(750c) Achieving Large Scale Quantum-Accurate Reactive Molecular Dynamics: The Chebyshev Interaction Model for Efficient Simulations (ChIMES)

Many of the most challenging problems in chemical engineering involve reactivity in complicated systems. First principles methods like density functional theory (DFT) and density functional tight binding (DFTB) are attractive for studying these problems, however, both methods are confined to systems of a few 100s atoms, and in the case of DFT, 10s of ps. These limitations have motivated extensive work towards development of accurate, scalable, and reliable reactive force fields but these models generally rely on complicated functional forms requiring time consuming parameterization schemes. As a result, the physiochemical space over which parameters are available is limited.

In this work, we present the Chebyshev Interaction Model for Efficient Simulations (ChIMES), a new reactive force field and semi-automated fitting framework that retains most of the accuracy of DFT while decreasing computational requirements by several orders of magnitude. ChIMES models are comprised of n-body atomic interactions constructed from linear combinations of Chebyshev polynomials, and are entirely linear in fitting coefficients. Thus, model parameters can be rapidly (and iteratively) generated by force matching to short DFT trajectories. ChIMES models are particularly well suited for studies that frequently rely on costly quantum simulations for elucidation and interpretation of experiments, and to date, have been successfully applied to problems including chemical reactivity under extreme conditions and surface catalysis, which can probe time and lengths that are many orders of magnitude longer that what can be achieved with standard DFT. ChIMES is able to overcome this time and length scale gap, allowing for direct, one to one comparisons to experiment, in many cases for, the first time. Model details will be presented as will application to reactive nucleation of a carbon phase from liquid carbon monoxide.

This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. Document release number LLNL-ABS-749589