Baden-Beden, Oct ober 2001 IEA_WS Fusion Neutronics Instituto Fusión Nuclear (DENIM) ----------- Universidad Politécnica de Madrid (UPM) Microstructure characterization of Radiation Damage of SiC, and metals under pulse irradiation, by using Multiscale Modeling J.M. Perlado 1 , D. Lodi 1,2 , M. Salvador 1, M. J. Caturla 3 , T. Díaz de la Rubia 3, L. Colombo 4 1 Instituto de Fusión Nuclear (DENIM) / Universidad Politécnica de Madrid (UPM) 2 SCK-CEN, Boeretang 200, 2400 Mol, Belgium. 3 Lawrence Livermore National Laboratory, Livermore, CA94550, USA 4 Universitá degli Studi Cagliari, Monserrato, Cagliari, Italy
Transcript
Baden-Beden, October 2001
IEA_WS Fusion Neutronics
Instituto Fusión Nuclear (DENIM)
-----------
Universidad Politécnica de Madrid (UPM)
Microstructure characterization of Radiation Damage of SiC,
and metals under pulse irradiation, by using Multiscale Modeling
J.M. Perlado1, D. Lodi1,2, M. Salvador1, M. J. Caturla3,
T. Díaz de la Rubia3, L. Colombo4
1Instituto de Fusión Nuclear (DENIM) / Universidad Politécnica de Madrid (UPM)
2 SCK-CEN, Boeretang 200, 2400 Mol, Belgium.3 Lawrence Livermore National Laboratory, Livermore, CA94550, USA
4 Universitá degli Studi Cagliari, Monserrato, Cagliari, Italy
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IEA_WS Fusion Neutronics
Instituto de fusión nuclear
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Universidad Politécnica de
MadridContents of the workContents of the work
• Pulsed Irradiation of Pulsed Irradiation of -Fe-Fe• Study in more realistic environment for IFE: - Pulse FrequencyFrequency 1 - 10 Hz1 - 10 Hz - Dose rateDose rate 0.1- 0.01 dpa/s0.1- 0.01 dpa/s
• Comparison between pulsed and continuous irradiation
• New Tight- Binding Molecular Dynamics model New Tight- Binding Molecular Dynamics model for assessing defect energetics in SiC.for assessing defect energetics in SiC.
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IEA_WS Fusion Neutronics
Instituto de fusión nuclear
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Universidad Politécnica de
Madrid Neutron Environment conditionsNeutron Environment conditions
The Absence of an appropriate Pulsed neutron source The Absence of an appropriate Pulsed neutron source make Computational Simulation an important tool for make Computational Simulation an important tool for microscopic interpretation of macroscopic effects and microscopic interpretation of macroscopic effects and for predicting the response of materials to irradiationfor predicting the response of materials to irradiation
Some proposal appear in the last few years making use Some proposal appear in the last few years making use of laser technology (Perkins et al. Nuclear Fusion of laser technology (Perkins et al. Nuclear Fusion 40/N.1 (2000) 1-19).40/N.1 (2000) 1-19).
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Computational tools
• SPECTER code to determine the PKA spectrum• TRIM to determine the PKA damage Energy • MDCASK (LLNL-DENIM) to study the primary
damage state (cascade), and defects energetics • BIGMAC (LLNL) to study the evolution of the
microstructure
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IEA_WS Fusion Neutronics
Multiscale Modeling up to MicroscopicMultiscale Modeling up to Microscopic
Computational tools
Transport + Kinematic codes
Binary collision code
Molecular Dynamics code
Kinetic Montecarlo code
To determine PKA damage Energy and Collisional Cascade description
To study the primary damage state and defects energetics
To study the evolution of the micro structure
To determine PKA spectrum
Informations provided
How many PKAs and with which energy
Energy transfered to the atom and geometrical distribution of the subcascades
Nº and characteristics of defects per cascade and defects energetics
Defects type and concentration
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IEA_WS Fusion Neutronics
Multiscale approach forMultiscale approach for Pulsed Irradiation Pulsed Irradiation
PKA spectrum Program that builds a PKA
Cascade data base
PKA
PULSE
The pulse has a deposition time which must be previously calculated
The Nº of PKAs forming the pulse depends on the dose dose raterate, the Pulse Pulse deposition deposition Time Time and the dimension dimension of the boxof the box
Transport codeMolecular Dynamics Code
Kinetic Montecarlo code Kinetic Montecarlo codeInput parameters of the KMC simulation are :
temperature, dose rate, dose
O.1 - 1 s
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IEA_WS Fusion Neutronics
KMC codeKMC code BIGMAC BIGMAC
Considered events1) Diffusion2) Clustering of defects of the
same type3) Dissociation from a cluster4) Annihilation of defects of the
opposite type5) Annihilation in sink6) Trapping7) New cascade8) 9)
Vacancy clusters ConcentrationVacancy clusters Concentrationvs. Pulse frequencyvs. Pulse frequency
0.0 0.2 0.4 0.6 0.8 1.00.00E+000
2.00E+015
4.00E+015
6.00E+015
8.00E+015
1.00E+016
1.20E+016
Vacancy Clusters Concentration Vs Time
10Hz 1Hz
Con
cent
ratio
n (1
/cm̂
3)
Time ( sec.)
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IEA_WS Fusion Neutronics
Vacancy clusters ConcentrationVacancy clusters Concentration during 1 Hz pulse during 1 Hz pulse
PeakAfter relaxation
0.0 0.2 0.4 0.6 0.8 1.00.00E+000
2.00E+015
4.00E+015
6.00E+015
8.00E+015
1.00E+016
1.20E+016
Vacancy clusters concentration Vs Time 1Hz Pulse
Con
cent
ratio
n ( 1
/cm̂
3)
Time ( sec.)
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IEA_WS Fusion Neutronics
ContinuContinuousous vs Pulsed vs Pulsed
Comparison between Pulsed and Continuous irradiation leads to the Comparison between Pulsed and Continuous irradiation leads to the conclusion that damage accumulation is almost identical as regard conclusion that damage accumulation is almost identical as regard to vacancy clusters densityto vacancy clusters density
Tight Binding Molecular Dynamics for SiCTight Binding Molecular Dynamics for SiC
We develop a semiempirical tight binding molecular dynamics scheme to study the defects energetics in SiC.
We justify the needWe justify the need of this scheme:
•The classical interatomic potentials used in large scale The classical interatomic potentials used in large scale simulations are poor in SiC due to its empirical naturesimulations are poor in SiC due to its empirical nature
•The computational cost of the Tight Binding methods The computational cost of the Tight Binding methods is less expensive in comparison with the ¨ is less expensive in comparison with the ¨ ab ab initio ¨ initio ¨ methodmethod, With TBMD we can obtain results of complex systems with a great friability and with more atoms in our simulations
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Tight Binding Molecular Dynamics for SiCTight Binding Molecular Dynamics for SiC
•The TBMD semiempirical method consist in to solve the Schröndinger equation where some operators are substituted by experimental results. •The TB model, is a semiempiric version of the Linear The TB model, is a semiempiric version of the Linear Combination of Atomic Orbital (LCAO) method, with a Combination of Atomic Orbital (LCAO) method, with a minimum basis functions; basically, the analysis is minimum basis functions; basically, the analysis is reduced to the problem of one particle moving in an reduced to the problem of one particle moving in an average field.average field.• The total electronic energy of the system, depends on an The total electronic energy of the system, depends on an attractive and repulsive term: attractive and repulsive term: EEtottot = E = Ebsbs + + UUreprep
Where EWhere Ebsbs is the structure energy band obtained by the is the structure energy band obtained by the
Fermi-Dirac DistributionFermi-Dirac Distribution
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Tight Binding Molecular Dynamics for SiCTight Binding Molecular Dynamics for SiC
We use a simple average for the interaction of the We use a simple average for the interaction of the Hamiltonian matrix elements.Hamiltonian matrix elements.
The on-site energies are those of Weissmann and Fu, and in The on-site energies are those of Weissmann and Fu, and in the pair interaction between Silicon and Carbon, we use a the pair interaction between Silicon and Carbon, we use a weighted average suggested by the same authors.weighted average suggested by the same authors.
In our TB scheme we can manage different atomic coordination number, chemical bonding and equilibrium distances.
We use a short-ranged repulsive term Urep, for which we We use a short-ranged repulsive term Urep, for which we adopt the functional form, suggested by Goodwin, Skinner adopt the functional form, suggested by Goodwin, Skinner and Pettifor for the scaling function and Pettifor for the scaling function s s ( ( rr ) and the pairwise ) and the pairwise potential Φ ( potential Φ ( rr ). ).
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Tight Binding Molecular Dynamics for SiC
For computing the attractive force we implement For computing the attractive force we implement the Hellmann - Feynman theorem, using the linear the Hellmann - Feynman theorem, using the linear combination and exploiting the analytical combination and exploiting the analytical dependence of the TB hopping upon the dependence of the TB hopping upon the interatomic distancesinteratomic distances.
We use for the development of the TB model, the We use for the development of the TB model, the LAPACK library for the diagonalization of the LAPACK library for the diagonalization of the Hamiltonian Matrix.Hamiltonian Matrix.
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Tight Binding Molecular Dynamics for SiCTight Binding Molecular Dynamics for SiC
We can reproduce efficiently the cohesive energies of different SiC crystalline structure.
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Tight Binding Molecular Dynamics for SiCTight Binding Molecular Dynamics for SiC
Here we shown the Energy Band Structure in a SiC Molecule in dependence of its interatomic distance
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Conclusions
• Multiscale Modeling proved by ExperimentsMultiscale Modeling proved by Experiments• Pulse Radiation DamagePulse Radiation Damage• Time between pulses is the variable that control vacancy clusters
density and size
• Frequency has no effect on Interstitials accumulation
• No significant differences between No significant differences between average average pulsed and pulsed and
continuous irradiation in the range studiedcontinuous irradiation in the range studied • New Model for Defect Energetic in SiC using Tight New Model for Defect Energetic in SiC using Tight
Binding Molecular Dynamics is starting to be Binding Molecular Dynamics is starting to be
