Molecular Crystals

X23

Summary

Performance in predicting lattice energies for 23 molecular crystals.

Metrics

  1. Lattice energy error

Accuracy of lattice energy predictions.

For each molecular crystal, lattice energy is calculated by taking the difference between the energy of the solid molecular crystal divided by the number of molecules it comprises, and the energy of the isolated molecule. This is compared to the reference lattice energy.

Computational cost

Low: tests are likely to take less than a minute to run on CPU.

Data availability

Input structures:

  • A. M. Reilly and A. Tkatchenko, Understanding the role of vibrations, exact exchange, and many-body van der waals interactions in the cohesive properties of molecular crystals, The Journal of chemical physics 139 (2013).

Reference data:

  • Same as input data

  • DMC

DMC-ICE13

Summary

Performance in predicting formation energies of common ice phases.

Metrics

  1. Ice phase mean absolute error

Accuracy of formation energy predictions.

For each ice polymorph, the formation energy is calculated by taking the difference between the energy of the polymorph divided by the number of molecules it comprises, and the energy of the isolated water molecule. This is compared to the reference formation energy.

Computational cost

Low: tests are likely to take less than a minute to run on CPU.

Data availability

Input structures:

  • F. Della Pia, A. Zen, D. Alfè, and A. Michaelides, Dmc-ice13: Ambient and high pressure polymorphs of ice from diffusion monte carlo and density functional theory, The Journal of Chemical Physics 157 (2022).

Reference data:

  • Same as input data

  • PBE-D3(BJ)

CPOSS209

Summary

Performance in predicting lattice energies of 209 organic molecular crystals from the CPOSS209 dataset.

Metrics

  1. Absolute lattice energy MAE

Accuracy of the absolute lattice energy predictions.

For each molecular crystal, lattice energy is calculated by taking the difference between the energy of the solid molecular crystal divided by the number of molecules it comprises, and the energy of the isolated molecule. This is compared to the reference lattice energy.

  1. Relative lattice energy MAE

Accuracy of the reltive lattice energy predictions.

We compute the lattice energies in the same way as before, but this time we compute the relative error. The relative error is computed by identifying the most stable polymorphs and, for each crystal, subtracting the lattice energy of the most stable polymorph. This metric cares more about the ranking of the crystal polymorphs rather than reproducing the reference values of the lattice energies.

Computational cost

Low: tests should take a few minutes on a CPU

Data availability

Input structures:

  • Structures are optimized at the PBE+TS level.

  • Louise S. Price, Matteo Paloni, Matteo Salvalaglio, and Sarah L. Price Crystal Growth & Design 2025 25 (9), 3186-3209 DOI: 10.1021/acs.cgd.5c00255

Reference data:

  • Same as input data

  • wb97md3 with 1b CCSD(T) corrections