2003-2004 Colloquium Series

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NAU Physical Sciences (Bldg 19, Rm 321), Friday, 5 September 2003, 3:00 PM
(Refreshments at 2:45pm)

The Cluster Expansion Method: Accurate Energetics for 2^N Atomic Configurations on a Lattice

Volker Blum , National Renewable Energy Laboratory.

Abstract

Solid alloys and solutions are widely used from the very largest (metals) to the very smallest (semi-conductor) engineering tasks. From a theorist?s point of view, their properties can often be described by considering different atomic configurations on an underlying lattice, but thermodynamics presents a problem: There are a great many such configurations. The Cluster Expansion method attempts to map the most accurate available ab-initio methods (great accuracy for relatively few configurations with infinite time) onto an Ising-type lattice Hamiltonian (fast calculations for all configurations, based on ab-initio input).The talk describes the present status of the method, focusing on the art of ensuring the Hamiltonian's predictive power. Its capabilities both at zero and infinite temperature are illustrated for the refractory alloy system MoTa.

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