Release Time:2019-03-11  Hits:

Indexed by: Journal Article

Date of Publication: 2017-10-01

Journal: COMPUTATIONAL MATERIALS SCIENCE

Included Journals: EI、SCIE、Scopus

Volume: 138

Page Number: 267-276

ISSN: 0927-0256

Key Words: Fe-9Cr alloy; Magnetic moment; Helium; Vacancy; Density of states

Abstract: Under the extreme fusion environment, helium impurities and vacancies play an important role in the microstructure evolution in Fe-9Cr based (wt.%) reduced activation ferritic/martensitic (RAFM) steels. In this work, vacancy and helium (He) impurity formation and related magnetism change in Fe-9Cr alloys are investigated by first-principles calculations. In Fe-9Cr alloys, Cr atom has an antiferromagnetic moment of around -1.85 mu g, as compared to that of Fe atoms in matrix. Contrary to the case for the first nearest neighboring (1 nn) and 2 nn Cr atom around Fe atom, 3-5 nn Cr atoms increase the magnetic moment of Fe atom. The formation energy of vacancy and He impurities at various sites in Fe-9Cr are discussed. In Fe-9Cr alloys, He atoms at octahedral interstitial sites (O-sites) are unstable and eventually move to tetrahedral interstitial sites (T-sites) upon relaxation. The formation of defects can strongly affect the magnetic moment. T-site He atom leads to an obvious magnetic moment of 1 nn Cr decrease. The electronic structure and local strain field analyses are performed to understand the origin of energy difference of He at different interstitial sites in Fe-9Cr alloys. The present theoretical results are helpful for a better understanding of the behavior of vacancy, He impurity and their complexes in Fe-9Cr alloys. (C) 2017 Elsevier B.V. All rights reserved.