Regensburg 2016 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 19: Mechanical Properties I

MM 19.5: Vortrag

Dienstag, 8. März 2016, 11:15–11:30, H52

Stacking fault energetics of α- and γ-cerium investigated with ab initio calculations — •Andreas Östlin¹, Igor di Marco², Inka Locht², Jason Lashley^{2, 3}, and Levente Vitos^{1, 2, 4} — ¹Applied Materials Physics, Department of Materials Science and Engineering, KTH Royal Institute of Technology, Stockholm SE-100 44, Sweden — ²Department of Physics and Materials Science, Uppsala University, P.O. Box 516, SE-75120 Uppsala, Sweden — ³Los Alamos National Laboratory, P.O. Box 1663 Bikini Atoll Road, Los Alamos, New Mexico, USA — ⁴Research Institute for Solid State Physics and Optics, Wigner Research Center for Physics, Budapest H-1525, P.O. Box 49, Hungary

At ambient pressure the element cerium shows a metastable double hexagonal close-packed β-phase that is positioned between two cubic phases, γ and α. We have computed stacking fault formation energies of the cubic phases of cerium using an axial interaction model. Total energies were calculated by density functional theory (DFT) and by dynamical mean field theory (DMFT) merged with density functional theory (DMFT+DFT). It is found that there is a large difference in the stacking fault energies between the α and γ-phase. The β-phase energy is nearly degenerate with the γ-phase, consistent with previous third law calorimetry results, and dislocation dynamics explain the pressure and temperature hysteretic effects. The β-phase can be seen as a dislocation reservoir that appears to be necessary to accommodate the large strains generated during the α-γ transition.