  Molecular dynamics (MD) simulations involving reactive potentials can be used
to model material failure. The empirical potentials which are used in such
simulations are able to adapt to the atomic environment, at the expense of a
significantly higher computational cost than non-reactive potentials. However,
during a simulation of failure, the reactive ability is needed only in some
limited parts of the system, where bonds break or form and the atomic
environment changes. Therefore, simpler non-reactive potentials can be used in
the remainder of the system, provided that such potentials reproduce correctly
the behavior of the reactive potentials in this region, and that seamless
coupling is ensured at the interface between the reactive and non-reactive
regions. In this article, we propose a methodology to combine a reactive
potential with a non-reactive approximation thereof, made of a set of harmonic
pair and angle interactions and whose parameters are adjusted to predict the
same energy, geometry and Hessian in the ground state of the potential. We
present a methodology to construct the non-reactive approximation of the
reactive potential, and a way to couple these two potentials. We also propose a
criterion for on-the-fly substitution of the reactive potential by its
non-reactive approximation during a simulation. We illustrate the correctness
of this hybrid technique for the case of MD simulation of failure in
two-dimensional graphene originally modeled with REBO potential.
