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Title: Phase stability, ordering tendencies, and magnetism in single-phase fcc Au-Fe nanoalloys

Bulk Au-Fe alloys separate into Au-based fcc and Fe-based bcc phases, but L1 0 and L1 2 orderings were reported in single-phase Au-Fe nanoparticles. Motivated by these observations, we study the structural and ordering energetics in this alloy by combining density functional theory (DFT) calculations with effective Hamiltonian techniques: a cluster expansion with structural filters, and the configuration-dependent lattice deformation model. The phase separation tendency in Au-Fe persists even if the fcc-bcc decomposition is suppressed. The relative stability of disordered bcc and fcc phases observed in nanoparticles is reproduced, but the fully ordered L1 0 AuFe, L1 2 Au 3Fe, and L1 2 AuFe 3 structures are unstable in DFT. But, a tendency to form concentration waves at the corresponding [001] ordering vector is revealed in nearly-random alloys in a certain range of concentrations. Furthermore, this incipient ordering requires enrichment by Fe relative to the equiatomic composition, which may occur in the core of a nanoparticle due to the segregation of Au to the surface. Effects of magnetism on the chemical ordering are also discussed.
Authors:
 [1] ;  [2] ;  [1] ; ORCiD logo [1]
  1. Univ. of Nebraska, Lincoln, NE (United States). Dept. of Physics and Astronomy, Nebraska Center for Materials and Nanoscience
  2. Univ. of Nebraska, Lincoln, NE (United States). Dept. of Physics and Astronomy, Nebraska Center for Materials and Nanoscience; Intermolecular Inc., San Jose, CA (United States)
Publication Date:
Grant/Contract Number:
SC0001269
Type:
Accepted Manuscript
Journal Name:
Physical Review B
Additional Journal Information:
Journal Volume: 96; Journal Issue: 13; Journal ID: ISSN 2469-9950
Publisher:
American Physical Society (APS)
Research Org:
Univ. of Nebraska, Lincoln, NE (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; Fe-Au alloys; phase transitions; ordering; nanoparticles; strain-induced interaction; first-principles calculations; magnetism; Kanzaki forces; force constants
OSTI Identifier:
1399581
Alternate Identifier(s):
OSTI ID: 1399641