Magnetic properties of point defects in iron within the tight-binding-bond Stoner model

The tight-binding Stoner model of band magnetism is generalized to account for local charge neutrality by working within the tight-binding-bond (TBB) representation of the binding energy. We show that the analytic forces within this TBB Stoner model take a very simple form because neither the renormalization in the on-site energies due to local charge neutrality nor the change in local magnetic moments due to atomic displacement enters explicitly. This d band TBB Stoner model is found to reproduce qualitatively the variations in local moments on and around point defects that are predicted by first principles density functional theory. In agreement with experiments, the formation energies show that the most stable self-interstitial defect is the < 110 > dumbbell.