Stability and electronic structure of MgAl2O4(1 1 1) surfaces: A first-principles study

• The interplanar displacements for eight terminations of MgAl2O4(1 1 1) show a typical damped oscillation during the relaxation process.
• The PDOSs and atomic populations of MgAl2O4(1 1 1) surfaces are similar to those of MgO(1 1 1) or Al2O3(0 0 1).

The surface relaxation, cleavage energies and surface energies, surface grand potential and surface electronic structure of eight different terminations of MgAl2O4(1 1 1) surfaces have been calculated with the first principles methods based on the density functional theory. Results of the relaxed structure for each termination show that the layer distances near the surface oscillate in a damping style with a conserved profile. By comparing the surface energies of the eight terminations, Mg(O)- and Al(Mg)-terminations have relatively small surface energies. Taking into account the influence of the chemical environment as a function of the relative richness in O and Al, Mg(Al)-, Al(Mg)-, O(Al)- and O2(Al)-terminations are more stable, in particular, Mg(Al)-termination is the most stable in O- and Al-rich environments, and O2(Al)-termination is the most stable in O- and Al-poor conditions. According to the calculated electronic properties, the four terminations are metallic, and their Fermi levels move up. Due to the special crystal structure of MgAl2O4, its (1 1 1) surfaces exhibit some properties similar to those of Al2O3(0 0 1) and MgO(1 1 1) surfaces.

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