The DFT calculations were performed using the Vienna Ab Initio Simulation Package (VASP) version 5.4.4, which uses the Projector Augmented Wave (PAW) method for modelling core and valence electrons. The Perdew-Burke-Enzerhof (PBE) exchange correlational functional of the Generalized Gradient Approximation (GGA) was chosen. For the long-range, non-local interactions that give rise to the van der Waals force, the D-3 method correction proposed by Grimme was used to describe the van der Waals interaction where indicated in this work. All of the VASP input files were automatically generated using pymatgen "io.vasp.sets" module, 41 however the magnetic moment of atoms and the spin polarization effect were not considered to allow for convergence of structural relaxation of slab calculations containing surface terminations.