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HL: Fachverband Halbleiterphysik

HL 80: Challenges in semiconductor theory

HL 80.4: Vortrag

Donnerstag, 19. März 2015, 15:45–16:00, EW 015

Electronic structure and adsorption properties of Ni substitutional defects at MgO(001). — •Aliaksei Mazheika, Sergey V. Levchenko, and Matthias Scheffler — Fritz-Haber-Institut der MPG, Berlin, DE

Ni-MgO solid solutions were demonstrated to be stable and active catalysts for CO₂ activation and conversion. However, despite numerous experimental investigations, the nature of the active sites, in particular at realistic conditions, remains unknown. As a first step towards understanding the nature of the sites, we calculate the electronic and atomic structure of Ni substitutional defects at the (100) surface of MgO, using the density-functional theory with the Heyd-Scuseria-Ernzerhof family of hybrid functionals HSE(α,ω) [1]. We determine the optimal fraction of the exact exchange α by comparing the positions of the defect levels and the valence-band maximum with respect to the vacuum level obtained with DFT and G₀W₀ where self-energy is evaluated with partial self-consistency of the eigenvalues. The obtained optimal value of α = 0.6 also gives an agreement within 0.1 eV between the DFT and MP2 energies of CO adsorption at the Ni defect. The MP2 adsorption energy calculated for a small embedded cluster model was previously shown to be very close to the CCSD(T) adsorption energy [2]. An optimal compromise (within 0.05 eV) can be achieved between the accuracy of the defect level alignment and the CO adsorption energy for α = 0.5.—[1] A.V. Krukau, O.A. Vydrov, A.F. Izmaylov, G. Scuseria. J. Chem. Phys., 125, 224106 (2006); [2] I. Mehdaoui, T. Klüner. J. Phys. Chem. A, 111, 13233 (2007).