### Description

Molecular simulations, in particular Monte Carlo Molecular Simulation and Molecular Dynamics Simulation, are methods for computing the properties of some kind of system, for which the intermolecular interactions are specified, via mathematical relationships derived from statistical mechanics. Since statistical mechanics itself makes no reference to molecular simulation of any kind, the properties that derive from statistical mechanics should not depend on the particular simulation algorithm used to compute properties for a specified model. Consequently, the results obtained from a molecular simulation can be thought of as characteristic of the model system, subject only to statistical uncertainty in those results, if the simulation technique follows necessary rules (e.g., detailed balance or microscopic reversibility, depending on the particular algorithm) and is computationally robust. Our goal in this project is to publish well-documented simulation results for reliable and well-vetted simulation software for a variety of systems, many of which are commonly used in molecular simulations, that can be treated similar to "standard reference data" that is generated in an laboratory setting. The data contained here may be used to validate and test new or existing molecular simulation software, as reference data, or for other appropriate applications. Most of the results contained here are generated in-house at NIST, but we will also include results from collaborators provided certain criteria are satisfied (see "Criteria..." below). In addition, it is our goal to provide data from molecular simulations in a raw or unprocessed format, when possible, so that the data may be reprocessed according to end users' particular needs. To that end, we also provide some software that may be used to reprocess data contained here.

**Benchmark Simulation Results for:**

- Lennard-Jones Fluid
- Stockmayer Fluid
- TraPPE Ethane
- TraPPE-UA n-Octane
- TraPPE-UA n-Butane
- SPC/E Water
- TIP3P Water
- TIP4P Water
- TIP4P/2005 Water
- Hard-Sphere Fluid
- Square-well Fluid
- TraPPE Carbon Dioxide
- TraPPE Nitrogen

**Simulation Reference Calculations:**

- Energy and Force (Virial) Reference Calculations: Fluid of Lennard-Jones atoms
- Energy Reference Calculations using the Ewald Summation Method: Fluid of SPC/E Water molecules - 10Å real-space cutoff
- Energy Reference Calculations using the Ewald Summation Method: Fluid of SPC/E Water molecules - 9Å real-space cutoff

**Criteria for Inclusion of Simulation Reference Data:**

Thermophysical properties of fluids that are entered into this database must conform to the following criteria:

*Reproducibility:*Thermophysical properties reported in this database must also include "metadata" that describes the simulation technique(s) and all simulation parameters used to obtain those properties. Simulation metadata must be sufficiently comprehensive such that an outside researcher could reproduce the properties given here (within the reported statistical uncertainty).*Accessible Force Fields:*Intermolecular potential models used to generate properties in this database must be available in the scientific literature or fully described in the simulation metadata.*Statistical Uncertainty:*All properties reported in this database must also include an estimate of the statistical uncertainty in each particular measurement. The statistical uncertainty must be computed using an appropriate technique that is described in the database.*Proprietary Software Prohibition:*In cases where prepackaged simulation software (e.g., LAMMPS, GROMACS, Towhee, etc.) has been used to generate properties in this database, such simulation software must be open-source and freely available to the scientific community.