Cr interactions with He and vacancies in dilute Fe-Cr alloys from first principles

Journal Article · Fri Jul 01 00:00:00 EDT 2011 · Physical Review. B, Condensed Matter and Materials Physics

DOI:https://doi.org/10.1103/PHYSREVB.84.014203· OSTI ID:21596816

Martinez, Enrique; Fu, Chu-Chun ^[1]

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1. Service de Recherches de Metallurgie Physique, CEA/Saclay, F-91191 Gif-sur-Yvette (France)

We have performed density functional theory calculations to study the effect of Cr in the formation of He-vacancy (He{sub n}V{sub m}) clusters in a dilute Fe-Cr system. We find a significant repulsive interaction between Cr and He at neighboring tetrahedral sites. The octahedral He close to Cr becomes unstable falling to a nearby tetrahedral site, unlike in pure systems. We note a slight electronic interaction between an interstitial He and the metal atoms, stronger with Cr and responsible of their repulsion. The effect of a Cr atom in the formation of He{sub n}V{sub m} clusters is small except for cases with high He-to-vacancy (n/m) ratio. In systems with multiple Cr atoms we find that, while interstitial He always repels Cr, a vacancy or a substitutional He may screen the ferromagnetic Cr coupling and promote their clustering around them. Two different behavior regimes may therefore be suggested. When the n/m ratio is close to 1 or lower the Cr atoms seem to be attracted to the He{sub n}V{sub m} cluster while when the n/m ratio is greater than 1 the Cr atoms are in general repelled from it. Concerning diffusion, the energy barrier for a tetrahedral He to hop toward a neighboring position of Cr is found to be twice as large as its migration barrier in pure Fe (0.12 vs 0.06 eV). On the other hand, the diffusion of a substitutional He via the dissociative mechanism has a slightly higher dissociation barrier for first nearest neighbor sites of a Cr atom. For the vacancy mechanism we find similar diffusion properties in dilute Fe-Cr systems and in pure Fe except a slightly lower barrier close to Cr that may induce small trapping effects at low temperatures.

• OSTI ID: 21596816
• Journal Information: Physical Review. B, Condensed Matter and Materials Physics, Vol. 84, Issue 1; Other Information: DOI: 10.1103/PhysRevB.84.014203; (c) 2011 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 1098-0121
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
36 MATERIALS SCIENCE
ATOMS
BINARY ALLOY SYSTEMS
CHROMIUM ALLOYS
COMPUTERIZED SIMULATION
COUPLING
DENSITY FUNCTIONAL METHOD
DIFFUSION
DISSOCIATION
HELIUM
INCLUSIONS
INTERACTIONS
INTERSTITIALS
IRON ALLOYS
METALS
MIGRATION
TRAPPING
VACANCIES
ALLOY SYSTEMS
ALLOYS
CALCULATION METHODS
CRYSTAL DEFECTS
CRYSTAL STRUCTURE
ELEMENTS
FLUIDS
GASES
NONMETALS
POINT DEFECTS
RARE GASES
SIMULATION
TRANSITION ELEMENT ALLOYS
VARIATIONAL METHODS