reaxFF Reactive Force Field for Disulfide Mechanochemistry, Fitted to Multireference ab Initio Data

Mechanochemistry,
in particular in the form of single-molecule
atomic force microscopy experiments, is difficult to model theoretically,
for two reasons: Covalent bond breaking is not captured accurately
by single-determinant, single-reference quantum chemistry methods,
and experimental times of milliseconds or longer are hard to simulate
with any approach. Reactive force fields have the potential to alleviate
both problems, as demonstrated in this work: Using nondeterministic
global parameter optimization by evolutionary algorithms, we have
fitted a reaxFF force field to high-level multireference
ab initio data for disulfides. The resulting force field can be used
to reliably model large, multifunctional mechanochemistry units with
disulfide bonds as designed breaking points. Explorative calculations
show that a significant part of the time scale gap between AFM experiments
and dynamical simulations can be bridged with this approach.