0000000000089692
AUTHOR
Kersti Hermansson
A First-Principles Study of the Ag/a-Al2O3(0001) Interface
Ab initio simulations of the Ag/a-Al2O3(0001) interface have been performed for periodic slab models. We have considered Al- and O-terminated corundum surfaces, low and high substrate coverages by silver, as well as the two preferred Ag adsorption sites. The two different terminations give rise to qualitatively different results: silver physisorption on the Al-terminated substrate and chemisorption on O-terminated one. The latter could be treated as a possible model for the defective Al-terminated substrate, where the outermost aluminium ions are removed (completely or partly). This makes O-terminated surface highly reactive towards a deposited metal, in order to restore initial corundum st…
The adhesion properties of the Ag/α-Al2O3() interface: an ab initio study
Ab initio computer simulations of the atomic and electronic structure of the Ag/a-Al2O3(0 0 0 1) (corundum) interface have been performed for a periodic two-dimensional slab model using the Hartree–Fock method and a posteriori electron correlation corrections.We have considered both Al- and O-terminated corundum substrate surfaces.The dependence of the adhesion energy on the interfacial distance has been analyzed for the two most favorable Ag adsorption positions over corundum and for two different metal coverages (a 1/3 monolayer (ML) of the Ag(1 1 1) crystallographic plane and a full Ag(1 1 1) monolayer).The two different terminations (Al- and O-) give rise to qualitatively different resu…
First principles simulations of F centers in cubic SrTiO 3
Atomic and electronic structure of regular and O-deficient SrTiO3 have been studied. Several types of first principles atomistic simulations: Hartree-Fock method, Density Functional Theory, and hybrid HF-DFT functionals, have been applied to periodic models that consider supercells of different sizes (ranging between 40 and 240 atoms). We confirm the ionic character of the Sr-O bonds and the high covalency of the Ti-O2 substructure. For the stoichiometric cubic crystal; the lattice constant and bulk modulus correctly reproduce the experimental data whereas the band gap is only properly obtained by the B3PW functional. The relaxed geometry around the F center shows a large expansion of the t…
Ab initio simulations of silver film adhesion on α-Al2O3 (0 0 0 1) and MgO (1 0 0) surfaces
The atomic and electronic structure of the Ag/MgO (1 0 0) and Ag/alpha-Al2O3(0 0 0 1) interfaces are calculated by means of the ab initio Hartree-Fock approach combined with a supercell model. The electronic density distribution and the interface binding energy/equilibrium distance for both interfaces are analyzed. For a complete (1:1) surface coverage of the MgO surface the energetically most favorable adsorption position for the Ag atom is above the O atom. For the Ag/alpha-Al2O3 interface the preferable adsorption positions for the Ag atom are over centers of either large equilateral oxygen triangles (in Al-substituted sites of Al-terminated corundum surface) or isosceles oxygen triangle…