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O: Fachverband Oberflächenphysik

O 74: Metal Substrates: Adsorption of O and/or H

O 74.8: Vortrag

Donnerstag, 28. Februar 2008, 16:45–17:00, MA 141

Strain effects in the adsorption on early transition metals — •Sebastian Schnur and Axel Groß — Institut für Theoretische Chemie, Universität Ulm, Germany

Strain effects in the adsorption on transition metal surfaces have recently attracted a lot of attention. Strain can significantly change the electronic structure and thus the reactivity and catalytic properties of these metals. These effects occur, e.g., if a metal grows pseudomorphically on another metals. In this context, only late transition metals have been investigated so far [1] because they are the common catalytically active metals. However, early transition metals such as titanium or manganese represent promissing candidate materials in light intermetallic compounds for hydrogen storage.

Compressive strain leads to a reduced overlap of the wave functions and thus to a narrowing of the d-band. Charge conservation leads either to a downshift of the d-band in early transition metals or to an upshift in late transition metals because of the different degree of filling. According to the d-band model, a downshift of the d-band should cause weaker interactions with adsorbates [1]. We performed density functional theory calculations to study for the first time strain effects in several early transition metals using hydrogen and CO adsorption energies as a probe for their reactivity. The DFT results confirmed the predictions of the d-band model, thus providing guidance for a rational modification of the chemical properties of early transition metals. [1] M. Mavrikakis, B. Hammer, and J.K. Nørskov, Phys. Rev. Lett. 81, 2819 (1998).