Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe

O: Fachverband Oberflächenphysik

O 43: Oxides and Insulators: Adsorption I

O 43.6: Vortrag

Dienstag, 8. März 2016, 15:15–15:30, H6

An ab initio study of adsorption and defect formation energies at the surface of Ni-doped MgO – a catalyst for the Sabatier process — •Aliaksei Mazheika, Sergey Levchenko, and Matthias Scheffler — Fritz-Haber-Institut der MPG, Berlin, Deutschland

We present an ab initio study of Ni_Mg defects in Ni-doped MgO - a promising material for the catalytic conversion of methane and CO₂. First, a fraction of exact exchange α in the hybrid DFT functional HSE06 is identified such that HSE(α) closely reproduces CCSD(T) formation energies of Ni_Mg in MgO bulk, as well as the adsorption energies of CO and H₂ at the surface defects, calculated with embedded cluster models. HSE(α = 0.3) is found to reproduce all the CCSD(T) results with deviations of at most 0.1 eV. Using this functional and periodic models, we calculate the formation energy dependence on the position of Ni_Mg (in the bulk, subsurface, at the (001) terrace, monolayer step and corner), and the influence of the defects on the adsorption energies of CO₂, CH₄, CO, and H₂. The presence of Ni_Mg at the surface is found to have a minor effect on the adsorption energies of CH₄ and CO₂, independent of the coordination of the adsorption site, whereas it increases the adsorption energy of CO and particularly H₂. The adsorption energy of CO₂ calculated with HSE(α = 0.3) plus the ab initio many-body van der Waals correction [1] is about 0.4 eV larger than the PBE adsorption energy. - [1] A. Tkatchenko et al. PRL. 108, 236402 (2012)