An Efficient Reactive Force Field without Explicit Coordination Dependence for Studying Caustic Aluminum Chemistry

Reactive force fields (RFFs) are an expedient approach
to sample
chemical reaction paths in complex systems, relative to density functional
theory. However, there is continued need to improve efficiencies,
specifically in systems that have slow transverse degrees of freedom,
as in highly viscous and superconcentrated solutions. Here, we present
an RFF that is differentiated from current models (e.g., ReaxFF) by
omitting explicit dependence on the atom coordination and employing
a small parameter set based on Lennard-Jones, Gaussian, and Stillinger–Weber
potentials. The model was parametrized from AIMD simulation data and
is used to model aluminate reactivity in sodium hydroxide solutions
with extensive validation against experimental radial distribution
functions, computed free energy profiles for oligomerization, and
formation energies. The model enables simulation of early stage Al(OH)3 nucleation which has significant relevance to industrial
processing of aluminum and has a computational cost
that is reduced by 1 order of magnitude relative
to ReaxFF.