We report on a detailed first-principles local-density-functional investigation of the structural, electronic and dynamical properties of a MgB2 free surface in both unreconstructed ideal terminations and in the case of Na coverage. Our study shows that in the case of a B-terminated surface the density of states at the Fermi level is significantly larger than in the bulk, a behavior that might lead to an enhancement of superconducting properties. We find the Mg-terminated surface to be the most stable structure in the whole range admitted by the chemical potentials, in agreement with very recent experimental results. The Na-covered surface is just slightly less stable than the Mg-terminated one in B-rich conditions and cannot be ruled out as a potentially relevant metastable structure. We rationalize the thermodynamical trends and the dynamical properties of the surfaces considered in terms of the B-σ state filling; in particular, we find that the larger the filling the more stable the surface and the higher the frequency of the vibrational modes localized at the crystal surface.

Electronic and dynamical properties of the MgB2 surface: Implications for the superconducting properties

Profeta, G.;Continenza, A.;Bernardini, Fabio;
2002-01-01

Abstract

We report on a detailed first-principles local-density-functional investigation of the structural, electronic and dynamical properties of a MgB2 free surface in both unreconstructed ideal terminations and in the case of Na coverage. Our study shows that in the case of a B-terminated surface the density of states at the Fermi level is significantly larger than in the bulk, a behavior that might lead to an enhancement of superconducting properties. We find the Mg-terminated surface to be the most stable structure in the whole range admitted by the chemical potentials, in agreement with very recent experimental results. The Na-covered surface is just slightly less stable than the Mg-terminated one in B-rich conditions and cannot be ruled out as a potentially relevant metastable structure. We rationalize the thermodynamical trends and the dynamical properties of the surfaces considered in terms of the B-σ state filling; in particular, we find that the larger the filling the more stable the surface and the higher the frequency of the vibrational modes localized at the crystal surface.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11697/121883
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