Tight-binding electronic structure calculations for the TiFe(001) surface

We present a self-consistent tight-binding calculation of the electronic structure for the (001) surface of TiFe in the CsCl (B2) structure. The results were obtained using a three-center s-p-d orthogonal tight-binding Hamiltonian, within the surface Green function matching formalism. We have analyzed the local density of states (LDOS) for cases where Fe or Ti forms the surface layer. When Fe forms the atomic surface layer, our calculations show that the corresponding LDOS consists predominantly of bonding states, like in the bulk, but with a value at the EF enhanced by ∼160% with respect to the bulk. When Ti forms the atomic surface layer, the corresponding LDOS consists mainly of antibonding states, but with a value at EF raised compared with the bulk by ∼350%; a strong d-band narrowing was found in this case. Additionally, the trends to surface segregation and chemical activity for these surfaces are discussed.