  Real-time time-dependent density functional theory (TDDFT) is widely
considered to be the most accurate available method for calculating electronic
stopping powers from first principles, but there have been relatively few
assessments of the consistency of its predictions across different
implementations. This problem is particularly acute in the warm dense regime,
where computational costs are high and experimental validation is rare and
resource intensive. We report a comprehensive cross-verification of stopping
power calculations in conditions relevant to inertial confinement fusion
conducted using four different TDDFT implementations. We find excellent
agreement among both the post-processed stopping powers and relevant
time-resolved quantities for alpha particles in warm dense hydrogen. We also
analyze sensitivities to a wide range of methodological details, including the
exchange-correlation model, pseudopotentials, initial conditions, observable
from which the stopping power is extracted, averaging procedures, projectile
trajectory, and finite-size effects. We show that among these details,
pseudopotentials, trajectory-dependence, and finite-size effects have the
strongest influence, and we discuss different strategies for controlling the
latter two considerations.
