Impact of Strong Correlation Effect on Adsorption Structure and Magnetic Moments

The first-principles calculations are performed based on the density functional theory (DFT) [1] with generalized gradient approximation (GGA) in the form of Perdew-BurkeErnzerhof (PBE) functional [2] as implemented in Vienna Abinitio Simulation Package (VASP) [3]. The GGA +U method which treats the on-site repulsion interactions of 3d electrons in a mean field manner is used to evaluate the strong correlation effect in TM, and a typical value of U = 4 eV and J = 0.9 eV are used for all TM concerned [4]. The lattice constant a = 3.86 Å of silicene and the buckling distance δ = 0.44 Å are obtained corresponding to the global minima on the BornOppenheimer surface, which agree with existing theoretical data [5, 6]. As to the structure relaxation, all atoms are allowed to relax freely along all directions and all parameters are chosen to converge the forces to less than 0.01 eV/Å. A vacuum space of 20 Å is set to prevent the interaction between silicene and its periodic images along c-axis. Convergence tests with respect to energy cutoff and k points sampling are performed to ensure numerical accuracy of total energy. We find an energy cutoff of 420 eV and Γ centered MonkhorstPack grids of 8 × 8 × 1 for k point sampling are enough to converge the difference in total energy to around 1meV.