Distinct magnetic states of metastable fcc structured Fe and Fe–Cu alloys studied by ab initio calculations

Kong, Lingti; Liu, B.X.

doi:10.1016/j.jallcom.2005.07.032

Cited by 27 publications

(18 citation statements)

References 40 publications

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“…As mentioned previously, we initialized four different magnetic states which have been tested in two different SQSs (SQSa and SQSb). As already found in previous works for γ -Fe, [13][14][15][16][17] we found many minima very close in energy corresponding to different magnetic states as can be seen in Fig. 1.…”

Section: Reference State Calculationssupporting

confidence: 88%

“…These experiments have shown that γ -Fe displays a noncollinear, spiral magnetic structure. 11,12 The numerous first-principles studies carried out to search for the γ -Fe ground state [13][14][15][16][17][18][19][20] showed many competing magnetic structures lying between 0.08 and 0.15 eV/atom above the bcc ferromagnetic ground state, thus complicating the choice of a relevant reference state for calculations of physical properties in γ -Fe. Another critical issue is to model the PM state in γ -Fe since austenitic SS are PM at temperatures where nuclear reactors operate.…”

Section: Introductionmentioning

confidence: 99%

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First-principles study of point defects in an fcc Fe-10Ni-20Cr model alloy

Piochaud¹,

Klaver²,

Adjanor³

et al. 2014

Phys. Rev. B

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The influence of the local environment on vacancy and self-interstitial formation energies has been investigated in a face-centered-cubic (fcc) Fe-10Ni-20Cr model alloy by analyzing an extensive set of first-principle calculations based on density functional theory. Chemical disorder has been considered by designing special quasirandom structures and four different collinear magnetic structures have been investigated in order to determine a relevant reference state to perform point defect calculations at 0 K. Two different convergence methods have also been used to characterize the importance of the method on the results. Although our fcc Fe-10Ni-20Cr would be better represented in terms of applications by the paramagnetic state, we found that the antiferromagnetic single-layer magnetic structure was the most stable at 0 K and we chose it as a reference state to determine the point defect properties. Point defects have been introduced in this reference state, i.e., vacancies and Fe-Fe, Fe-Ni, Fe-Cr, Cr-Cr, Ni-Ni, and Ni-Cr dumbbell interstitials oriented either parallel or perpendicular to the single layer antiferromagnetic planes. Each point defect studied was introduced at different lattice sites to consider a sufficient variety of local environments and analyze its influence on the formation energy values. We have estimated the point defect formation energies with linear regressions using variables which describe the local environment surrounding the point defects. The number and the position of Ni and Cr first nearest neighbors to the point defects were found to drive the evolution of the formation energies. In particular, Ni is found to decrease and Cr to increase the vacancy formation energy of the model alloy, while the opposite trends are found for the dumbbell interstitials. This study suggested that, to a first approximation, the first nearest atoms to point defects can provide reliable estimates of point defect formation energies.

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Section: Reference State Calculationssupporting

confidence: 88%

Section: Introductionmentioning

confidence: 99%

First-principles study of point defects in an fcc Fe-10Ni-20Cr model alloy

Piochaud¹,

Klaver²,

Adjanor³

et al. 2014

Phys. Rev. B

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“…First-principles studies of γ -Fe with collinear [18][19][20][21][22] and noncollinear 4,23 magnetism have found many distinct magnetically ordered and spin spiral (meta-)stable states lying (approximately) between 0.08 and 0.15 eV/atom above the bcc ferromagnetic ground state, α-Fe. However, techniques allowing reliable first-principles calculations of the paramagnetic state of γ -Fe are only just beginning to appear in the literature, for example, the work of Körmann et al and references therein.…”

Section: Introductionmentioning

confidence: 99%

Defect and solute properties in dilute Fe-Cr-Ni austenitic alloys from first principles

2012

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We present results of an extensive set of first-principles density functional theory calculations of point defect formation, binding, and clustering energies in austenitic Fe with dilute concentrations of Cr and Ni solutes. A large number of possible collinear magnetic structures were investigated as appropriate reference states for austenite. We found that the antiferromagnetic single-and double-layer structures with tetragonal relaxation of the unit cell were the most suitable reference states and highlighted the inherent instabilities in the ferromagnetic states. Test calculations for the presence and influence of noncollinear magnetism were performed but proved mostly negative. We calculate the vacancy formation energy to be between 1.8 and 1.95 eV. Vacancy cluster binding was initially weak at 0.1 eV for divacancies but rapidly increased with additional vacancies. Clusters of up to six vacancies were studied and a highly stable octahedral cluster and stacking fault tetrahedron were found with total binding energies of 2.5 and 2.3 eV, respectively. The 100 dumbbell was found to be the most stable self-interstitial with a formation energy of between 3.2 and 3.6 eV and was found to form strongly bound clusters, consistent with other fcc metals. Pair interaction models were found to be capable of capturing the trends in the defect cluster binding energy data. Solute-solute interactions were found to be weak in general, with a maximal positive binding of 0.1 eV found for Ni-Ni pairs and maximum repulsion found for Cr-Cr pairs of −0.1 eV. Solute cluster binding was found to be consistent with a pair interaction model, with Ni-rich clusters being the most stable. Solute-defect interactions were consistent with Ni and Cr being modestly oversized and undersized solutes, respectively, which is exactly opposite to the experimentally derived size factors for Ni and Cr solutes in type 316 stainless steel and in the pure materials. Ni was found to bind to the vacancy and to the 100 dumbbell in the tensile site by 0.1 eV and was repelled from mixed and compressive sites. In contrast, Cr showed a preferential binding to interstitials. Calculation of tracer diffusion coefficients found that Ni diffuses significantly more slowly than both Cr and Fe, which is consistent with the standard mechanism used to explain radiation-induced segregation effects in Fe-Cr-Ni austenitic alloys by vacancy-mediated diffusion. Comparison of our results with those for bcc Fe showed strong similarity for pure Fe and no correlation with dilute Ni and Cr.

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“…Theoretical studies suggest that the magnetic property of metastable fcc-Fe crystal varies in a wide range from non-magnetic to high-spin ferromagnetic state depending on the distance between atoms. 3,4 Thin fcc-Fe films have been prepared through hetero-epitaxial growth on fcc-Cu underlayers of (100) and (111) orientations. [5][6][7][8][9][10][11] However, the metastable structure tends to transform into more stable bcc structure with increasing the thickness.…”

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confidence: 99%

Metastable fcc-Fe film epitaxially grown on Cu(100) single-crystal underlayer

Ohtake

Shimamoto

Futamoto

2013

Journal of Applied Physics

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Fe film of 40 nm thickness is prepared on fcc-Cu(100) single-crystal underlayer at room temperature by ultra-high vacuum molecular beam epitaxy. The film growth and the detailed structure are investigated by reflection high-energy electron diffraction, cross-sectional high-resolution transmission electron microscopy (HR-TEM), and x-ray diffraction (XRD). An Fe single-crystal with metastable fcc structure nucleates on the underlayer. The HR-TEM shows that fcc lattice is formed from the Fe/Cu interface up to the film surface. A large number of misfit dislocations are introduced around the Fe/Cu interface due to an accommodation of lattice mismatch. Dislocations exist up to the film near surface. The lattice constant is estimated by XRD to be a = 0.3607 nm. The film shows a ferromagnetic property, which reflects the property of fcc-Fe crystal with high-spin ferromagnetic state.

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Distinct magnetic states of metastable fcc structured Fe and Fe–Cu alloys studied by ab initio calculations

Cited by 27 publications

References 40 publications

First-principles study of point defects in an fcc Fe-10Ni-20Cr model alloy

First-principles study of point defects in an fcc Fe-10Ni-20Cr model alloy

Defect and solute properties in dilute Fe-Cr-Ni austenitic alloys from first principles

Metastable fcc-Fe film epitaxially grown on Cu(100) single-crystal underlayer

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