Spin polarized DFT calculations were performed using the Vienna ab initio simulation package (VASP). The electron-ion interaction was described by the projector-augmented-wave (PAW) method 101 and for the exchange-correlation interaction we used Perdew-Burke-Ernzerhof (PBE) version 102,103 of the generalized gradient approximation (GGA). The Grimme's DFT + D3 method 104 was used to account for van der Waals (vdW) interactions. The kinetic energy cutoff was set at 450 eV and a convergence criterion of 10 -6 eV and 10 -5 eV was employed for the electronic energy and the geometry relaxation, respectively. The Brillouin zone was integrated using a 1 × 1 × 1 Monkhorst-Pack mesh centered at the Γ point. ) termination. All lattice parameters were optimized. For all cases the support was modeled using a single layer, buffered with a vacuum region of 20 Å to prevent artificial interactions between periodic images in the z direction. All atoms were allowed to relax during geometry optimization. In the SmSI support, the 4f electrons of Sm were treated as part of the core and hence no effective coulomb (Ueff) parameter was required.