CDFTPY: A python package for performing classical density functional theory calculations for molecular liquids

Classical density functional theory (CDFT) provides a rigorous theoretical framework for the statistical mechanics based analysis of many-body systems. This approach has proven to be successful in simulations of mono-atomic, i.e. simple liquids, and there is an ongoing theoretical effort in extending it to more complex polyatomic, molecular liquid systems. Sharing these developments in the form of open-source and easily accessible codes could greatly benefit these efforts. In this work, we present python-based CDFT code that contains both conventional Reference Interaction Site Model (RISM) and recently developed renormalized site density theory (RSDFT) approach. The current implementation is focused on ion solvation - the problem of both fundamental and practical importance. It allows the calculation of individual ions as well as comparative analysis across a range of interaction parameters. Program summary Program Title: cdftpy CPC Library link to program files: https://doi.org/10.17632/p8dsgz5n4g.1 Developer's repository link: https://github.com/opencdft Licensing provisions: GPLv3 Programming language: python 3.9+ Nature of problem: Computational modeling of molecular liquids at the atomistic level of resolution is an important capability across many scientific areas. Classical density functional theory (CDFT) approaches this problem by building statistical mechanics model of the system in terms of its average atomic (site) density. Such an approach can provide orders of magnitudes improvements in efficiency compared to conventional molecular dynamics simulations, but requires special treatment of multi-scale interactions in a molecular liquid. A practical utility of our open-source python based implementation of CDFT is the study the problem solvation of ions or Lennard-Jones particles. Solution method: Python package developed in this work provides two CDFT implementations for molecular liquids - renormalized site density functional theory and reference interaction site model. It enables calculations of thermodynamic and structural properties related to solvation of spherical solutes. The nonlinear integral equations associated with the two methods are solved iteratively, utilizing Fast Fourier Transform (FFT) for the calculation of the numerically intensive convolution integrals. The resulting code provides near instantaneous evaluation of the solvated properties of individual solutes and high-throughput screening across the range of different solute parameters. (C) 2021 Elsevier B.V. All rights reserved.