  As nanofabrication techniques become more precise, with ever smaller feature
sizes, the ability to model nonlocal effects in plasmonics becomes increasingly
important. While nonlocal models based on hydrodynamics have been implemented
using various computational electromagnetics techniques, the finite-difference
time-domain (FDTD) version has remained elusive. Here we present a
comprehensive FDTD implementation of nonlocal hydrodynamics, including for
parallel computing. As a sub-nanometer step size is required to resolve
nonlocal effects, a parallel implementation makes the computational cost of
nonlocal FDTD more affordable. We first validate our algorithms for small
spherical metallic particles, and find that nonlocality smears out staircasing
artifacts at metal surfaces, increasing the accuracy over local models. We find
this also for a larger nanostructure with sharp extrusions. The large size of
this simulation, where nonlocal effects are clearly present, highlights the
importance and impact of a parallel implementation in FDTD.
