MolMod – an open access database of force fields for molecular simulations of fluids

ABSTRACT

The MolMod database is presented, which is openly accessible at http://molmod.boltzmann-zuse.de and contains intermolecular force fields for over 150 pure fluids at present. It was developed and is maintained by the Boltzmann-Zuse Society for Computational Molecular Engineering (BZS). The set of molecular models in the MolMod database provides a coherent framework for molecular simulations of fluids. The molecular models in the MolMod database consist of Lennard-Jones interaction sites, point charges, and point dipoles and quadrupoles, which can be equivalently represented by multiple point charges. The force fields can be exported as input files for the simulation programmes ms2 and ls1 mardyn, GROMACS, and LAMMPS. To characterise the semantics associated with the numerical database content, a force field nomenclature is introduced that can also be used in other contexts in materials modelling at the atomistic and mesoscopic levels. The models of the pure substances that are included in the database were generally optimised such as to yield good representations of experimental data of the vapour–liquid equilibrium with a focus on the vapour pressure and the saturated liquid density. In many cases, the models also yield good predictions of caloric, transport, and interfacial properties of the pure fluids. For all models, references to the original works in which they were developed are provided. The models can be used straightforwardly for predictions of properties of fluid mixtures using established combination rules. Input errors are a major source of errors in simulations. The MolMod database contributes to reducing such errors.

KEYWORDS:

• Molecular models
• force field database
• thermophysical properties
• molecular dynamics
• Monte Carlo

Acknowledgments

We gratefully appreciate running test simulations for the validation of the ls1 mardyn, GROMACS and LAMMPS input files by Matthias Heinen, Edder J. Garcia and Angelo Damone, respectively. The simulations for the parametrisation of the force fields were carried out on the HazelHen at High Performance Computing Center Stuttgart (HLRS) under the grant MMHBF2 as well as on the SuperMUC at Leibniz Supercomputing Centre (LRZ) Garching under the grant SPARLAMPE (pr48te). The present research was conducted under the auspices of the Boltzmann-Zuse Society of Computational Molecular Engineering (BZS).

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The authors gratefully acknowledge funding of the present work by the Reinhart Koselleck programme of the Deutsche Forschungsgemeinschaft (DFG), and the TaLPas project by the German Federal Ministry of Education and Research (Bundesministerium für Bildung und Forschung) (BMBF). The co-authors Simon Stephan and Hans Hasse acknowledge funding by the European Union's “Horizon 2020 research and innovation programme” (grant agreement No. 694807 – ENRICO) and the co-author Martin Horsch by (grant agreement No. 760907 – VIMMP).