  We present simple models to describe the in-plane and the out-of-plane
lattice relaxation in twisted bilayer and symmetrically twisted trilayer
graphene. Analytical results and series expansions show that for twist angles
{\theta} > 1 $^{\circ}$, the in-plane atomic displacements lead to
pseudomagnetic fields weakly dependent on {\theta}. In symmetrically twisted
trilayer graphene, the central layer in-plane relaxation is greatly enhanced.
The joint effect of the relaxation-induced pseudoscalar potentials and the
associated energy difference between interlayer dimer and non-dimer pairs
resulted in a significant electron-hole asymmetry both in twisted bilayer and
trilayer graphene.
