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Department of Computational Materials Design Düsseldorf, Germany I. Bleskov, F. Körmann, T. Hickel, and J. Neugebauer Impact of Magnetism.

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Presentation on theme: "Department of Computational Materials Design Düsseldorf, Germany I. Bleskov, F. Körmann, T. Hickel, and J. Neugebauer Impact of Magnetism."— Presentation transcript:

1 Department of Computational Materials Design Düsseldorf, Germany I. Bleskov, F. Körmann, T. Hickel, and J. Neugebauer i.bleskov@mpie.de Impact of Magnetism on Thermodynamic Properties of Iron SFB-761 “Stahl – ab initio” Sub-project A2 “Ab initio thermodynamics and kinetics”

2 FEST-VEK 2013 (MISIS), 21-22.10.2013, Moscow I. Bleskov et al., MPIE Düsseldorf Contents Motivation Methodology –ANNNI model –Explicit approach –Structures Results –Magnetic phase diagram of iron –γ-surface –twins Summary 1

3 FEST-VEK 2013 (MISIS), 21-22.10.2013, Moscow I. Bleskov et al., MPIE Düsseldorf Motivation 2

4 FEST-VEK 2013 (MISIS), 21-22.10.2013, Moscow I. Bleskov et al., MPIE Düsseldorf Motivation 3  99% of the passenger cars have a steel body  60-70% of the car weight consist of steel or steel-based parts Passive safety and Protection from  Frontal crash  Rear collision  Side impact  Roll over Weight increasing Decreasing of  Engine efficiency and economy  Environmental pollution Steels with  low weight density  high Energy-absorbtion and  strength Tend to be mutually exclusive

5 FEST-VEK 2013 (MISIS), 21-22.10.2013, Moscow I. Bleskov et al., MPIE Düsseldorf Motivation 4 Material should react only locally to failures induced by high external stress On the atomic scale this means  Changes in the atomic layers stacking sequence under the stress and gradual twin formation (TWIP) during deformation (“dynamical” Hall-Petch effect) B.C. De Cooman, Kwang-geun Chin, Jinkyung Kim Strength + Plasticity

6 FEST-VEK 2013 (MISIS), 21-22.10.2013, Moscow I. Bleskov et al., MPIE Düsseldorf Motivation 5 Atomic layers shear can take place only if the stacking fault energy (SFE), i.e. energy required to change the sequence in atomic layer stacking, lies in a specific range A. Saeed-Akbari, et al., Meta. and Mater. Trans. A 40, 3076 (2009) SFE is the crucial quantitative parameter that characterizes the type of plasticity mechanism in crystalline materials The idea that changing the SFE one can tune the mechanical properties opens an attractive way to the design of new high-strength lightweight steels

7 FEST-VEK 2013 (MISIS), 21-22.10.2013, Moscow I. Bleskov et al., MPIE Düsseldorf Motivation 6 Figure from: J. Nakano and P. J. Jacques, CALPHAD 34 (2010) 167 SFE trends  different influence of alloying elements  chemical and magnetic disorder  dependence of properties on sample preparation and microstructure Ab initio calculations allow independent consideration of the influence of different factors on the SFE High-Mn steels (austenitic fcc structure stabilized by Mn)  exceptional mechanical properties  relatively lightweight

8 FEST-VEK 2013 (MISIS), 21-22.10.2013, Moscow I. Bleskov et al., MPIE Düsseldorf Motivation 7 Local magnetism can influence different properties of a material Magnetic contribution to SFE Phonon spectrum in PM fcc Fe, F.Körmann (SFB-761) Vibrational, electronic, and magnetic contributions to the heat capacity of FM bcc Fe F.Körmann (SFB-761) But due to computational challenge, often the simpler NM calculation are performed. Reliability may be questionable in this case.

9 FEST-VEK 2013 (MISIS), 21-22.10.2013, Moscow I. Bleskov et al., MPIE Düsseldorf Motivation 8 The impact of local magnetism on the SFE in pure iron is considered because  Iron is a basis element in steels  To avoid the influence of alloying elements Magnetic orderingComputational details Nonmagnetic (NM) VASP code; PAW basis set; PBE exchange- correlation functional Ferromagnetic (FM) Antiferromagnetic (single-layer) Antiferromagnetic (double-layer) Paramagnetic EMTO + CPA code; disordered local moment (DLM) approximation (quasi- binary alloy); GGA exchange-correlation effects

10 FEST-VEK 2013 (MISIS), 21-22.10.2013, Moscow I. Bleskov et al., MPIE Düsseldorf Contents Motivation Methodology –ANNNI model –Explicit approach –Structures Results –Magnetic phase diagram of iron –γ-surface –twins Summary 9

11 FEST-VEK 2013 (MISIS), 21-22.10.2013, Moscow I. Bleskov et al., MPIE Düsseldorf Methodology. ANNNI model 10 AdvantagesDisadvantagesResults Defect-free bulk structures => Moderate computational costs Neglect of local changes of atomic/electronic structure Loss of info on segregation effects Influence of Carbon on the ISFE in steels Magnetic contribution to ISFE in ternary and quarternary Fe-based alloys and steels…

12 FEST-VEK 2013 (MISIS), 21-22.10.2013, Moscow I. Bleskov et al., MPIE Düsseldorf Methodology. Explicit approach 11 AdvantagesDisadvantagesResults Atomic relaxation, Changes in electronic structure, Segregation effects due to SF formation Energetic barriers to form a particular stacking Big supercell => High computational costs Influence of C, H (A9) on the γ-surface in Fe-based alloys…  More general approach with the supercell explicitly containing the defect  Shear of one part of the crystal with respect to another => concept of the generalized stacking fault energy (γ-) surface, where ISF is a particular point (minimum)

13 FEST-VEK 2013 (MISIS), 21-22.10.2013, Moscow I. Bleskov et al., MPIE Düsseldorf Methodology. fcc = …ABCABC… 12 Construct the cell explicitly containing …ABCABC… stacking: Face centered cubic => hexagonal with 3 atoms per cell A B C A B C

14 FEST-VEK 2013 (MISIS), 21-22.10.2013, Moscow I. Bleskov et al., MPIE Düsseldorf Methodology. Supercell structures 13 NM, FM, PMAFMSAFMD [111] [112]

15 FEST-VEK 2013 (MISIS), 21-22.10.2013, Moscow I. Bleskov et al., MPIE Düsseldorf Methodology. Supercell structures 14 NM, FM, PMAFMSAFMD [111] [112]

16 FEST-VEK 2013 (MISIS), 21-22.10.2013, Moscow I. Bleskov et al., MPIE Düsseldorf Contents Motivation Methodology –ANNNI model –Explicit approach –Structures Results –Magnetic phase diagram of iron –γ-surface –twins Summary 15

17 FEST-VEK 2013 (MISIS), 21-22.10.2013, Moscow I. Bleskov et al., MPIE Düsseldorf Phase diagram of iron 16 NM FM AFMS AFMD DLM NM@hcp High-Mn steels

18 FEST-VEK 2013 (MISIS), 21-22.10.2013, Moscow I. Bleskov et al., MPIE Düsseldorf Phase diagram of iron 17 NM FM AFMS AFMD DLM NM@hcp

19 FEST-VEK 2013 (MISIS), 21-22.10.2013, Moscow I. Bleskov et al., MPIE Düsseldorf Phase diagram of iron 18 NM FM AFMS AFMD DLM NM@hcp

20 FEST-VEK 2013 (MISIS), 21-22.10.2013, Moscow I. Bleskov et al., MPIE Düsseldorf Phase diagram of iron 19 NM FM AFMS AFMD DLM NM@hcp

21 FEST-VEK 2013 (MISIS), 21-22.10.2013, Moscow I. Bleskov et al., MPIE Düsseldorf Phase diagram of iron 20 NM FM AFMS AFMD DLM NM@hcp

22 FEST-VEK 2013 (MISIS), 21-22.10.2013, Moscow I. Bleskov et al., MPIE Düsseldorf Phase diagram of iron 21 NM FM AFMS AFMD DLM NM@hcp >0

23 FEST-VEK 2013 (MISIS), 21-22.10.2013, Moscow I. Bleskov et al., MPIE Düsseldorf Contents Motivation Methodology –ANNNI model –Explicit approach –Structures Results –Magnetic phase diagram of iron –γ-surface –twins Summary 22

24 FEST-VEK 2013 (MISIS), 21-22.10.2013, Moscow I. Bleskov et al., MPIE Düsseldorf γ-surface of fcc Fe 23

25 FEST-VEK 2013 (MISIS), 21-22.10.2013, Moscow I. Bleskov et al., MPIE Düsseldorf γ-surface of fcc Fe 24 FMLS FMHS

26 FEST-VEK 2013 (MISIS), 21-22.10.2013, Moscow I. Bleskov et al., MPIE Düsseldorf γ-surface of fcc Fe 25 FMLS FMHS AFMS

27 FEST-VEK 2013 (MISIS), 21-22.10.2013, Moscow I. Bleskov et al., MPIE Düsseldorf γ-surface of fcc Fe 26 FMLS FMHS AFMD AFMS

28 FEST-VEK 2013 (MISIS), 21-22.10.2013, Moscow I. Bleskov et al., MPIE Düsseldorf γ-surface of fcc Fe 27 FMLS FMHS AFMD AFMS DLM  The GSFE surface topology as well as the ISFE are affected by magnetism  Magnetism changes the ISF energetic barrier

29 FEST-VEK 2013 (MISIS), 21-22.10.2013, Moscow I. Bleskov et al., MPIE Düsseldorf ISF Energy 28 Absolute value of the ISFE changes considerably in magnetic phases

30 FEST-VEK 2013 (MISIS), 21-22.10.2013, Moscow I. Bleskov et al., MPIE Düsseldorf Contents Motivation Methodology –ANNNI model –Explicit approach –Structures Results –Magnetic phase diagram of iron –γ-surface –twins Summary 29

31 FEST-VEK 2013 (MISIS), 21-22.10.2013, Moscow I. Bleskov et al., MPIE Düsseldorf Twin Structure ( + magnetic mirror symmetry) 30 NM, FM, DLMAFMSAFMD [111] [112]

32 FEST-VEK 2013 (MISIS), 21-22.10.2013, Moscow I. Bleskov et al., MPIE Düsseldorf ISF and Twin Energy 31 The general rule that SFE = 2Twin is fulfilled. The difference is mainly due to the decreasing of the distance between defects in the same size supercell

33 FEST-VEK 2013 (MISIS), 21-22.10.2013, Moscow I. Bleskov et al., MPIE Düsseldorf Magnetism vs. Chemical trends of SFE (carbon) 32 T. Hickel, S. Sandlöbes, R.K.W. Marceau, A. Dick, I. Bleskov, J. Neugebauer, and D. Raabe, Acta Materialia, SUBMITTED The influence of magnetism on the SFE is not relevant for chemical trends

34 FEST-VEK 2013 (MISIS), 21-22.10.2013, Moscow I. Bleskov et al., MPIE Düsseldorf 33 B 2.2 Å 1.8 Å (002) (-111) Atomic planes mismatch on the twin boundary

35 FEST-VEK 2013 (MISIS), 21-22.10.2013, Moscow I. Bleskov et al., MPIE Düsseldorf Twin in fcc 34 [111] [112]

36 FEST-VEK 2013 (MISIS), 21-22.10.2013, Moscow I. Bleskov et al., MPIE Düsseldorf Twin γ-surface 35 [111] [112]

37 FEST-VEK 2013 (MISIS), 21-22.10.2013, Moscow I. Bleskov et al., MPIE Düsseldorf Twin γ-surface 36

38 FEST-VEK 2013 (MISIS), 21-22.10.2013, Moscow I. Bleskov et al., MPIE Düsseldorf Twin γ-surface 37

39 FEST-VEK 2013 (MISIS), 21-22.10.2013, Moscow I. Bleskov et al., MPIE Düsseldorf Twin γ-surface 38

40 FEST-VEK 2013 (MISIS), 21-22.10.2013, Moscow I. Bleskov et al., MPIE Düsseldorf Twin γ-surface 39

41 FEST-VEK 2013 (MISIS), 21-22.10.2013, Moscow I. Bleskov et al., MPIE Düsseldorf Twin γ-surface 40

42 FEST-VEK 2013 (MISIS), 21-22.10.2013, Moscow I. Bleskov et al., MPIE Düsseldorf Twin γ-surface 41  Twin γ-surface is not strongly affected by local magnetism except FMHS phase, where the minimum exists.  “Agreement” with exp. => local ordering near the twin boundary

43 FEST-VEK 2013 (MISIS), 21-22.10.2013, Moscow I. Bleskov et al., MPIE Düsseldorf Twin γ-surface (vs. pure Fe) 42

44 FEST-VEK 2013 (MISIS), 21-22.10.2013, Moscow I. Bleskov et al., MPIE Düsseldorf Twin FMHS local magnetic moments 43 Only local magnetic moments of the atoms lying in the vicinity of the defect are affected

45 FEST-VEK 2013 (MISIS), 21-22.10.2013, Moscow I. Bleskov et al., MPIE Düsseldorf Twin γ-surface 44 [111] [112]

46 FEST-VEK 2013 (MISIS), 21-22.10.2013, Moscow I. Bleskov et al., MPIE Düsseldorf AB’ stacking 45 [111] [1-21]

47 FEST-VEK 2013 (MISIS), 21-22.10.2013, Moscow I. Bleskov et al., MPIE Düsseldorf AB’ stacking 46 FM FM@AB’

48 FEST-VEK 2013 (MISIS), 21-22.10.2013, Moscow I. Bleskov et al., MPIE Düsseldorf AB’ stacking 47 FM FM@AB’

49 FEST-VEK 2013 (MISIS), 21-22.10.2013, Moscow I. Bleskov et al., MPIE Düsseldorf Contents Motivation Methodology –ANNNI model –Explicit approach –Structures Results –Magnetic phase diagram of iron –γ-surface –twins Summary 48

50 FEST-VEK 2013 (MISIS), 21-22.10.2013, Moscow I. Bleskov et al., MPIE Düsseldorf Summary Detailed magnetic phase diagram for different structures in pure Fe (fcc, hcp, AB’) => PM/AFM magnetic phase is relevant for TWIP-steels Topology of GSFE surface strongly depends on local magnetic structure Magnetism strongly influences the SFE and twin energy in pure Fe Topology of twin γ-surface doesn’t suffer strong changes subject to local magnetism changes but discovers an unexpected minimum corresponding to AB’ stacking sequence which can shad a light to atomic planes mismatch in twin and matrix observed experimentally 49

51 FEST-VEK 2013 (MISIS), 21-22.10.2013, Moscow I. Bleskov et al., MPIE Düsseldorf Outlook and Publications 50 FURTHER ACTIVITIES SFE at finite temperatures (phonons, magnons, phonons-magnons) Influence of different alloying (Mn, Al, Si) elements on the SFE Kappa-carbides Grain boundaries … RECENT PUBLICATIONS 1.I. Bleskov, T. Hickel, J. Neugebauer, Impact of local magnetism on stacking fault energies: A first principles investigation for fcc iron, (IN PREPARATION) 2.T. Hickel, S. Sandlöbes, R.K.W. Marceau, A. Dick, I. Bleskov, J. Neugebauer, and D. Raabe, Nano-diffusion controls macro-deformation of adaptive structural materials, Acta Materialia (SUBMITTED) 3.F. Körmann, B. Grabowski, P. Söderlind, M. Palumbo, S.G. Fries, T. Hickel, and J. Neugebauer, Thermodynamic modeling of chromium: strong and weak magnetic coupling, J. Phys.: Condens. Matter 25 425401 (2013) 4.F. Körmann, A. Dick, B. Grabowski, T. Hickel, and J. Neugebauer, Atomic forces at finite magnetic temperatures: Phonons in paramagnetic iron, PRB 85, 125104 (2012)

52 FEST-VEK 2013 (MISIS), 21-22.10.2013, Moscow I. Bleskov et al., MPIE Düsseldorf Thank you for your attention! 51

53 FEST-VEK 2013 (MISIS), 21-22.10.2013, Moscow I. Bleskov et al., MPIE Düsseldorf 52

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