1 / 39

Simulaciones de intercaras metálicas con DFT

Simulaciones de intercaras metálicas con DFT. C. González IFIMAC-UAM. Outline. Motivation DFT: Details of the calculation Creating an Interface: Cu/ Nb -KS He and Vacancies on Cu/ Nb and Cu/W interfaces H, Vacancies and He on W grain boundaries Conclusions. Motivation.

mrenee
Download Presentation

Simulaciones de intercaras metálicas con DFT

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Simulaciones de intercaras metálicas con DFT C. González IFIMAC-UAM

  2. Outline • Motivation • DFT: Details of the calculation • Creating an Interface: Cu/Nb-KS • He and Vacancies on Cu/Nb and Cu/W interfaces • H, Vacancies and He on W grain boundaries • Conclusions.

  3. Motivation Future fusion energy reactor. Metallic multilayers proposed in the first wall: Cu/Nb-Cu/W. Analysis of the defects: He atoms, vacancies and SIAS in the system.

  4. Modelización Multiescala Continuum Tiempo [s] simulaciones Dislocation Dynamics 5 mm 10000 segmentss 100 10-3 10-6 10-9 10-12 10-15 Kinetic Monte Carlo 1 mm 1000s Molecular Dynamics 1.2 millionatoms 24 nm 100 ps TEM, SEM, XRD ab initio 102-103atoms 1.3 nm validación experimental HRTEM Longitud [m] 10-10 10-9 10-6 10-3 100

  5. Introduction to DFT Schrödinger equation (Quantum Mechanics) Approximations: Born-Oppenheimer: Separates electrons and ions Electron treated QM as a electronic density Khon-Sham equations and one electron approx: Pseudo-potential: only valence electrons in the calculation

  6. Introduction to DFT Schrödinger equation (Quantum Mechanics) Basis: LCAO: atomic like orbitals: Faster Plane waves: More precision

  7. Introduction to DFT Initial density in Potential Vin Solving the KS equations Final density out No Self-consistency in electron density? yes Calculation of energy and forces No Self-consistency in forces and/or energy Yes Ground State

  8. Details of the calculation • DFT calculations performed with VASP. • PBE exchange and correlation functional. • VASP-PAW pseudopotentials. • Cutoff energy: 479 eV (He atoms) • Migration energies calculated with NEB technique

  9. Details of the calculation • Formation and binding energies expressions:

  10. Introduction KS interface TEM experiments M.J. Demkowicz and R.G. Hoagland JNM 372 45 (2008) A. Misra, M.J. Demkowicz, X. Zhang and R.G. Hoagland, JOM 2007

  11. Introduction TEM experiments M. J. Demkowicz et al Cur. Op. Sol. St. Mat. Sci16, 101 (2012) He at the interfaces

  12. Introduction MD and kMC simulations MD calculations good for one (two) elements. Problems with the potential generation for three elements Parametrized with bulk or MD data A. Y. Dunn et al J. Nucl. Mater. 435, 141 (2013) M. J. Demkowicz et al Cur. Op. Sol. St. Mat. Sci16, 101 (2012)

  13. The perfect crystal • FCC structure: Cu • BCC structure: Nb A Surface is created when the bulk is truncated Interface is created whit two different surfaces

  14. Searching for a good interface 1 layer of each metal and rotate one against the other Find the possible periodicities: are they available for DFT? L. A. Zotti, Sanvito, and D. D. O'Regan, A simple descriptor for energetics at fcc-bcc metal interfaces, A simple descriptor for energetics at fcc-bcc metal interfaces, Mater. Des. 142 (2018) 158. Future meeting about metallic interfaces??

  15. Searching for a good interface Cu/Nb KS interface DFT can be a guide for MD for larger reconstructions

  16. The Cu/Nb-KS interface (110) • 6 layers of each metal • Cu periodicity: 9x6 (324 at) • Nb periodicity: 8x5 (240 at) • 9 kpoints in the superficial 1BZ • Lastlayers are fixed (111)

  17. DFT results (110) (111) Strong reconstruction at interface but no Cu-Nb mixing Corrugation: Cu/Nb 0.6/0.3 Å

  18. DFT results C. González et al PHYSICAL REVIEW B 91, 064103 (2015) Nb-1st Nb-2nd Cu-1st Cu-2nd He2 He1 V Vacancies and He atoms are introduced at the interface Most stable sites for vacancy formation and He implantation are in the area where Nb and Cu atoms collide

  19. DFT results 3.90 2.5 3.0 Ef (eV) 0.726eV PNEB 2.5 0 5 15 20 10 X (Å)

  20. DFT results C) Nb 2 V Ef(eV) 1 Cu Cu in Nb layer 0 0 5 15 20 10 X (Å)

  21. DFT results: Cu vacancy 1.26 eV Cu 0.623eV

  22. DFT results: Nb vacancy • 3 ways of migration • Pure Nb atom • Cu in Cu layer • Cu in Nb layer 0.720eV Nb 0.840eV Cu vacancy 0.69eV Cu in Nb layer

  23. DFT results: He+vacancy Cu-1st Cu-2nd Nb-1st Nb-2nd He2 He1 V He prefers the vacancy instead of the Interface HeV at second layer tends to bulk values

  24. Conclusions Cu/Nb interface analyzed with DFT: • Strong reconstruction but no Cu/Nb mixing. • Defects formed preferentially in the areas of Cu-Nb atomic coincidence • Defects prefer the Interface instead of the bulk. • He prefers the vacancy instead of the Interface. • Defects have to cross high barriers in the Interface. Continuation in: U Saikia, MB Sahariah, C González, R Pandey, Scientific Reports 8, 3844 (2018)

  25. Two Cu/W-interfaces Materials and Design 91 (2016) 171–179 a) b)

  26. DFT relaxation a) b)

  27. DFT relaxation b) a) He1 He2 V V V

  28. Nucl. Fusion 55 (2015) 113009 W GB: (110)/(112) C. Gonzalez et al Nucl. Fusion 55 (2015) 113009 a) b) Experimentalmente: Predominio de orientación (110), seguidas de (112) Acumulación de H en GB’s

  29. W GB: (110)/(112) C. Gonzalez et al Nucl. Fusion 55 (2015) 113009

  30. W GB: (110)/(112) C. Gonzalez et al Nucl. Fusion 55 (2015) 113009

  31. W GB: (110)/(112) C. Gonzalez et al Nucl. Fusion 55 (2015) 113009 • H no deforma la zona alrededor • V mas favorables cuando hay átomos enfrentados • H no ocupa la vacante (como en volumen) pero se coloca cerca • Los tres casos son mas estables que en volumen • H y V migran a lo largo de las cadenas

  32. W GB: (110)/(112) X-dir He5 He3 Y-dir He4 He2 He1 • He prefers the same row as H where the charge energy is lower with open spaces • He accumulates on the vacancy Z-dir X-dir

  33. W GB: (110)/(112) a) b) c) d) e) f) Up to 7 He atoms inside a vacancy, then they start to be placed on the closer row

  34. W GB: (110)/(112) 3He 2He 1He Migration energies are higher than in the bulk Increases with the size of the bulk

  35. W GB: (110)/(112) Energy for the cluster separation is larger than the cluster migration

  36. Conclusions • Complex DFT-simulations for several metallic interfaces performed • Defects move to the interfaces • Different mobility depending on the defect and the interface • He tends to accumulate in the vacancies at the interface Future work He+H complexes FIREBALL+AMBER can be useful?

  37. People C. Guerrero G. Valles N. Gordillo M. Panizo A. Rivera R. González-Arrabal J. M. Perlado R. Iglesias M. A. Cerdeira D. Fernández-Pello MIT M. Demkowitz U. Tartu A. Tamm E. Metsanurk • Aabloo M. Klintenberg IMDEA Materiales I. Martín Bragado L. Agudo

  38. Thank you for your attention!!

  39. DFT results: Summary [1] MJ Demkowicz & L. Thilly, ActaMateralia59 7744 (2011)

More Related