Refinement of an R phase, Mn85.5Si14.5

Shoemaker, C. B.; Shoemaker, David P.

doi:10.1107/s0567740878003908

Cited by 20 publications

(20 citation statements)

References 11 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Moreover, incomplete A filling of site 6c 3 should be considered to be able to describe compositions below 46.2 at.% A like in Mo -Co system. Therefore, the model proposed is (A,B) 3 (A) 12 (A,B) 6 (A,B) 18 .…”

Section: Discussionmentioning

confidence: 99%

“…A m phase was previously reported to exist at the composition 85.7 at.% Mn at the same temperature (600 8C) by Gladyshevskii et al [9] from X-ray diffraction analysis and found to be in equilibrium with the R phase (R3, hR53, Co 5 Cr 2 Mo 3 prototype [18]) on the Mn rich side and with the n phase (Immm, oI186, Mn 4 Si prototype [19]) on the Mn poor side. This phase has not been reported by Wieser and Forgeng [20] in a careful investigation of the phase diagram by X-ray and metallographic analyses, even at this same temperature.…”

Section: Mn -Simentioning

confidence: 94%

See 1 more Smart Citation

Mixed site occupancies in the μ phase

Joubert

Dupin

2004

Intermetallics

View full text Add to dashboard Cite

Section: Discussionmentioning

confidence: 99%

Section: Mn -Simentioning

confidence: 94%

Mixed site occupancies in the μ phase

Joubert

Dupin

2004

Intermetallics

View full text Add to dashboard Cite

“…Note that the crystallographic directions and planes in the R structure are indexed in terms of the hexagonal system, instead of the trigonal one. According to previous studies, 33,36 it has been reported that there are CN12, CN13, and CN16 polyhedra in the ␣-Mn structure consisting of 58 atoms in a unit cell, and CN12, CN14, CN15, and CN16 ones in the R structure of 159 atoms. In spite of the presence of various coordination polyhedra, the notable feature of the ␣-Mn and R structures is that these structures commonly involve penetrated pairs consisting of two CN16 polyhedra.…”

Section: Fig 2 ͑Color͒mentioning

confidence: 89%

“…% Si. 35,36 As a result of the appearance of the R phase, there is a ͑␤-Mn→ ␣-Mn+ R͒ eutectoid reaction that is characterized by structural changes between coordination-polyhedra structures. 37 Although we have so far studied the formation of the coordination-polyhedra structures from the bcc structure in the Fe-Mo and Cr-Co alloy systems, [38][39][40][41][42] the presence of this eutectoid reaction presents us with the following question: "what are the crucial factors controlling a structural change between two coordination-polyhedra structures?"…”

Section: Introductionmentioning

confidence: 99%

Formation ofα-MnandRstructures from theβ-Mnstructure in Mn-Si alloys

et al. 2010

View full text Add to dashboard Cite

The Mn-Si alloy system undergoes the ͑␤-Mn→ ␣-Mn+ R͒ eutectoid reaction at 908 K around 8 at. % Si. The crystal structures of the ␤-Mn, ␣-Mn, and R phases were reported to consist of complex coordination polyhedra such as a polyhedron with coordination number ͑CN͒ 12: that is, an icosahedral atomic cluster. The notable features of these structures are that both the ␣-Mn and R structures are characterized by arrays of penetrated CN16 pairs while penetrated CN14 pairs are present in the ␤-Mn structure. In a penetrated CN16 pair consisting of two CN16 polyhedra, for instance, a center atom of one CN16 polyhedron is one of 16 atoms forming a shell of the other. To understand the crucial factors controlling a change between two coordinationpolyhedra structures, in this study, the crystallographic features of the ͑␤-Mn→ ␣-Mn͒ and ͑␤-Mn→ R͒ structural changes related to the eutectoid reaction have been investigated by transmission electron microscopy. It was found that the former ͑␤-Mn→ ␣-Mn͒ change started with the conversion of a penetrated CN14 pair into a penetrated CN16 pair by successive and simple atomic shifts. Among three types of orientation relations between the ␤-Mn and R structures in the latter change, the direct conversion of a penetrated CN16 pair from a penetrated CN14 pair should first occur for the major relation. As for two other minor relations found mainly for higher Si contents, in the starting changes, a penetrated pair consisting of CN14 and CN12 polyhedra, and two neighboring CN14 and CN12 polyhedra in the ␤-Mn structure must be converted to a penetrated CN16 pair, and two neighboring CN16 and CN12 polyhedra in the R structure, respectively. The directional relation in the orientation relationship for these two structural changes was, as a result, determined by orientations of the penetrated CN14 pairs or two neighboring polyhedra in the ␤-Mn structure. It is thus understood that the crucial factor controlling the ͑␤-Mn→ ␣-Mn͒ and ͑␤-Mn→ R͒ structural changes should be the conversion between the structural units consisting of only two neighboring polyhedra, which are involved in these complex structures. Furthermore, both site occupancies of atoms and atomic-bond lengths in the penetrated CN16 pairs for the ␣-Mn and R structures were evaluated to understand the physical origin of interplay between the appearance of a magnetic moment in the former structure and the formation of covalentlike atomic bonding in the latter.

show abstract

“…8 The feature of the crystal structure of this phase, which is called the R structure, is that 12-, 14-, 15-, and 16-coordination ͑CN͒ polyhedra are involved in the structure, as in the case of the phase. Although structural data for the R structure with rhombohedral symmetry have been established for the Mn-Si and Mo-Co-Cr alloy systems, 9,10 its characteristic features, such as the structural units, are not yet understood. The simple question remains whether these polyhedra can be identified as structural units or not in the R structure.…”

Section: Introductionmentioning

confidence: 99%

Crystal-structure units of theR(Fe3Mo2)phase in the Fe-Mo alloy system

Doi¹,

Tanimura

Koyama³

2008

Phys. Rev. B

View full text Add to dashboard Cite

Around 37 at. % Mo in the Fe-Mo alloy system, in the temperature range between 1473 and 1761 K, there exists the intermetallic-compound R phase, whose crystal structure involves 12-, 14-, 15-, and 16-coordination polyhedra. To determine the crystal-structure units of the R phase, the crystallographic features of the bcc-to-R structural change in the ͑bcc→ bcc+ R͒ reaction of the Fe-Mo system have been investigated by transmission electron microscopy. It was found that atomic columns, which were identified as the secondary structural unit, appeared first in the initial stage of the reaction. Based on this fact, the R phase is understood to have a crystal structure consisting of atomic columns, just as in the case of the structure ͓A. Hirata et al., Phys. Rev. B 74, 054204 ͑2006͔͒. Although only 12-coordination polyhedra form an atomic column in the structure, the column in the R structure consists of two kinds of polyhedra: that is, 16-and 12-coordination ones. Of these two polyhedra, in particular, the appearance of a 16-coordination polyhedron as the primary structural unit of the R structure is associated with the formation of covalent bonds in alloys.

show abstract

Refinement of an R phase, Mn_85.5Si_14.5

Abstract: The structure of the R phase has been refined by full-matrix least squares with diffractometer data from a single-crystal fragment of Mn85.5Si14. 5. The rhombohedral lattice constants are: a = 8.959 (3)

Cited by 20 publications

References 11 publications

Mixed site occupancies in the μ phase

Mixed site occupancies in the μ phase

Formation ofα-MnandRstructures from theβ-Mnstructure in Mn-Si alloys

Crystal-structure units of theR(Fe3Mo2)phase in the Fe-Mo alloy system

Contact Info

Product

Resources

About