  Molecular dynamics simulations provide a versatile framework to study
interfacial heat transport, but their accuracy remains limited by the accuracy
of available interatomic potentials. In the past, researchers have adopted the
use of analytic potentials and simple mixing rules to model interfacial
systems, with minimal justification for their use. On the other hand,
contemporary machine learned interatomic potentials have greater complexity,
but have not seen rigorous validation of interfacial heat transport properties.
Moreover, when fitting to ab initio data, it is not known whether interface
systems small enough to be tractable for density functional theory calculations
can produce reasonable interatomic force constants. These and related questions
are studied herein using a model Ge/GaAs system, with a particular focus on the
harmonic force constants (IFC2s) of the interface. The ab initio IFC2s are
shown to recover near bulk-like values ~ 1-2 nm away from the interface, while
also exhibiting a complex relationship across the interface that likely
precludes any successful application of mixing rules. Two different spectral
neighborhood analysis potentials (SNAP) are developed to model the interface.
One is fit to the total forces, while the other is only used to describe the
anharmonicity, with a Taylor expansion used to describe the harmonic portion of
the potential. Each potential, along with their merits and issues are compared
and discussed, which provides important insights for future work.
