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MM: Fachverband Metall- und Materialphysik

MM 10: Computational Materials Modelling II - Theory/Numerics

MM 10.3: Vortrag

Montag, 31. März 2014, 12:15–12:30, IFW D

Large scale supercell calculations for forces around substitutional defects in NiTi — •Rudolf Zeller — IAS-3, Forschungszentrum Jülich GmbH

Density functional calculations are used to investigate the force field arising from substitutional Ni and Cu defect atoms on Ti sites in the shape memory alloy NiTi. The forces for the unrelaxed atomic positions are calculated by the Korringa-Kohn-Rostoker (KKR) Green-function method for the experimentally found monoclinic B19' ground state structure. The force pattern in the vicinity of the defect atoms is markedly different between 32-atom and 256-atom supercells while it is nearly the same between 256-atom and 2048-atom supercells. This difference is explained by symmetry arguments and its possible implication on the concentration dependence of the transition from the high temperature B2 phase to the low temperature B19' or strain glass phases is discussed.