  The MolMod database is presented, which is openly accessible at
http://molmod.boltzmann-zuse.de/ and contains presently intermolecular force
fields for over 150 pure fluids. 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
programs 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 data base 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.
