Center for Molecular Modeling - P. Grigorev

Dislocation mechanism of deuterium retention in tungsten under plasma implantation

alex — Tue, 19 Aug 2014 11:54:30 +0000

V. Dubinko, D. Terentyev, P. Grigorev, A. Bakaev, G. Van Oost, F. Gao, D. Van Neck, E. Zhurkin

Journal of Physics: Condensed Matter

26, 395001

2014

Abstract

We have developed a new theoretical model for deuterium (D) retention in tungsten-based alloys on the basis of its being trapped at dislocations and transported to the surface via the dislocation network with parameters determined by ab initio calculations. The model is used to explain experimentally observed trends of D retention under sub-threshold implantation, which does not produce stable lattice defects to act as traps for D in conventional models. Saturation of D retention with implantation dose and effects due to alloying of tungsten with, e.g. tantalum, are evaluated, and comparison of the model predictions with experimental observations under high-flux plasma implantation conditions is presented.

DOI

http://dx.doi.org/10.1088/0953-8984/26/39/395001

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14_JPhysCondensMatter_26,395001_Dubinko.pdf

Atomistic simulation of the interaction between mobile edge dislocations and radiation-induced defects in Fe-Ni-Cr austenitic alloys

alex — Tue, 19 Aug 2014 11:46:20 +0000

A. Bakaev, D. Terentyev, P. Grigorev, E. Zhurkin

JOURNAL OF SURFACE INVESTIGATION-X-RAY SYNCHROTRON AND NEUTRON TECHNIQUES

8 (2), 220-228

2014

Abstract

The classical molecular dynamics method is employed to simulate the interaction of edge dislocations with interstitial Frank loops (2 and 5 nm in diameter) in the Fe-Ni₁₀-Cr₂₀ model alloy at the temperatures T = 300–900 K. The examined Frank loops are typical extended radiation-induced defects in austenitic steels adapted to nuclear reactors, while the chosen triple alloy (Fe-Ni₁₀-Cr₂₀) has the alloying element concentration maximally resembling these steels. The dislocation-defect interaction mechanisms are ascertained and classified, and their comparison with the previously published data concerning screw dislocations is carried out. The detachment stress needed for a dislocation to overcome the defect acting as an obstacle is calculated depending on the material temperature, defect size, and interaction geometry. It is revealed that edge dislocations more efficiently absorb small loops than screw ones. It is demonstrated that, in the case of small loops, the number of reactions accompanied by loop absorption increases with temperature upon interaction with both edge and screw dislocations. It is established that Frank loops are stronger obstacles to the movement of screw dislocations than to the movement of edge ones.

DOI

http://dx.doi.org/10.1134/S1027451014020062

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14_JofSurfaceInvestigation_8(2)220_Bakaev.pdf

Deuterium accumulation in tungsten under low-energy high-flux plasma exposure

alex — Tue, 19 Aug 2014 11:40:02 +0000

P. Grigorev, V. Dubinko, D. Terentyev, A. Bakaev, E. Zhurkin

JOURNAL OF SURFACE INVESTIGATION-X-RAY SYNCHROTRON AND NEUTRON TECHNIQUES

8 (2), 234–238

2014

Abstract

The accumulation of deuterium implanted in tungsten is simulated within the framework of kinetic diffusion theory. The influence of the tungsten microstructure (dislocation density and impurity concentration) on the process of deuterium capture and accumulation is considered. It is established that, under the chosen irradiation conditions, deuterium accumulation in the near-surface region is determined by capture at defects formed during implantation. The deuterium concentration gradient, together with the material microstructure, determines its accumulation in tungsten. Variation in the dislocation density and impurity concentration does not affect the simulation results, which is, first, related to the fact that the model used does not contain alternative mechanisms for the formation and growth of vacancy clusters under the subthreshold irradiation mode. The simulation results are compared with experimental data, and ways of improving the model are discussed in order to explain the deuterium-saturation effect for high fluences (more than 10²³ m⁻²).

DOI

http://dx.doi.org/10.1134/S102745101402013X

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14_JofSurfaceInvestigation_8(2)234_Grigorev.pdf

Molecular 7 dynamics simulation of the interaction of dislocations with radiation-induced defects in Fe-Ni-Cr austenitic alloys

alex — Tue, 19 Aug 2014 11:34:02 +0000

A. Bakaev, D. Terentyev, E. Zhurkin, P. Grigorev

JOURNAL OF SURFACE INVESTIGATION-X-RAY SYNCHROTRON AND NEUTRON TECHNIQUES

7 (2), 211-217

2013

Abstract

A classical molecular dynamics method is used to theoretically study the interaction of dislocations with typical radiation-induced defects in an Fe-Ni10-Cr20 austenitic alloy. As a result, a set of interactions and the corresponding values for the critical stress required for unpinning of a dislocation from an obstacle are obtained for different temperatures and interaction geometries.

DOI

http://dx.doi.org/10.1134/S1027451013020067

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13_JSurfaceInvestigation_7(2)211_Bakaev.pdf

Review of many-body central force potentials for tungsten

alex — Tue, 19 Aug 2014 11:23:22 +0000

G. Bonny, D. Terentyev, A. Bakaev, P. Grigorev, D. Van Neck

Modelling and Simulation in Materials Science and Engineering

22, 053001

2014

Abstract

Tungsten and tungsten-based alloys are the primary candidate materials for plasma facing components in fusion reactors. The exposure to high-energy radiation, however, severely degrades the performance and lifetime limits of the in-vessel components. In an effort to better understand the mechanisms driving the materials' degradation at the atomic level, large-scale atomistic simulations are performed to complement experimental investigations. At the core of such simulations lies the interatomic potential, on which all subsequent results hinge. In this work we review 19 central force many-body potentials and benchmark their performance against experiments and density functional theory (DFT) calculations. As basic features we consider the relative lattice stability, elastic constants and point-defect properties. In addition, we also investigate extended lattice defects, namely: free surfaces, symmetric tilt grain boundaries, the 1/2〈1 1 1〉{1 1 0} and 1/2〈1 1 1〉 {1 1 2} stacking fault energy profiles and the 1/2〈1 1 1〉 screw dislocation core. We also provide the Peierls stress for the 1/2〈1 1 1〉 edge and screw dislocations as well as the glide path of the latter at zero Kelvin. The presented results serve as an initial guide and reference list for both the modelling of atomically-driven phenomena in bcc tungsten, and the further development of its potentials.

DOI

http://dx.doi.org/10.1088/0965-0393/22/5/053001

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14_ModellingSimulMaterSciEng_22,053001_Bonny.pdf

Dislocations mediate hydrogen retention in tungsten

wim — Fri, 13 Jun 2014 10:11:00 +0000

D. Terentyev, V. Dubinko, A. Bakaev, Y. Zayachuk, W. Van Renterghem, P. Grigorev

Nuclear Fusion

54 (4), 042004

2014

Abstract

In this letter, a comprehensive mechanism for the nucleation and growth of bubbles on dislocations under plasma exposure of tungsten is proposed. The mechanism reconciles long-standing experimental observations of hydrogen isotopes retention, essentially defined by material microstructure, and so far not fully explained. Hence, this work provides an important link to unify material's modelling with experimental assessment of W and W-based alloys as candidates for plasma facing components.

DOI

http://dx.doi.org/10.1088/0029-5515/54/4/042004

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14_NuclFusion_54,042004_Terentyev.pdf

Atomistic modelling of interaction of edge dislocations with radiation defects in austenitic alloys FeNiCr

alex — Tue, 19 Aug 2014 12:38:12 +0000

A. Bakaev, D. Terentyev, P. Grigorev, E. Zhurkin

ISBN/ISSN:

Talk

Conference / event / venue

XXXXIII Tulinov conference. Physics of interaction of charged particles with crystals

Moscow, Russia

Tuesday, 28 May, 2013 to Thursday, 30 May, 2013

Interaction of moving dislocations with perfect dislocation loops in austenitic alloys FeNiCr

alex — Tue, 19 Aug 2014 12:31:06 +0000

A. Bakaev, D. Terentyev, P. Grigorev, E. Zhurkin

ISBN/ISSN:

Poster

Conference / event / venue

XLIV Tulinov conference. Physics of interaction of charged particles with crystals

Moscow, Russia

Tuesday, 27 May, 2014 to Thursday, 29 May, 2014

Ab initio modeling of fusion reactor materials: Unravelling the hydrogen retention mechanisms

alex — Tue, 19 Aug 2014 12:27:38 +0000

A. Bakaev, P. Grigorev, V. Dubinko, D. Terentyev, W. Van Renterghem, G. Van Oost

ISBN/ISSN:

Poster

Conference / event / venue

International Conference on Scientific Computing 2013

Paphos, Cyprus

Tuesday, 3 December, 2013 to Friday, 6 December, 2013

Trapping of H on dislocations and grain boundaries in W alloys: an atomistic study

alex — Tue, 19 Aug 2014 12:22:32 +0000

A. Bakaev, P. Grigorev, V. Dubinko, D. Terentyev, W. Van Renterghem, G. Van Oost

ISBN/ISSN:

Poster

Conference / event / venue

14th International Conference on Plasma-Facing Materials and Components for Fusion Applications

Julich, Germany

Monday, 13 May, 2013 to Friday, 17 May, 2013