Dresden 2009 – scientific programme

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O: Fachverband Oberflächenphysik

O 25: Surfaces and films: forces, structure and manipulation

O 25.1: Talk

Tuesday, March 24, 2009, 15:00–15:15, SCH A118

Understanding surface energies of transition metals with density-functional theory — •Aloysius Soon, Martin Fuchs, and Matthias Scheffler — Fritz-Haber-Institut der MPG, Berlin, Germany

Determining index-specific surface energies of metals is, to date, still a non-trivial task, both experimentally and theoretically. Density-functional theory (DFT) calculations within the local-density approximation (LDA) for exchange-correlation (XC) have provided understanding of qualitative trends. Yet, absolute surface energies, in particular of d-metals still exhibit significant uncertainties related to the description of XC: gradient corrected functionals (GGA) which improve over the LDA for other properties often predict less accurate surface energies. This calls for a careful (re-)analysis of XC effects on surface energies, including non-local exchange and/or correlation.

Here we analyze the surface energies of 4d-metals with modern GGA functionals (PBEsol, AM05, developed to better describe bulk solids and (jellium) surfaces than the LDA and previous GGAs), using the all-electron FHI-aims code.¹ Relating the bulk cohesive energy and surface energy via a bond-cutting model we find that the modern GGAs can indeed correct the poorer results of the usual PBE-GGA but worsen the bulk cohesive energies of 4d-metals. In addition, we consider hybrid XC functionals (B3LYP, PBE0, and HSE03), using a cluster correction scheme,² and discuss the effects of including exact exchange on the calculated surface energies. 1. http://www.fhi-berlin.mpg.de/aims/; 2. Q.-M. Hu et al., Phys. Rev. Lett. 98, 176103 (2007); 99, 169903(E).