  We present a generic theoretical model for the structuring of a relativistic
jet propagating through the ejecta of a binary neutron star merger event,
introducing the effects of the neutron conversion-diffusion, which provides a
baryon flux propagating transversely from the ejecta towards the jet axis. This
results naturally in an increased baryon load structure of the outer jet with
the approximate isotropic energy distribution $E_{iso}(\theta) \propto
\theta^{-4}$, which is compatible with the first gravitational wave and short
gamma-ray burst event GW170817/GRB 170817A observed at an off-axis angle of the
jet.
