Self-organization of ultra-thin uranium film

We have studied the adsorption behaviors of uranium (U) atoms coated graphene at different coverage ratios using first-principles calculations. Isolated U atom is demonstrated to be more likely to stay on the hollow site of graphene with a large adsorption energy of 2.80 eV and high magnetic moment of 5.07 μ_B. It seems that two U atoms tend to adsorb on the nearest neighbor hollow sites of graphene. As the concentration of U atom increases, no U-dimer or U-cluster appears with increasing coverage ratio. In the case of coverage ratio of 2/3, U atoms on graphene is the most stable configuration, where each U atoms are uniformly-distributed in U network with honeycomb lattice. The adsorption energy is as large as 2.57 eV per U atom. Moreover, the spin–orbit coupling effect on electronic band structures is outstanding, which induces the degeneracy bands splitting. Our calculations will provide profound background to understand the adsorption behaviors of U atoms on graphene.