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First-principles prediction of the stacking fault energy of gold at finite temperature
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. KTH Royal Inst Technol, Dept Mat Sci & Engn, Appl Mat Phys, SE-10044 Stockholm, Sweden..
KTH Royal Inst Technol, Dept Mat Sci & Engn, Appl Mat Phys, SE-10044 Stockholm, Sweden..
2017 (English)In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 135, p. 88-95Article in journal (Refereed) Published
Abstract [en]

The intrinsic stacking fault energy (ISFE) gamma is a material parameter fundamental to the discussion of plastic deformation mechanisms in metals. Here, we scrutinize the temperature dependence of the ISFE of Au through accurate first-principles derived Helmholtz free energies employing both the super cell approach and the axial Ising model (AIM). A significant decrease of the ISFE with temperature, -(36-39) % from 0 to 890 K depending on the treatment of thermal expansion, is revealed, which matches the estimate based on the experimental temperature coefficient d gamma/dT closely. We make evident that this decrease predominantly originates from the excess vibrational entropy at the stacking fault layer, although the contribution arising from the static lattice expansion compensates it by approximately 60%. Electronic excitations are found to be of minor importance for the ISFE change with temperature. We show that the Debye model in combination with the AIM captures the correct sign but significantly underestimates the magnitude of the vibrational contribution to gamma(T). The hexagonal close-packed (hcp) and double hcp structures are established as metastable phases of Au. Our results demonstrate that quantitative agreement with experiments can be obtained if all relevant temperature-induced excitations are considered in first-principles modeling and that the temperature dependence of the ISFE is substantial enough to be taken into account in crystal plasticity modeling. (C) 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Place, publisher, year, edition, pages
Elsevier, 2017. Vol. 135, p. 88-95
Keywords [en]
Stacking-fault energy, Temperature dependence, Density-functional theory
National Category
Condensed Matter Physics
Identifiers
URN: urn:nbn:se:uu:diva-335239DOI: 10.1016/j.actamat.2017.06.009ISI: 000407536800010OAI: oai:DiVA.org:uu-335239DiVA, id: diva2:1162793
Available from: 2017-12-05 Created: 2017-12-05 Last updated: 2017-12-05Bibliographically approved

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