Regensburg 2007 – scientific programme

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O: Fachverband Oberflächenphysik

O 70: Methods: Atomic and Electronic Structure III

O 70.3: Talk

Friday, March 30, 2007, 10:45–11:00, H42

Exploiting “local” in local orbital based all-electron electronic structure theory: How near can we get? — •Paula Havu, Ville Havu, Patrick Rinke, Volker Blum, and Matthias Scheffler — Fritz-Haber-Institut, Faradayweg 4-6, D-14195 Berlin, Germany

Numeric atom-centered local orbitals (NAO) are efficient basis sets for all-electron electronic structure theory. A strict localization of NAOs can be exploited to render (in principle) all operations of the self-consistency cycle O(N). This is straightforward for 3D integrals using domain decomposition into spatially close subsets (“domains”) of integration points, enabling critical computational savings that are effective from ∼tens of atoms (no significant overhead for smaller systems) and make large systems (hundreds of atoms and beyond) computationally feasible. Using a new all-electron NAO-based code,[1] we investigate the quantitative impact of basis orbital localization on three distinct physical classes of systems: Extended light-element biomolecules, compact transition metal clusters, and periodic bulk/surface systems. Strictly confined NAOs are achieved by imposing a cutoff potential with an onset radius r_c, and exploited by appropriately shaped integration domains. Conventional tight r_c≤ 3Å have no measurable accuracy impact in Alanine-based polypeptides, but introduce inaccuracies of 20-30 meV/atom in Cu_n clusters. We show how a rigorous exploitation of NAO localization is critical in dense periodic systems.

[1] V. Blum, R. Gehrke, P. Havu, V. Havu, X. Ren, M. Scheffler, The FHI Ab Initio Molecular Simulations (aims) Project, Fritz-Haber-Institut, Berlin (2006).