Comparison of the experimentally determined diffraction prob- abilities (symbols) with diffraction probabilities computed with the PBEα- vdW-DF2 XC functional for (a) specular scattering (black) and (b) several first order out-of-plane (blue and red) and in-plane (green and pink) dif- fractive transitions for incidence along the <1,1, ̄2> incidence direction for n-H2 (20 j=0, 75 j=1 ,5 j=2)fromPt(111)withanini- tial parallel energy of 55 meV. The probabilities for symmetry equivalent transitions are summed.