Sensitivity Analysis for ReaxFF Reparametrization Using the Hilbert–Schmidt Independence Criterion

We
apply a global sensitivity method, the Hilbert–Schmidt
independence criterion (HSIC), to the reparametrization of a Zn/S/H
ReaxFF force field to identify the most appropriate parameters for
reparametrization. Parameter selection remains a challenge in this
context, as high-dimensional optimizations are prone to overfitting
and take a long time but selecting too few parameters leads to poor-quality
force fields. We show that the HSIC correctly and quickly identifies
the most sensitive parameters and that optimizations done using a
small number of sensitive parameters outperform those done using a
higher-dimensional reasonable-user parameter selection. Optimizations
using only sensitive parameters (1) converge faster, (2) have loss
values comparable to those found with the naive selection, (3) have
similar accuracy in validation tests, and (4) do not suffer from problems
of overfitting. We demonstrate that an HSIC global sensitivity is
a cheap optimization preprocessing step that has both qualitative
and quantitative benefits which can substantially simplify and speed
up ReaxFF reparametrizations.