▎ 摘　　要

We report diffusion Monte Carlo calculations on the phase diagrams of para-H-2 and ortho-D-2 adsorbed on top of a first layer of the same substances on graphene. We found that the ground state of the second layer is a triangular incommensurate solid for both isotopes. The densities for promotion to a second layer and for the onset of a two-dimensional solid on that second layer compare favorably with available experimental data in both cases. DOI: 10.1103/PhysRevB.87.165403