Electrolytes

SSE-MD

Summary

Performance in predicting the structural dynamics of 49 solid-state electrolyte (SSE) systems via long-timescale molecular dynamics. Systems include Li, Cs, Cu, and Na-containing ionic conductors spanning a temperature range of 300–1300 K. Radial distribution functions (RDFs) computed from model trajectories are compared against ab initio molecular dynamics (AIMD) reference data.

Metrics

  1. RDF Score

Minimum RDF similarity score across all systems and element pairs.

For each system, a 1 ns NVT molecular dynamics trajectory is generated using a Nosé-Hoover chain thermostat at the target temperature. After discarding an equilibration period of 5 ps, pairwise radial distribution functions (RDFs) are computed for all unique element pair combinations. Each RDF is compared to the corresponding AIMD reference using the normalised mean absolute error metric described in Schran et al. (2021):

\[\epsilon = \frac{\sum |g_\mathrm{model}(r) - g_\mathrm{ref}(r)|}{\sum g_\mathrm{model}(r) + \sum g_\mathrm{ref}(r)}\]

The per-pair score is defined as \(1 - \epsilon\), and the per-system score is the minimum score across all element pairs. The reported RDF Score is the minimum across all systems. A score of 1.0 indicates perfect agreement with the reference data.

  • C. Schran, F. L. Thiemann, P. Rowe, E. A. Müller, O. Marsalek, A. Michaelides, “Machine learning potentials for complex aqueous systems made simple”, Proceedings of the National Academy of Sciences 118, e2110077118 (2021).

  1. Stable trajectories

Percentage of systems completed without exploding.

During each MD run the configuration is checked periodically for non-finite positions, energies or forces, which terminates the trajectory. A system counts as stable only if no such failure occurs and the full 1 ns of MD is completed. The reported value is the percentage of the 49 systems that are stable, so 100% indicates that every trajectory ran to completion.

Benchmark speed

Very slow: tests are likely to take hours to days to run on GPU.

Data availability

Input structures:

  • 49 solid-state electrolyte structures comprising Li, Cs, Cu, and Na-containing ionic conductors at temperatures between 300 K and 1300 K.

Reference data:

  • AIMD reference RDFs computed with VASP using the PBE functional from

  • López, C., Rurali, R. & Cazorla, C. How Concerted Are Ionic Hops in Inorganic Solid-State Electrolytes? J. Am. Chem. Soc. 146, 8269–8279 (2024).