ICAMS / Interdisciplinary Centre for Advanced Materials Simulation
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Tight-binding modelling of complex alloys: methods and challenges

Date: 26.03.2012
Place: DPG Spring Meeting 2012, Berlin, Germany

Eunan McEniry
Georg Madsen
Ralf Drautz

In order to reliably model the effects of both alloying and light elements within steels, it is essential to properly take into account the chemistry of the bonding between atoms, as well as the effects of charge transfer and magnetism. Density-functional theory provides such a reliable framework, but its computational expense places limitations on its applicability to large-scale and/or multi-component systems. The tight-binding approximation, including charge transfer and magnetism, can be derived directly from the Kohn-Sham energy functional. Since the electronic structure is obtained from a parametrised tight-binding Hamiltonian, the methodology offers an enormous computational advantage over ab-initio methods.

While many tight-binding models have obtained their parameters from density-functional calculations, they generally involve uncontrolled approximations for the matrix elements of the Slater-Koster Hamiltonian, which limits their transferability. The present work begins with the Harris-Foulkes energy functional, from which the parameters of the tight-binding model are obtained in a rigorous and umambiguous manner. We obtain transferable parametrisations of the environmental contribution to the tight-binding Hamiltonian and assess the validity of the approach by application to nickel-cobalt alloys.

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