  The treatment of chemical mixing in the radiative envelopes of
intermediate-mass stars has hardly been calibrated so far. Recent asteroseismic
studies demonstrated that a constant diffusion coefficient in the radiative
envelope is not able to explain the periods of trapped gravity modes in the
oscillation spectra of $\gamma$ Doradus pulsators. We present a new generation
of MESA stellar models with two major improvements. First, we present a new
implementation for computing radiative accelerations and Rosseland mean
opacities that requires significantly less CPU time. Second, the inclusion of
shear mixing based on rotation profiles computed with the 2D stellar structure
code ESTER is considered. We show predictions for the mode periods of these
models covering stellar masses from 1.4 to 3.0${\rm M_\odot}$ across the main
sequence (MS), computed for different metallicities. The morphology of the
chemical mixing profile resulting from shear mixing in combination with atomic
diffusion and radiative levitation does allow for mode trapping, while the
diffusion coefficient in the outer envelope is large ($>10^{6}\,{\rm
cm^2\,s^{-1}}$). Furthermore, we make predictions for the evolution of surface
abundances for which radiative accelerations can be computed. We find that the
N/C and C/O abundance ratios correlate with stellar age. We predict that these
correlations are observable with precisions $\lesssim 0.1$ dex on these ratios,
given that a precise age estimate can be made.
