Thermo-Calc Anwendertreffen Aachen, 3-4 September 2015

Transcription

1 Thermo-Calc Anwendertreffen Aachen, 3-4 September 2015 Thermodynamic and Transport Properties Determined from Ab Initio and Forcefield Simulations using MedeA Erich Wimmer Materials Design Materials Design, Inc. 2015

2 Outline Materials Design company profile Scientific and technological context ICME Examples Ni-Cr phase diagram Effect of alloying elements and impurities on strength of grain boundaries Interface energy Heat capacity The Zr-H system Precipitation of TiC in steel Diffusion and melting Boron carbide Viscosity of molten Ni Surface tension of molten Cu Discussion Materials Design, Inc

3 Materials Design, Company Inc. Profile Company Profile Founded in 1998 Business: MedeA software, support, and contract research Over 400 customers in Industry, Universities, and Government Laboratories including the world s largest companies in Automotive Chemical Electronics Oil and gas Energy Global: USA (San Diego, Angel Fire), Europe (Paris, Stockholm), business partners in Japan, Korea, China, Taiwan, Singapore, and India Materials Design, Inc

4 Technology Chain Design Manufacturing Reliability Experiments MedeA Atomistic Simulations Materials Properties Thermodynamics Diffusion models Microstructure FE structural analysis CFD Process models Corrosion models Device models Integrated Computational Materials Engineering: A Transformational Discipline for Improved Competitiveness and National Security, National Research Council (2008) Materials Design, Inc

5 Phase Stability in Ni-Cr Alloys CrNi 2 phase embrittles Prediction of longrange-ordered phase from atomistic simulations asdf Materials Design, Inc

6 Cr-Ni Enthalpies from Cluster Expansion MedeA -VASP-UNCLE CrNi 2 Materials Design, Inc

7 CrNi 2 Unit cell of antiferromagnetic CrNi 2 P2/m Antiferromagnetic ordering in Cr-chains is a key factor stabilizing CrNi 2 Materials Design, Inc

8 Strength of Ni Grain Boundaries Result of Computations: Ranking of Impurities and Alloying Elements MedeA -VASP Grain boundaries with impurities strengthening monocrystalline Ni Σ5 grain boundary in pure Ni weakening Materials Design, Inc

9 Interface Energy: Al/Si 3 N 4 MedeA -VASP 9

10 Heat Capacity Mg MedeA -VASP-Phonon-MT C p (T) heat capacity at constant pressure C v (T) heat capacity at constant volume α V (V,T) thermal expansion coefficient B(T). bulk modulus T. temperature V 0. volume All thermodynamic properties computed from first principles within the quasi-harmonic approximation Computed with MedeA -VASP, MedeA -Phonon, and MedeA -MT J. Wróbel, L.G. Hector, W. Wolf, S. L. Shang, Z. K. Liu, and K. J. Kurzydłowski, J. Alloys and Compounds 512, 296 (2012)

11 Zr-H Phase Diagram EOF/atom: -54 kj/mol ε-zrh 2 I4/mmm a = Å (+0.48%) c = Å (+0.21%) c 11 = 225 GPa c 12 = 88 GPa c 33 = 157 GPa c 13 = 108 GPa c 44 = 30 GPa B = 130 GPa G = 24 GPa E = 68 GPa δ-zrh 2 Fm-3m EOF/atom: -53 kj/mol a = Å (+0.92%) Elastically unstable with 1:2 stoichiometry µ S2 Zr P6_3/mmc EOF/atom: -40 kj/mol a = Å (+0.00%) c = Å (+1.50%) ZrH P4_2/mmc γ EOF/atom: -31 kj/mol a = Å (+1.23%) c = Å (+1.30%) γ-zrh I-4m2 EOF/atom: kj/mol a = Å Zr 2 H Pn-3m EOF/atom: kj/mol a = Å (-1.1%) c = Å (+5.2%) ζ-zr 2 H P-3m1 Materials Design, Inc

12 Elastic Properties of ZrH x MedeA provides properties where experimental data are lacking MedeA -VASP-MT Materials Design, Inc

13 Solubility of H in Zr MedeA -VASP, Phonon Computed Measured Computed Materials Design, Inc

14 Nucleation of Dislocation Loops MedeA -LAMMPS/EAM Expansion in <a> Shrinkage in <c> Consistent with experimental data on radiationinduced growth Materials Design, Inc

15 Diffusion of H in Ni MedeA -VASP, Phonon The diffusion coefficient of H in Ni computed from first-principles has similar accuracy as experimental data at ambient and medium temperatures Isotope effects are well explained and quantitatively described E. Wimmer, W. Wolf, J. Sticht, P. Saxe, C. B. Geller, R. Najafabadi, and G. A. Young, Temperature-dependent diffusion coefficients from ab initio computations: Hydrogen, deuterium, and tritium in nickel, Phys. Rev. B 77, (2008) Materials Design, Inc

16 Precipitation MedeA -VASP

17 Computed vs. Experimental Solubility Product MedeA -VASP Computed solubility product of TiC in ferritic Fe-Cr steel is similar to available experimental data Accurate electronic energies, inclusion of vibrational entropy (full phonon spectra) and thermal expansion are critical Ab initio calculations provide quantitative materials property data for alloy engineering Wolf et al. (unpublished) log[ M ][ X ] = A H T

18 Boron Carbide MedeA -VASP-UNCLE High melting point at ~ 3000 K Extremely hard (Vickers hardness 38 GPa) third hardest substance known (after diamond and boron nitride) brake linings bulletproof vests tank armor Materials Design, Inc

19 Boron Carbide MedeA -VASP-UNCLE? Distribution of carbon and boron on the lattice? How does this influence hardness? Materials Design, Inc

20 Boron Carbide Cluster Expansion MedeA -VASP-UNCLE CE for 0 at.% - 20 at.% carbon Max. 1 unit cells (15 sites) CVS: 2.4 mev/atom 14 DFT inputs, 81 CE predictions Materials Design, Inc

21 Boron Carbide Cluster Expansion MedeA -VASP-UNCLE Minimum carbon solubility in agreement with experimental phase diagram Materials Design, Inc

22 Boron Carbide Cluster Expansion + MT MedeA -VASP-UNCLE hardness B Elastic properties of the three ground state structures with MT Bulk modulus (Hill) [GPa] Young s modulus [GPa] c [GPa] c [GPa] Hardness increases with carbon concentration Materials Design, Inc

23 Phonon Dispersions of Stable B 4 C MedeA -Phonon Phonon calculations prove that the structure is dynamically stable Materials Design, Inc

24 Viscosity of Molten Ni MedeA -LAMMPS Materials Design, Inc

25 Cu Surface Tension with MedeA-LAMMPS Surface tension using a slab model and an EAM (Zhou 2004) forcefield MedeA -LAMMPS ³ = L z (P N -P T ) where L z is the slab dimension in z, and P N and P T the mean normal and tangential pressure components respectively Experimental data from Matsumoto et al, JWRI 34, 29 (2005) Materials Design, Inc

26 Thermal Conductivity MedeA -LAMMPS-Transport Computational approach: Supercell containing 7605 atoms Reverse non-equilibrium molecular dynamics: set heat flux, compute temperature gradient 400 ps equilibration, 1 ns data collection Newly developed charge-optimized many-body (COMB3) forcefield [1] MedeA-LAMMPS Calculations performed on CRAY XC-40 using 640 cores; computing time approximately 24 hours 1. France-Lanord et al., to be published Materials Design, Inc

27 Materials Properties from Computations Structural properties Density crystalline, amorphous, liquid Bond distances bulk, surfaces, interfaces Point defects Stacking faults Grain boundaries Dislocations Thermo-Mechanical properties Elastic moduli Speed of sound Debye temperature Stress-strain behavior Thermal expansion coefficients Thermodynamic properties U, H, S, G, heat capacity Binding energies Solubility Melting temperature Vapor pressure Miscibility Phase stability Surface tension Chemical properties Chemical reaction rates Reactivity on surfaces Solid-solid reactions Photochemical reactions Transport properties Mass diffusion coefficient Permeability Thermal conductivity Viscosity Electronic, optical, and magnetic properties Electron density distribution - electrical moments Polarizabilities, hyperpolarizabilities Optical spectra Dielectric properties Piezoelectric properties Electrostatic potential Spin density distribution, magnetic moments Energy band structure Band gaps, band offsets at hetero-junctions Effective masses Ionization energies and electron affinities Work function Materials Design, Inc

28 MedeA Materials properties from atomistic simulations