  We combine the \textit{ab initio} symmetry-adapted no-core shell model
(SA-NCSM) with the single-particle Green's function approach to construct
optical potentials rooted in first principles. Specifically, we show that total
cross sections and phase shifts for neutron elastic scattering from a $^4$He
target with projectile energies between 0.5 and 10 MeV closely reproduce the
experiment. In addition, we discuss an important new development that resolves
a long-standing issue with spurious center-of-mass motion in the Green's
function formalism for many-body approaches. The new development opens the path
for first-principle predictions of cross sections for elastic scattering of
single-nucleon projectiles, nucleon capture and deuteron breakup reactions,
feasible for a broad range of open-shell spherical and deformed nuclei in the
SA-NCSM approach.
