Electronic structure of the surface of LaNi5 crystal

Abstract

The spin-polarized, all-electron, full-potential ab initio calculations have been performed for the electronic structure of the surface of LaNi5 crystal using the self-consistent cluster-embedding (SCCE) calculation method. The geometrical surface structure of LaNi5 crystal and its electronic structure having lowest ground-state energy are obtained, with the full relaxation of atomic positions along the direction perpendicular to the surface. On the surface of LaNi5 crystal, it is found that the La atom protruded out, and the Ni atoms caved in, so the surface becomes uneven which increases the contacting area with the hydrogen. The effective volume of the surface layer rises by 9%, which is in favour of the absorption of hydrogen. The Fermi level of the surface of LaNi5 crystal, which is made mainly of the 3d electrons of Ni,is much higher than that of body LaNi5. The valence band is not fully filled, which shows the metallic property. For the first two layers of the surface of LaNi5 crystal, there are 1.15 electrons transferred from La to Ni, and the two layers have small opposite spin magnetic moments which shows the paramagnetism. The density of state (DOS) of the valence band is obtained. The ionization potential and the electron affinity are calculated by the transition-state mathod. All calculated results show that although the properties of the surface of LaNi5 crystal are significantly different from that of body LaNi5, they are very similar to that of hydride LaNi5H7, so the structure of the surface of LaNi5 crystal is in favour of the absorption of hydrogen.