Berlin 2018 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 62: Methods in Computational Materials Modelling (methodological aspects, numerics)

MM 62.1: Talk

Thursday, March 15, 2018, 15:45–16:00, TC 006

Uncertainty Quantification for Classical Effective Potentials — •Sarah Longbottom and Peter Brommer — University of Warwick, Coventry, UK

Effective potentials are an essential ingredient of classical molecular dynamics simulations. Little is understood of the errors incurred in representing the complex energy landscape of an atomic configuration by an effective potential containing considerably fewer parameters. The probabilistic sloppy model method [1] has been implemented in the potfit force matching code [2]. This introduces uncertainty quantification into the interatomic potential generation process. Uncertainties in the effective potential are propagated through MD to obtain uncertainties in quantities of interest, which are a measure of the confidence in the model predictions.

We demonstrate the technique using three potentials for nickel: two simple pair potentials, Lennard-Jones and Morse, and a local density dependant EAM potential. A sloppy model fit to DFT reference data is constructed for each potential to calculate the uncertainties in lattice constants, elastic constants and thermal expansion. These can be used to show the unsuitability of pair potentials for nickel. In contrast, with EAM we observe a decreased uncertainty in the model predictions. This shows that our method can capture the effects of the error incurred in the potential generation process without resorting to comparison with experiment or DFT.

[1] S. L. Frederiksen, et al., Phys. Rev. Lett., 93 (16), 2004.

[2] P. Brommer, et al., Modell. Simul. Mater. Sci. Eng., 23 (7), 2015.