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  Atomic scale configuration of planar defects in the Nb-rich C14 Laves phase NbFe2

Šlapáková, M., Zendegani, A., Liebscher, C. H., Hickel, T., Neugebauer, J., Hammerschmidt, T., et al. (2020). Atomic scale configuration of planar defects in the Nb-rich C14 Laves phase NbFe2. Acta Materialia, 183, 362-376. doi:10.1016/j.actamat.2019.11.004.

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Šlapáková, M.1, Author
Zendegani, A.1, Author
Liebscher, C. H.1, Author
Hickel, T.1, Author
Neugebauer, J.1, Author
Hammerschmidt, T.1, Author
Ormeci, A.2, Author              
Grin, J.3, Author              
Dehm, G.1, Author
Kumar, K.S.1, Author
Stein, F.1, Author
1External Organizations, ou_persistent22              
2Chemical Metal Science, Max Planck Institute for Chemical Physics of Solids, Max Planck Society, ou_1863405              
3Juri Grin, Chemical Metal Science, Max Planck Institute for Chemical Physics of Solids, Max Planck Society, ou_1863413              


Free keywords: Atoms; Binary alloys; Calculations; Charge transfer; Chemical analysis; Chemical bonds; Crystal atomic structure; Defects; High resolution transmission electron microscopy; Iron alloys; Scanning electron microscopy; Stability criteria, Ab initio calculations; Aberration-corrected scanning transmission electron microscopies; Atomic configuration; Homogeneity range; Intermetallic phasis; Laves-phase; Scanning transmission electron microscopy; Stable Configuration, Density functional theory
 Abstract: Laves phases belong to the group of tetrahedrally close-packed intermetallic phases, and their crystal structure can be described by discrete layer arrangements. They often possess extended homogeneity ranges and the general notion is that deviations from stoichiometry are accommodated by anti-site atoms or vacancies. The present work shows that excess Nb atoms in a Nb-rich NbFe2 C14 Laves phase can also be incorporated in various types of planar defects. Aberration-corrected scanning transmission electron microscopy and density functional theory calculations are employed to characterize the atomic configuration of these defects and to establish stability criteria for them. The planar defects can be categorized as extended or confined ones. The extended defects lie parallel to the basal plane of the surrounding C14 Laves phase and are fully coherent. They contain the characteristic Zr4Al3-type (O) units found in the neighboring Nb6Fe7 µ phase. An analysis of the chemical bonding reveals that the local reduction of the charge transfer is a possible reason for the preference of this atomic arrangement. However, the overall layer stacking deviates from that of the perfect µ phase. The ab initio calculations establish why these exceptionally layered defects can be more stable configurations than coherent nano-precipitates of the perfect µ phase. The confined defects are observed with pyramidal and basal habit planes. The pyramidal defect is only ~1 nm thick and resembles the perfect µ phase. In contrast, the confined basal defect can be regarded as only one single O unit and it appears as if the stacking sequence is disrupted. This configuration is confirmed by ab initio calculations to be metastable. © 2019


Language(s): eng - English
 Dates: 2020-01-032020-01-03
 Publication Status: Published in print
 Pages: -
 Publishing info: -
 Table of Contents: -
 Rev. Type: -
 Identifiers: DOI: 10.1016/j.actamat.2019.11.004
 Degree: -



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Title: Acta Materialia
  Abbreviation : Acta Mater.
Source Genre: Journal
Publ. Info: Kidlington : Elsevier Science
Pages: - Volume / Issue: 183 Sequence Number: - Start / End Page: 362 - 376 Identifier: ISSN: 1359-6454
CoNE: https://pure.mpg.de/cone/journals/resource/954928603100