Exploration of new superconductors and functional materials, and fabrication of superconducting tapes and wires of iron pnictides

Predicting and characterizing the crystal structure of materials is a key problem in materials research and development. We report the results of ab initio LDA/GGA computations for the following systems: AgAu, AgCd, AgMg, AgMo∗, AgNa, AgNb∗, AgPd, AgRh∗, AgRu∗, AgTc∗, AgTi, AgY, AgZr, AlSc, AuCd, AuMo∗, AuNb, AuPd, AuPt∗, AuRh∗, AuRu∗, AuSc, AuTc∗, AuTi, AuY, AuZr, CdMo∗, CdNb∗, CdPd, CdPt, CdRh, CdRu∗, CdTc∗, CdTi, CdY, CdZr, CrMg∗, MoNb, MoPd, MoPt, MoRh, MoRu, MoTc∗, MoTi, MoY ∗, MoZr, NbPd, NbPt, NbRh, NbRu, NbTc, NbY ∗, NbZr∗, PdPt, PdRh∗, PdRu∗, PdTc, PdTi, PdY, PdZr, PtRh, PtRu, PtY, PtTc, PtTi, PtZr, RhRu, RhTc, RhTi, RhY, RhZr, RuTi, RuTc, RuY, RuZr, TcTi, TcY, TcZr, TiZr∗, Y Zr∗ (∗= systems in which the ab initio method predicts that no compounds are stable). A detailed comparison to experimental data confirms the high accuracy with which ab initio methods can predict ground states.

Accuracy of ab initio methods in predicting the crystal structures of metals: A review of 80 binary alloys

46 structure types of binary and ternary intermetallic compounds have been derived from the well known, simple aristotype AlB 2 . Many compounds with the general compositions RX 2 , RT 2 , R7X, and R 2 TX 3 (R = alkaline earth, rare earth or actinoid metal: T = transition metal; X = main group element) belong to this family. The structural similarities between these compounds are manifested by an ordering of the transition metal atoms and main group element atoms on the boron positions of the AlB 2 type. Also an ordering of vacancies on the boron positions occurs in some compounds. Striking structural motifs of the RX 2 , RT 2 , RTX, and R 2 TX 3 compounds are planar or puckered six-membered rings consisting of X 6 , T 6 . T 3 X 3 , and T 2 X 4 separated by the respective R atoms The crystal chemical relationships between these compounds are discussed on the basis of a group-subgroup scheme in the concise and compact Barnighausen formalism with respect to the aristotype AlB 2 . Two different branches of AlB 2 related structures are discussed. In the first, the hexagonal/trigonal branch, six-membered rings carry at least a three-fold axis, while in the orthorhombic/ monoclinic branch the distortions are more pronounced. The pseudo-hexagons show significant tilting and a loss of hexagonal/trigonal symmetry. Significant variations of the chemical bonding occur for some structure types, and therefore they may only be considered to be isopointal rather than isotypic. These isopointal conversions are based on a gradual changeover from two- to three-dimensionally infinite polyanions. Besides the group theoretical group-subgroup scheme we also discuss chemical bonding in these AlB 2 related intermetallic compounds.

AlB2-related intermetallic compounds – a comprehensive view based on group-subgroup relations

Predicting and characterizing the crystal structure of materials is a key problem in materials research and development. We report the results of ab initio LDA/GGA computations for the following systems: AgAu, AgCd, AgMg, AgMo*, AgNa, AgNb*, AgPd, AgRh*, AgRu*, AgTc*, AgTi, AgY, AgZr, AlSc, AuCd, AuMo*, AuNb, AuPd, AuPt*, AuRh*, AuRu*, AuSc, AuTc*, AuTi, AuY, AuZr, CdMo*, CdNb*, CdPd, CdPt, CdRh, CdRu*, CdTc*, CdTi, CdY, CdZr, CrMg*, MoNb, MoPd, MoPt, MoRh, MoRu, MoTc*, MoTi, MoY*, MoZr, NbPd, NbPt, NbRh, NbRu, NbTc, NbY*, NbZr*, PdPt, PdRh*, PdRu*, PdTc, PdTi, PdY, PdZr, PtRh, PtRu, PtY, PtTc, PtTi, PtZr, RhRu, RhTc, RhTi, RhY, RhZr, RuTi, RuTc, RuY, RuZr, TcTi, TcY, TcZr, TiZr*, YZr* (*= systems in which the ab initio method predicts that no compounds are stable). A detailed comparison to experimental data confirms the high accuracy with which ab initio methods can predict ground states. 
Keywords: Binary Alloys, Ab initio, Intermetallics, Transition Metals, StructureAluminum, Cadmium, Gold, Magnesium, Molybdenum, Niobium, Palladium, Platinum, Rhodium, Ruthenium, Scandium, Silver, Sodium, Titanium, Technetium, Yttrium, Zirconium.

Accuracy of ab initio methods in predicting the crystal structures of metals: review of 80 binary alloys

Review on magnetic and related properties of RTX compounds

Over 100 new equiatomic ternary rare earth (R)-transition metal (T) silicides, germanides and gallides were synthesized and structurally analysed either by evaluating powder diffraction photographs or in the case of ScRhSi, ScPtSi, YNiSi, ScRuGe and PrPtGe by refining single-crystal diffraction data. The hexagonal ZrNiAl type, an Fe2P-type derivative, was found for ScRuSi and ScTGe (T ≡ Ru, Rh, Pd, Os). The orthorhombic TiNiSi type, a PbCl2-type derivative, was assigned to RRhGa (R ≡ Er, Y), RPdGa (R ≡ La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Lu, Y, Sc), RIrGa (R ≡ Er, Y), RPtGa (R ≡ La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y, Sc), YNiSi, RRhSi (R ≡ Er, Y, Sc), ScPdSi, RIrSi (R ≡ Gd, Er, Y, Sc), RPtSi (R ≡ Tb, Dy, Ho, Er, Tm, Lu, Y, Sc), RRhGe (R ≡ Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Y, Sc), RIrGe (R ≡ Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Y, Sc) and RPtGe (R ≡ Sm, Gd, Tb, Dy, Ho, Er, Tm, Y, Sc). The CeCu2 type, which is related to TiNiSi, was found for R(Pd0.5Ge0.5)2 (R ≡ La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Y) and R(Pt0.5Ge0.5)2 (R ≡ Ce, Pr, Nd) where the palladium or platinum and germanium atoms are arranged at random on the copper sites. The tetragonal LaPtSi type, a ThSi2-type derivative, was found for RPtSi (R ≡ La, Ce, Pr, Nd, Sm, Gd), LaIrGe and LaPtGe. Finally the cubic LaIrSi type, an SrSi2-type derivative, was found for LaIrSi. The occurrence and structural features of these five structure types together with the tetragonal PbFCl type, an Fe2As-type derivative found earlier for RFeSi and RCoSi compounds, are discussed.

Equiatomic ternary rare earth-transition metal silicides, germanides and gallides

http://journals.iucr.org/b/issues/1983/05/00/a22173/a22173.pdf

Ternary BaAl4-type derivative structures

The following structural details were determined for Y 2 Ni 3 Si 5 : M r = 494.37 (orthorhombic); space group, Ibam ; a = 9.5651(4) A ; b = 11.1284(6) A ; c = 5.6453(2) A ; V= 600.91(8) A 3 ; Z = 4; D x = 5.465 Mg m −3 ; Mo Kα, λ = 0.71069 A ; μ (Mo Kα ) = 29.8 mm −1 ; F (000) = 928; T = 293 K . The structure was refined to wR = 0.074 for 422 independent reflections. Ce 2 Co 3 Si 5 , Ce 2 Ni 3 Si 5 and Dy 2 Ni 3 Si 5 have the same crystal structure which is known as the U 2 Co 3 Si 5 type. This structure type can be interpreted as an intergrowth of two kinds of structural slabs, one of which is related to the CaBe 2 Ge 2 structure and the other is related to the BaNiSn 3 structure. The U 2 Co 3 Si 5 and the Sc 2 Fe 3 Si 5 structure types are different stacking variants of identical structural columns.

Ce2Co3Si5 and R2Ni3Si5 (R ≡ Ce, Dy, Y) with the orthorhombic U2Co3Si5-type structure and the structural relationship with the tetragonaL Sc2Fe3Si5-type structure

Lu2Co3Si5 was found to have the following structural characteristics: Mr = 667.2, monoclinic, mC40, C 2 c , a = 10.640(5) A , b = 11.358(5) A , c = 5.432(3) A , β = 118.37(4)°, Z = 4, Dx = 7.67 Mg m−3, μ(MoKα) = 56 mm−1 and F(000) = 1172. Single-crystal X-ray diffraction data were used for the structure refinement. Rw is 0.074 for 796 independent reflections. The crystal structure is a monoclinic deformation variant of the orthorhombic U2Co3S5-type structure. Dy2Co3Si5, Y2Co3Si5 and Sc2Co3Si5 are isotypic with Lu2Co3Si5. Sc2Co3Si5 was previously reported to have the orthorhombic U2Co3Si5-type structure; however, this could not be corroborated.

B. Chabot

Papers

Equiatomic ternary rare earth-transition metal silicides, germanides and gallides

Ternary BaAl4-type derivative structures

Ce2Co3Si5 and R2Ni3Si5 (R ≡ Ce, Dy, Y) with the orthorhombic U2Co3Si5-type structure and the structural relationship with the tetragonaL Sc2Fe3Si5-type structure

Dy2Co3Si5, Lu2Co3Si5, Y2Co3Si5 and Sc2Co3Si5 with a monoclinic structural deformation variant of the orthorhombic U2Co3Si5 structure type

TiMnSi2 and TiFeSi2 with new orthorhombic-type structure