Gabriel Canto

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

Abstract 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.

ELECTRONIC LOCAL DENSITY OF STATES FOR THE TiNi(001) SURFACE

We present a self-consistent tight-binding calculation of the electronic structure for the (001) surface of TiNi in the CsCl (B2) structure. The results were obtained using a three-center s–p–d orthogonal tight-binding Hamiltonian fitted to first-principles calculations, within the surface Green function matching formalism. We have analyzed the local density of states (LDOS) for cases with Ni or Ti at the surface layer. For the case where Ni is at the atomic surface layer we find that the corresponding LDOS consists predominantly of bonding states, like in the bulk but with a value at EF reduced by 38% with respect to the bulk; for this surface a strong peak in the LDOS was found at -1.4 eV below EF. For the case where Ti is at the atomic surface layer the corresponding LDOS consists mainly of antibonding states, but with a value at EF higher than in the bulk by 30%. Comparatively, the case where Ni is at the surface layer presents lower values of LDOS at EF and d holes with respect to the case where Ti is at the surface layer, and therefore more chemical activity can be expected for the Ti surface.

Electronic structure of FCC carbon

We report first-principles calculations of the electronic structure for carbon in the fcc structure with the experimentally observed lattice parameter. The calculated orbital population shows that the chemical bond in fcc carbon is close to the s2p2 bonding with a small s-p hybridization. We find that, in contrast to graphite and diamond, fcc carbon exhibits metallic behavior with an electronic density of states at the Fermi level of 0.5 states/(eV atom).