  Coarse-grained (CG) conformational surface hopping (SH) adapts the concept of
multisurface dynamics, initially developed to describe electronic transitions
in chemical reactions, to accurately describe classical molecular dynamics at a
reduced level. The SH scheme couples distinct conformational basins (states),
each described by its own force field (surface), resulting in a significant
improvement of the approximation to the many-body potential of mean force
[Phys. Rev. Lett. 121, 256002 (2018)]. The present study first describes CG SH
in more detail, through both a toy model and a three-bead model of hexane. We
further extend the methodology to non-bonded interactions and report its impact
on liquid properties. Finally, we investigate the transferability of the
surfaces to distinct systems and thermodynamic state points, through a simple
tuning of the state probabilities. In particular, applications to variations in
temperature and chemical composition show good agreement with reference
atomistic calculations, introducing a promising "weak-transferability regime,"
where CG force fields can be shared across thermodynamic and chemical
neighborhoods.
