Active-matter
systems feature discrete particles that can convert
stored or ambient free energy into motion. To realize the engineering
potential of active matter, there is a strong need for predictive
and theoretically grounded techniques for describing transport in
these systems. In this work, we perform molecular-dynamics (MD) simulations
of a model active-matter system, in which we vary the total fraction
of active particles (0.01 ≤ ϕ ≤ 0.5) as well as
the degree of activity of the active particles. These simulations
reveal a fascinating array of transport phenomena, including activity-enhanced
diffusion coefficients. By adapting an existing result for binary
(inactive) fluids, we demonstrate the existence of an excess entropy
scaling relation in an active system. This relationship is well supported
by our MD results and establishes a new connection between transport
(dynamics) and structure (statics) in active matter, a promising step
for predictive and generalizable models of other transport phenomena
in such systems.