Breakdown of the pseudopotential approximation for magnetic systems: Predicting magnetic quenching at the V(001) surface with spin-dependent pseudopotentials

Both experimentally [R.L. Fink et al., Phys. Rev. B 41, 10 175 (1990)] and using all-electron density-functional theory (DFT) methods, the V(001) surface exhibits little or no magnetization. Very recently, independent pseudopotential DFT calculations demonstrated the breakdown of the pseudopotential approximation, showing large magnetic moments at the surface of a V(001) slab. Here we demonstrate that use of spin-dependent pseudopotentials systematically corrects the inaccuracies of conventional spin-neutral pseudopotentials, producing results consistent with all-electron ones. We also show how the use of the spin-dependent pseudopotentials allows one to achieve a high level of accuracy without the numerical difficulties and cost associated with accurate spin-neutral pseudopotentials.