Advanced Multi Scale Computational Modeling And Simulation

Advanced computational multiscale materials modeling and simulation: application to radiation damages for nuclear materials and other fields Man Yao, Professor School of Materials Science & Engineering Dalian University of Technology Dalian, Liaoning PR China [email protected] Oct 17 2009 Changzhou, China

Multiscale Materials Modeling (MMM) and simulation • MMM has now taken on the meaning of theory and simulation of materials properties and behavior across length and time scales from the atomistic to the macroscopic. • MMM– a “virtual instrument”, the output depends on the model and the input. • MMM -- conducting computational experiment over long length and time scale that so far no single real instrument can do.

Radiation effect - a typical multiscale length and time scale issue Radiation: neutron, electron, fusion and fission products, ions… Atomic displacement cascade and electron excitation Primary damage: PKA, Point defects… Defect cluster formation and evolution

Irradiation environment: T, stress, …

Evolution of microstructure and defects Material Performance

Radiation sources—primary recoil atoms—collision cascade—sources for defects and defect clusters

MMM

Radiation effect

micro macro

Ab initio calculation

Interatomic potentials Thermo-physical properties Fundamental properties of defects

Molecular dynamic simulation (MD)

Primary damage: Point defect, defect clustr formation and evolution

Kinetic MC methods

Evolution of microstructure and defects

Mesoscopic and Continuum methods, FEM

Material Performance: thermomechanic behavior, plastic properties and fracture

Experiment data from neutron, electron, and ion irridiation

Displacement cascade -defect formation by MD Ti

PKA energy: 1keV (PKA-primary knock-on atom) Temperature: 500K System Size: 40x20x20 Thermostat Layer: Outer 1 layer (Inner 38x18x18 are active region) Blue: vacancies Brown:interstitials

Active Region

Thermostat

5

Number of defects versus time

Temperature =300 K PKA Energy = 1 KeV System Size = 18x18x18

Displacement cascade happens in the range of ps and nm. 6

Things we are doing for radiation effect Conducting the modeling by • ab initio (first principle) based on quantum mechanics • FEM in macroscopic scale for thermomechanic behavior Focusing on the structure materials in fusion and fission energy system: Fe,Fe-Cr alloy, Zr and Ti etc.

Issues we concern on radiation effect 1) Transient behavior and defect formation under radiation 2) Effect of grain boundary on formation and migration of radiated interstitials and vacancies 3) Displacement damage in nanocrystalline nuclear materials 4) Characterization of radiated defects and dependency on effective factors such as grain size, PKA energy.

Other application results of MMM • Graphene and graphene-based selfassembly supramolecule • Doped anatase TiO2 to shorten the energy gap for higher photocatalysis activity • Thermo-mechanic behavior for steel • Phonon-defect scattering in doped Si

Electronicpropertyandthermal stability ofgrapheneanditsself-assemblesupramolecule down

up

self-assembly oriented by molecular conformation and alkyl chain

Graphene- graphite subunit, 2D material, a new discovered Material after nanotube Properties- stable structure, good electrical and optical Conductivity, good flexibility Energy gap comparison of triangular AGNR, independent FTBC-C4 and FTBC-C4 self-assemble supramolecule

Comparisonofexperimental andcomputational STMimageof graphene-basedself-assemblesupramolecule

STM image of FTBC-C4 self-assemble Supramolecule. A -down ,B- up conformation[1]

LUMO of FTBC-C4 self-assemble supramolecule

STM image of FTBC-C4 self-assemble supramolecule [1]

Electronic structure changeat 353K

Calculated STM images of FTBC-C4 self-assembly supramolecular. （ a ）（ b ）（ c ）（ d ） :0K,298K ， 333K ， 353K;A-down,B-up

Calculated STM images of FTBC-C6 self-assemble supramolecule. （ a ）（ b ）（ c ） （ d ） :0K,298K ， 333K ， 353K

[1]Qing Chen ， Ting Chen Ge-Bo Pan, Hui-Juan Yan, Wei-Guo Song, Li-Jun Wan,Zhong-Tao Li, Zhao-Hui Wang,Bo Shang, Lan-Feng Yuan,JinLong Yang 2008 PNAS 105 16849

O

Ti

N

Density of state (DOS) of un-doped and doped anatase TiO2

Band structure of un-doped and N-doped TiO2

After doping N, •changed band structure ; •smaller band gap (2.20 to 1.78eV); •higher photocatalysis activities under visible light condition.

T-DOS of N-doped and un-doped TiO2

Thermo-mechanic behavior for steel By FEM Crack prediction for continuous casting of round billet

The coupled heat transfer and stress model is applied to dynamic secondary cooling and soft reduction.

lattice thermal conductivity phonon-defect scattering in doped Si by MD

The lattice thermal conductivity is strongly affected by phonon wavelength, dopant concentration and atomic mass of dopants. M. Yao, T. Watanabe, P. K. Schelling, P. Keblinski, D. G. Cahill, S. R. Phillpot, Journal of Applied Physics. 104, 024905 (2008)

Thanks for your kind attention.