with the core interfaces and functionalities for equations of state and classical density functional theory, we provide implementations for multiple models such as the PC-SAFT equation of state (with homo- and heterosegmented group contribution methods) and Helmholtz energy functionals (including segment-based functionals). To showcase a selection of FeOs’ features, an example study of the adsorption of biogas in porous media using the PC-SAFT functional is provided.

Multifidelity Gaussian Processes for Predicting Shear Viscosity over Wide Ranges of Liquid State Points Based on Molecular Dynamics Simulations

“…The full implementation of the method is available on GitHub 67 together with the butanol example and all simulation results. The implementation relies on the PC-SAFT equation of state within the FeOs framework 68 as well as GPy 69 and emukit 70 for the multifidelity model. Column 2 shows the errors obtained from molecular simulations with the TAMie force field.…”

Integrative studies of ionic liquid interface layers: bridging experiments, theoretical models and simulations

“…DFT is another powerful and efficient theoretical tool to model the structuring layers of interfacial ILs and their properties 95 by minimizing the grand potential. 95,96 In general, DFT is developed based on any equation of state (EOS), 97 while for ILs, owing to their complexicity, the EOS based on statistical associating fluid theory (SAFT) is preferred, which have been intensively developed to study the properties of ILs. 98 To present the layering structures and properties of the interfacial ILs, an external potential is needed to consider the strongly assymetruic interactions between ILs and the solid surface.…”

PCP-SAFT Parameters of Pure Substances Using Large Experimental Databases

“…When a substance has a known dipole moment (as obtained from a database), the dipole contribution is simply added when calculating the Helmholtz energy without adjusting an additional parameter. For all calculations, the open-source PCP-SAFT implementation of FeOs (v0.4.3) was used.…”

“…We refer to the Supporting Information for the details of the PCP-SAFT parameters as well as the predicted critical temperature and critical pressure used in this work. With this publication the PCP-SAFT parameters are made publicly available on the FeOs 34 Github repository (https://github. com/feos-org) along with a sample Jupyter notebook for parameter regression.…”