All-electron and pseudopotential study of the spin-polarization of the V(001) surface: LDA versus GGA

The spin-polarization at the V(001) surface has been studied by using different local [local spin-density approximation (LSDA)] and semilocal [generalized gradient approximation (GGA]) approximations to the exchange-correlation potential of DFT within two ab initio methods: the all-electron tight-binding linear muffin-tin orbital atomic-sphere approximation and the pseudopotential linear combination of atomic orbitals code SIESTA (Spanish initiative for electronic simulations with thousands of atoms). A comparative analysis is performed first for the bulk and then for a N-layer V(001) film (7<=N<=15). The LSDA approximation leads to a nonmagnetic V(001) surface with both theoretical models in agreement (disagreement) with magneto-optical Kerr (electron-capture spectroscopy) experiments. The GGA within the pseudopotential method needs thicker slabs than the LSDA to yield zero moment at the central layer, giving a high surface magnetization (1.70 Bohr magnetons), in contrast with the nonmagnetic solution obtained by means of the all-electron code.