Advanced computational multiscale materials modeling and simulation:application to radiation damages for nuclear materials and other fields

Man Yao, ProfessorSchool of Materials Science & Engineering

Dalian University of TechnologyDalian, Liaoning PR China

yaoman@dlut.edu.cn

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

Evolution of microstructure and defects

Irradiation environment: T, stress, …

Material Performance

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

Ab initio calculation

Molecular dynamic simulation (MD)

Kinetic MC methods

Mesoscopic and Continuum methods, FEM

Interatomic potentials Thermo-physical properties Fundamental properties of defects

Primary damage: Point defect, defect clustr formation and evolution

Evolution of microstructure and defects

Material Performance: thermo-mechanic behavior, plastic properties and fracture

micro

macr

o

Experiment data from neutron, electron, and ion irridiation

MMM Radiation effect

5

Ti PKA energy: 1keV (PKA-primary knock-on atom)Temperature: 500KSystem Size: 40x20x20Thermostat Layer: Outer 1 layer (Inner 38x18x18 are active region)

Blue: vacancies

Brown:interstitials

Displacement cascade -defect formation by MD

Active Region

Thermostat

6

Temperature =300 KPKA Energy = 1 KeVSystem Size = 18x18x18

Displacement cascade happens in the range of ps and nm.

Number of defects versus time

Things we are doing for radiation effect

Conducting the modeling by

• ab initio (first principle) based on quantum mechanics

• FEM in macroscopic scale for thermo-mechanic 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 self-assembly supramolecule

• Doped anatase TiO2 to shorten the energy gap for higher photocatalysis activity

• Thermo-mechanic behavior for steel

• Phonon-defect scattering in doped Si

self-assembly oriented by molecular conformation and alkyl chain

Electronic property and thermal stability

of graphene and its self-assemble supramolecule

Graphene- graphite subunit, 2D material, a new discoveredMaterial after nanotube

Properties- stable structure, good electrical and optical Conductivity, good flexibility

upupdowndown

Energy gap comparison of triangular AGNR, independent FTBC-C4 and FTBC-C4 self-assemble supramolecule

Comparison of experimental and computational STM image of

graphene-based self-assemble supramolecule

Electronic

structure

change at

353K

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]

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,Jin-Long Yang 2008 PNAS 105 16849

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

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

O Ti N

Thermo-mechanic behavior for steel By FEMThe coupled heat transfer and stress model is applied to dynamic secondary cooling and soft reduction.

Crack prediction for continuous casting of round billet

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.