  We study the scaling of logarithmic negativity between adjacent subsystems in
critical fermion chains with various inhomogeneous modulations through
numerically calculating its recently established lower and upper bounds. For
random couplings, as well as for a relevant aperiodic modulation of the
couplings, which induces an aperiodic singlet state, the bounds are found to
increase logarithmically with the subsystem size, and both prefactors agree
with the predicted values characterizing the corresponding asymptotic singlet
state. For the marginal Fibonacci modulation, the prefactors in front of the
logarithm are different for the lower and the upper bound, and vary smoothly
with the strength of the modulation. In the delocalized phase of the
quasi-periodic Harper model, the scaling of the bounds of the logarithmic
negativity as well as that of the entanglement entropy are compatible with the
logarithmic scaling of the homogeneous chain. At the localization transition,
the scaling of the above entanglement characteristics holds to be logarithmic,
but the prefactors are significantly reduced compared to those of the
translationally invariant case, roughly by the same factor.
