(342t) Si and C Models as the Basis for Regression-Driven Development of the Interface Force Field

The Interface Force Field (IFF) project centers around the construction of an all-atom force field and surface model database for simulation of nanostructures of 1 to 1000 nm size, including minerals, metals, oxides, and (bio)polymers.¹ To achieve this aim, the IFF project develops model systems that mimic experimentally observed behavior, which is validated through benchmarks such as density, surface energy, and melting point.

Via an ancillary electron method, we constructed a silicon (Si) model which reproduces a density of 2.312 g/cm³ at 298 K, compared to 2.329 g/cm³ as experimentally measured.² Our model is representative of experimentally observed Si melting temperature near 1687 K, largely owing to accurate description of surface energy which we demonstrate through the calculation of the Si(111) surface energy within 5% error of experimental estimates.³ A similar model was constructed for carbon. Si and C were assembled to simulate the SiC layer that results from heterogeneous nucleation between C and molten Si during melt infiltration experiments. In the solid-state diffusion-controlled regime of the reaction occurring at the interface, the diffusivity of C through the initial nucleation layer of SiC governs further layer growth. We calculated the diffusivity of C through SiC layers of various thickness in order to investigate the effect of the time-dependent permeability on layer growth.

Where diffusivity is critical to reaction rate, as in the SiC system, a model that captures nanoscale system dynamics is necessary for micron-scale material simulation. Through accurate description of diffusivity in SiC, our Si and C ancillary electron models advance the capabilities of Interface Force Field for ceramic materials.

References:

(1) Heinz, H., Lin, T.-J., Kishore Mishra, R., & Emami, F. S. (2013). Thermodynamically Consistent Force Fields for the Assembly of Inorganic, Organic, and Biological Nanostructures: The INTERFACE Force Field. Langmuir, 29(6), 1754–1765. https://doi.org/10.1021/la3038846

(2) Assael, M. J., Armyra, I. J., Brillo, J., Stankus, S. V., Wu, J., & Wakeham, W. A. (2012). Reference Data for the Density and Viscosity of Liquid Cadmium, Cobalt, Gallium, Indium, Mercury, Silicon, Thallium, and Zinc. Journal of Physical and Chemical Reference Data, 41(3), 033101. https://doi.org/10.1063/1.4729873

(3) Tyson, W. R., & Miller, W. A. (1977). Surface free energies of solid metals: Estimation from liquid surface tension measurements. Surface Science, 62(1), 267–276. https://doi.org/10.1016/0039-6028(77)90442-3