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Title: Anomalous random correlations of force constants on the lattice dynamical properties of disordered Au-Fe alloys

Here, gold iron (Au-Fe) alloys are of immense interest due to their biocompatibility, anomalous Hall conductivity, and applications in various medical treatments. However, irrespective of the method of preparation, they often exhibit a high level of disorder with properties sensitive to the thermal or magnetic annealing temperatures. We calculate the lattice dynamical properties of Au 1–xFe x alloys using density functional theory methods where, being multisite properties, reliable interatomic force constant (IFC) calculations in disordered alloys remain a challenge. We follow a twofold approach: an accurate IFC calculation in an environment with nominally zero chemical pair correlations to mimic the homogeneously disordered alloy and a configurational averaging for the desired phonon properties (e.g., dispersion, density of states, and entropy). We find an anomalous change in the IFC's and phonon dispersion (split bands) near x=0.19, which is attributed to the local stiffening of the Au-Au bonds when Au is in the vicinity of Fe. Other results based on mechanical and thermophysical properties reflect a similar anomaly: Phonon entropy, e.g., becomes negative below x=0.19, suggesting a tendency for chemical unmixing, reflecting the onset of a miscibility gap in the phase diagram. Our results match fairly well with reported data wherever available.
Authors:
 [1] ;  [2] ;  [3] ;  [1]
  1. Indian Institute of Technology Bombay, Mumbai (India)
  2. Ames Lab., Ames, IA (United States)
  3. Ames Lab. and Iowa State Univ., Ames, IA (United States)
Publication Date:
Report Number(s):
IS-J-9464
Journal ID: ISSN 2469-9950; PRBMDO; TRN: US1801050
Grant/Contract Number:
AC02-07CH11358
Type:
Accepted Manuscript
Journal Name:
Physical Review B
Additional Journal Information:
Journal Volume: 96; Journal Issue: 10; Journal ID: ISSN 2469-9950
Publisher:
American Physical Society (APS)
Research Org:
Ames Laboratory (AMES), Ames, IA (United States)
Sponsoring Org:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Vehicle Technologies Office (EE-3V)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE
OSTI Identifier:
1417371
Alternate Identifier(s):
OSTI ID: 1393308

Kangsabanik, Jiban, Chouhan, Rajiv K., Johnson, D. D., and Alam, Aftab. Anomalous random correlations of force constants on the lattice dynamical properties of disordered Au-Fe alloys. United States: N. p., Web. doi:10.1103/PhysRevB.96.100201.
Kangsabanik, Jiban, Chouhan, Rajiv K., Johnson, D. D., & Alam, Aftab. Anomalous random correlations of force constants on the lattice dynamical properties of disordered Au-Fe alloys. United States. doi:10.1103/PhysRevB.96.100201.
Kangsabanik, Jiban, Chouhan, Rajiv K., Johnson, D. D., and Alam, Aftab. 2017. "Anomalous random correlations of force constants on the lattice dynamical properties of disordered Au-Fe alloys". United States. doi:10.1103/PhysRevB.96.100201. https://www.osti.gov/servlets/purl/1417371.
@article{osti_1417371,
title = {Anomalous random correlations of force constants on the lattice dynamical properties of disordered Au-Fe alloys},
author = {Kangsabanik, Jiban and Chouhan, Rajiv K. and Johnson, D. D. and Alam, Aftab},
abstractNote = {Here, gold iron (Au-Fe) alloys are of immense interest due to their biocompatibility, anomalous Hall conductivity, and applications in various medical treatments. However, irrespective of the method of preparation, they often exhibit a high level of disorder with properties sensitive to the thermal or magnetic annealing temperatures. We calculate the lattice dynamical properties of Au1–xFex alloys using density functional theory methods where, being multisite properties, reliable interatomic force constant (IFC) calculations in disordered alloys remain a challenge. We follow a twofold approach: an accurate IFC calculation in an environment with nominally zero chemical pair correlations to mimic the homogeneously disordered alloy and a configurational averaging for the desired phonon properties (e.g., dispersion, density of states, and entropy). We find an anomalous change in the IFC's and phonon dispersion (split bands) near x=0.19, which is attributed to the local stiffening of the Au-Au bonds when Au is in the vicinity of Fe. Other results based on mechanical and thermophysical properties reflect a similar anomaly: Phonon entropy, e.g., becomes negative below x=0.19, suggesting a tendency for chemical unmixing, reflecting the onset of a miscibility gap in the phase diagram. Our results match fairly well with reported data wherever available.},
doi = {10.1103/PhysRevB.96.100201},
journal = {Physical Review B},
number = 10,
volume = 96,
place = {United States},
year = {2017},
month = {9}
}