  We aim to understand how the van der Waals force between neutral adatoms and
a graphene layer is modified by uniaxial strain and electron correlation
effects. A detailed analysis is presented for three atoms (He, H, and Na) and
graphene strain ranging from weak to moderately strong. We show that the van
der Waals potential can be significantly enhanced by strain, and present
applications of our results to the problem of elastic scattering of atoms from
graphene. In particular we find that quantum reflection can be significantly
suppressed by strain, meaning that dissipative inelastic effects near the
surface become of increased importance. Furthermore we introduce a method to
independently estimate the Lennard-Jones parameters used in an effective model
of He interacting with graphene, and determine how they depend on strain. At
short distances, we find that strain tends to reduce the interaction strength
by pushing the location of the adsorption potential minima to higher distances
above the deformed graphene sheet. This opens up the exciting possibility of
mechanically engineering an adsorption potential, with implications for the
formation and observation of anisotropic low dimensional superfluid phases.
