Yang Hu, Jennifer D. Schuler and Timothy J. Rupert. Dept. of Chemical Engineering and Materials Science, Dept. of Mechanical and Aerospace Engineering.
Identifying interatomic potentials for the accurate modeling of interfacial segregation and structural transitions Yang Hu, Jennifer D. Schuler and Timothy J. Rupert Dept. of Chemical Engineering and Materials Science, Dept. of Mechanical and Aerospace Engineering University of California, Irvine
Motivation • Complexions are thermodynamically stable interfacial phases.
Complexion transition in Cu-Ag system
• Atomistic simulations are ideal to study complexions because they: 1. work in appropriate time and length scales, 2. produce results with great details and 3. are less time-consuming as compared to real experiments. The reliability of atomistic simulation depends on the description of atomic interactions • Interaction among atoms in simulations is described by interatomic potentials which are fitted to real material’s properties. e-
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0.02 at.% Ag, 900 K
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Σ5 (210) grain boundary (GB)
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T. Frolov, et al. Phys. Rev. B, 92 (2015)
Crack nucleation and growth observed during shear deformation in samples with clean grain boundaries (GBs) and amorphous intergranular films (AIFs)
• Here, we examine four different interatomic potentials for Cu-Zr system. • This system is in our primary focus due to a high interfacial segregation of Zr that may be followed by structural transition. Z. Pan and T.J. Rupert Acta Mater., 89 (2015)
Methods and Results
4 nm
Doped GBs obtained by different potentials
Software: LAMMPS Hybrid Monte Carlo / Molecular Dynamics method Material: Bicrystalline Cu or Ni with two Σ5 (310) GBs doped with 0-10 at.% Zr atoms at 600 K or 1000 K Simulation Box Size: About 23 x 11 x 4 nm, ~100,000 Atoms Interatomic Potentials: ZJW [1], X.W. Zhou, R.A. Johnson, H.N.G. Wadley, Phys. Rev. B, 69 (2004); WAFW [2], L. Ward, A. Agrawal, M.K. Flores, W. Windl, arXiv preprint arXiv:1209.0619 (2012); CSM [3], Y.Q. Cheng, H. Sheng, E. Ma, Phys. Rev. B, 78 (2008); MKOSYP [4], M.I. Mendelev, M.J. Kramer, R.T. Ott, D.J. Sordelet, D. Yagodin, P. Popel, Philos. Mag. 89 (2009). Interatomic potential for Ni-Zr system [6] obtained from: https://sites.google.com/site/eampotentials/
In the left panels chemical information is shown, Cu Zr
6 5 4 3 2 1 0
GB
0.4 at.% Zr at 600 K 4.0 at.% Zr at 1000 K ZJW[1] Potential
1 nm
1 nm
WAFW[2] Potential
1 nm
CSM[3] Potential
Clean Σ5 (310) GB 1 nm
1 nm
MKOSYP[4] Potential
In the right panels structural information is shown, fcc other ico bcc
Enthalpies of mixing of Cu-Zr system Accurately reproducing physical quantities like enthalpy of mixing and solute solubility leads to better descriptions about the interfacial segregation and structural transition.
1 nm
Ni-Zr system simulated by a CSM potential [6] Our work can be extended to other alloy systems like Ni-rich alloys. 5.0 at.% Zr at 1000 K 0.4 at.% Zr at 600 K
0 Enthalpy of mixing (eV/atom)
Enthalpy of Mixing (eV/atom)
[5]
0.002
10 0
0
2
4 8 10 12 6 Position (nm)
1 nm
6 5 4 3 2 1 0 20 15 10 5 0
4 6 8 10 12 2 Zr Concentration (at.%)
• CSM potential and MKOSYP potential provide physical results that are closer to experiments. • Accurate modeling of interfacial segregation and structural transition requires accurately reproducing some physical quantities such as enthalpy of mixing and solute solubility. • In Ni-Zr system, there is also Zr interfacial segregation and structural transition to AIFs as doping concentration increases.
9.0 at.% Zr at 1000 K
0 -0.002 -0.004
WAFW 0 5 10 15 20 Zr Concentration (at.%)
[5] M. Turchanin, Powder Metall. -0.8 20 40 60 80 100 Met. C+, 36 0 Zr Concentration (at.%) (1997).
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20
Conclusions
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1 nm
hcp
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Complexion transition diagram for CSM potential
Discussion
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60
20 40 Position (nm)
Film thickness (nm)
Computational methods
Zr Concentration (at.%)
Experimental results are provided to validate different potentials. Sputter deposition: Cu-Zr alloy films (4.3 at.% Zr) Anneal: 500 °C for 24 h under vacuum Complexion formation: 900 °C for 1 min under vacuum with immediate quenching Material characterization: High-resolution transmission electron microscopy and energy dispersive X-ray spectroscopy technique
Cu-Zr EDS Line Scan
Zr concentration profile across the GB obtained by different potentials Zr Concentration (at.%)
A nanoscale complexion in Cu-Zr system
GB Concentration of Zr (at.%)
Experimental methods
Acknowledgements This research was supported by U.S. Department of Energy, Office of Basic Energy Sciences, Materials Science and Engineering Division under Award No. DE-SC0014232.
