Molecular dynamics

Liquid densities

Summary

Performance in predicting densities for 61 organic liquids, each system consisting of about 1000 atoms. The dataset covers aliphatic, aromatic molecules, as well as different functional groups and halogenated molecules.

Metrics

  1. Density error

For each system, the density is calculated by taking the average density of an NPT molecular dynamics run. The initial part of the simulation, here 500 ps, is omitted from the density calculation. This is compared to the reference density, obtained from experiment.

Computational cost

Very high: tests are likely to take several days to run on GPU.

Data availability

Input structures:

  • Weber et al., Efficient Long-Range Machine Learning Force Fields for

    Liquid and Materials Properties. arXiv:2505.06462 [physics.chem-ph]

Reference data:

  • Same as input data

  • Experimental

Water density

Summary

Performance in predicting the density of water at temperatures of 270, 290, 300, and 330 K. The water systems consist of 333 molecules.

Metrics

  1. Density error

For each system, the density is calculated by taking the average density of an NPT molecular dynamics run. The initial part of the simulation, here 500 ps, is omitted from the density calculation. This is compared to the reference density, obtained from experiment.

Computational cost

Very high: tests are likely to take several days to run on GPU.

Data availability

Input structures:

  • Weber et al., Efficient Long-Range Machine Learning Force Fields for Liquid and Materials Properties. arXiv:2505.06462 [physics.chem-ph]

Reference data:

  • Same as input data

  • Experimental

Water ethanol density curves

Summary

Benchmark of the density of water-ethanol mixtures for different concentrations of ethanol, compare to experiment. 1 ns of NPT MD on about 120 water/ethanol molecules for 6 concentrations.

Metrics

  1. rms of the density difference.

  2. rms of the excess volume difference.

  3. Concentration of the minimal excess volume.

For each system, the density is calculated by taking the average density of an NPT molecular dynamics run. The initial part of the simulation, here 500 ps, is omitted from the density calculation. This is compared to the reference density, obtained from experiment. The excess volume is computed as the difference between the actual molar volume of the mixture and the ideal molar volume obtained by linear combination of the pure-component molar volumes. The concentration of the minimal excess volume is estimated by fitting a quadratic to the three grid points surrounding the minimum and taking the vertex of the parabola.

Computational cost

Very high: tests are likely to take several days to run on GPU.

Data availability

Input structures: Packmol generated

Reference data: * M. Southard and D. Green, Perry’s Chemical Engineers’ Handbook, 9th Edition. McGraw-Hill Education, 2018. * Experimental