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The ternary rare-earth-metal nickel indides RE23Ni7In4 (RE = Gd, Tb, Dy) were prepared by arc-melting mixtures of the elements followed by annealing at 870 K. They adopt the Yb23Cu7Mg4-type structure (space group P63/mmc, Pearson symbol hP68, Z = 2), as determined by laboratory and synchrotron powder diffraction methods for RE = Gd (a = 9.6435(10) A, c = 22.118(3) A) and Tb (a = 9.5695(8) A, c = 21.983(3) A), and single-crystal X-ray diffraction methods for RE = Dy (a = 9.533(5) A, c = 21.890(13) A). The centrosymmetric Yb23Cu7Mg4-type structure is closely related to the noncentrosymmetric Pr23Ir7Mg4-type structure. Triangular In3 clusters within RE23Ni7In4 represent a rare type of cluster found among metal-rich indides; the reasons for their formation were investigated by density functional theory methods.

The rare-earth germanium sulfide iodides RE3Ge2S8I (RE = La, Ce, Pr) have been prepared by reaction of the elements at 900 °C. They adopt the monoclinic La3(SiO4)2Cl-type structure (space group C2/c, Z = 4; a = 16.156(4)–15.9760(9) A, b = 7.9776(18)–7.8786(5) A, c = 11.081(3)–10.9281(6) A, β = 98.192(5)–98.4525(10)° on progressing from La to Pr for the RE component) consisting of isolated thiogermanate tetrahedral groups [GeS4]4– separated by RE3+ and I− ions. The optical band gaps fall in the range of 2.7–3.1 eV. Magnetic measurements indicated simple paramagnetic behaviour for Ce3Ge2S8I and Pr3Ge2S8I.

A total of 73 new quaternary rare-earth germanides RE4 M2 XGe4 ( RE = rare-earth metal; M = Mn-Ni; X = Ag, Cd) were prepared through reactions of the elements. The solid solution Nd4Mn2Cd(Ge1- ySi y)4 was also prepared under the same conditions and found to be complete over the entire range. All of these compounds adopt the monoclinic Ho4Ni2InGe4-type structure (space group C2/ m, a = 14.2-16.7 A, b = 4.0-4.6 A, c = 6.8-7.5 A, β = 106-109°), as revealed by powder X-ray diffraction analysis and single-crystal X-ray diffraction analysis on selected members. The structure determination of Nd4(Mn0.78(1)Ag0.22(1))2Ag0.83(1)Ge4 disclosed disorder of Mn and Ag atoms within the tetrahedral site and Ag deficiencies within the square planar site. Within the solid solution Nd4Mn2Cd(Ge1- ySi y)4, the end-members and two intermediate members were structurally characterized; as the Si content increases, the Cd sites become less deficient and the individual [Mn2 Tt2] layers contract but become further apart from each other. Electronic band structure calculations confirm that the Ag-Ge or Cd-Ge bonds are the weakest in the structure and thus prone to distortion. Thermal property measurements confirm expectations from machine-learning predictions that these quaternary germanides should exhibit low thermal conductivity, which was found to be

During a systematic search of the RE-Au-Sn (RE = La, Ce, Pr, Nd) ternary phase space, a series of compounds with the general formula REAu1.5Sn0.5 have been identified. These phases can be synthesized by arc melting the elemental metals, followed by annealing. The crystal structures were solved using single-crystal X-ray diffraction, with the composition confirmed by energy-dispersive X-ray spectroscopy. All four compounds crystallize in orthorhombic space group Imma with the CeCu2-type structure. Most notable in these compounds is the polyanionic backbone composed of a single statistically mixed Au/Sn position, which creates a puckered hexagonal bonding network separated by the rare-earth atoms. Electronic structure calculations indicate that the Au 5d bands are dominant in the density of states, while the crystal orbital Hamilton population (-COHP) curves demonstrate Au-Au and Au-Sn interactions, which stabilize the crystal structure. Likewise, a qualitative electron localization function analysis supports the existence of a polyanionic network, and a Bader charge analysis implies anionic character on Au and Sn. The preference for these compounds to adopt the simple CeCu2-type structure is also determined using density functional theory calculations and compared to related compounds to establish a better picture of the unusual behavior of Au in polar intermetallic compounds.

There remain 21 systems (out of over 3500 possible combinations of the elements) in which the existence of the simple binary equiatomic phases AB has not been established experimentally. Among these, the presumed binary phase HfIn is predicted to adopt the tetragonal CuAu-type structure (space group P4/mmm) by a recently developed machine-learning model and by structure optimization through global energy minimization. To test this prediction, the Hf−In system was investigated experimentally by reacting the elements in a 1:1 stoichiometry at 1070 K. Under the conditions investigated, the bulk and surface of the sample correspond to different crystalline phases but have nearly the same equiatomic composition, as revealed by energy-dispersive X-ray analysis. The structure of the bulk sample, which was solved from powder X-ray diffraction data through simulated annealing, corresponds to the γ-brass (Cu5Zn8) type (space group I43m) with Hf and In atoms disordered over four sites. The structure of crystals sel...

The germanides Ce3Rh11Ge5, Ce6Rh30Ge19.5, and CeRh3Ge2, which are new ternary Rh-rich phases in the Ce–Rh−Ge system, were prepared by reactions of the elements. Their crystal structures were determined by single-crystal and powder X-ray diffraction methods. Ce3Rh11Ge5 adopts the Gd3Ru4Al12-type structure, which represents the fully stoichiometric version of the defect Sc3Ni11Ge4-type structure, in hexagonal space group P63/mmc with Z ​= ​2 and cell parameters a ​= ​8.6964 (12) A and c ​= ​9.2209 (12) A. Ce6Rh30Ge19.5 is a filled derivative of the U6Co30Si19-type structure in hexagonal space group P63/m with Z ​= ​2 and cell parameters a ​= ​22.8480 (11) A and c ​= ​3.9208 (2) A. CeRh3Ge2 is derived from a symmetry-lowered distortion of the hexagonal CeCo3B2-type (or substitutionally ordered CaCu5-type) structure, and crystallizes in orthorhombic space group Fmmm with Z ​= ​16 and cell parameters a ​= ​7.392 (6) A, b ​= ​11.341 (9) A, and c ​= ​19.66 (2) A. As expected by their Rh-rich compositions, the three compounds exhibit extensive Rh–Rh bonding, but surprisingly, they also show some short Ge–Ge contacts. Analysis of the electron localization functions and Bader charges reveals that charge transfer takes place from Ce to Rh atoms, indicative of a polar character in the bonding in these intermetallic compounds.

The site preferences within the structures of half-Heusler compounds have been evaluated through a machine-learning approach. A support-vector machine algorithm was applied to develop a model which was trained on 179 experimentally reported structures and 23 descriptors based solely on the chemical composition. The model gave excellent performance, with sensitivity of 93%, selectivity of 96%, and accuracy of 95%. As an illustration of data sanitization, two compounds (GdPtSb, HoPdBi) flagged by the model to have potentially incorrect site assignments were resynthesized and structurally characterized. The predictions of the correct site assignments from the machine-learning model were confirmed by single-crystal and powder X-ray diffraction analysis. These site assignments also corresponded to the lowest total energy configurations as revealed from first-principles calculations.

The Li-containing intermetallic compounds LiCu2Al and LiCu2Ga were prepared by induction heating. Powder X-ray diffraction revealed cubic structures for these compounds: Li0·5CuAl0.5, CsCl-type ( P m 3 ¯ m , Z ​= ​1, a ​= ​2.9283 (2) A); LiCu2Ga, Heusler or Cu2MnAl-type ( F m 3 ¯ m , Z ​= ​4, a ​= ​5.8617 (4) A). Solid-state 7Li NMR spectra confirmed that the Li atoms are situated on a single site rather than being disordered over multiple sites. Optical reflectance spectra show absorption edges in the visible region consistent with the appearance of colour in these compounds: red for LiCu2Al, yellow for LiCu2Ga. Band structure calculations revealed the presence of completely filled Cu 3d states, and suggest that interband transitions from the top of this narrow band (located around 2.5 ​eV below the Fermi level) to empty bands are responsible for the colour.

Solid-state phase equilibria have been established in the Ta–Cr–P system in the region of 0–67 at% P at 1070 K through powder X-ray diffraction analysis. Mutual substitution of Ta and Cr in binary phosphides gives rise to significant homogeneity ranges in Ta 1.00–0.66 Cr 0–0.34 P (NbAs-type; a =3.332(3)–3.1366(3) A, c =11.386(4)–11.364(2) A), Ta 3.0–2.1 Cr 0–0.9 P (Ti 3 P-type, a =10.156(2)–9.9992(2) A, c =5.015(1)–4.956(2) A), and Cr 3.0–2.4 Ta 0–0.6 P (Ni 3 P-type, a =9.186(5)–9.217(4) A, c =4.557(3)–4.5911(3) A). A limited homogeneity range is found in the ternary phase Ta 1.0–0.8 Cr 1.0–1.2 P (TiNiSi-type, a =6.2344(5)–6.141(2) A, b =3.5034(3)–3.3769(6) A, c =7.3769(6)–7.357(2) A). The OsGe 2 -type structures (space group C 2/ m ) of a new P-rich compound, Ta 0.92(2) Cr 0.08(2) P 2 ( a =8.8586(3) A, b =3.2670(2) A, c =7.4871(2) A, β =119.315(2)°) as well as of the Ti-containing analogue Ta 0.93(3) Ti 0.07(3) P 2 ( a =8.8592(5) A, b =3.2663(3) A, c =7.4870(5) A, β =119.309(2)°) were refined from powder X-ray diffraction data.

Six series of quaternary rare-earth transition-metal chalcogenides RE3MGaCh7 (M=Fe, Co, Ni; Ch=S, Se), comprising 33 compounds in total, have been prepared by reactions of the elements at 1050 °C (for the sulphides) or 900 °C (for the selenides). They adopt noncentrosymmetric hexagonal structures (ordered Ce3Al1.67S7-type, space group P63, Z=2) with cell parameters in the ranges of a=9.5–10.2 A and c=6.0–6.1 A for the sulphides and a=10.0–10.5 A and c=6.3–6.4 A for the selenides as refined from powder X-ray diffraction data. Single-crystal structures were determined for five members of the sulphide series RE3FeGaS7 (RE=La, Pr, Tb) and RE3CoGaS7 (RE=La, Tb). The highly anisotropic crystal structures consist of one-dimensional chains of M-centred face-sharing octahedra and stacks of Ga-centred tetrahedra all pointing in the same direction. Magnetic measurements on the sulphides reveal paramagnetic behaviour in some cases and long-range antiferromagnetic behaviour with low Neel temperatures (15 K or lower) in others. Ga L-edge XANES spectra support the presence of highly cationic Ga tetrahedral centres with a tendency towards more covalent Ga–Ch character on proceeding from the sulphides to the selenides. Band structure calculations on La3FeGaS7 indicate that the electronic structure is dominated by Fe 3d-based states near the Fermi level.

The four series of quaternary sulfides RE3Zn0.5SiS7 (RE = La–Nd, Sm, Gd–Er), RE3Zn0.5GeS7 (RE = La–Nd, Sm, Gd–Er), RE3Cd0.5SiS7 (RE = La–Nd, Sm, Gd–Ho), and RE3Cd0.5GeS7 (RE = La–Nd, Sm, Gd, Tb) were prepared by reactions of the elements at 1050 °C. Analysis of their powder X-ray diffraction patterns indicates that they adopt the noncentrosymmetric hexagonal La3Mn0.5SiS7-type structure (space group P63, Z = 2). The structures of two Cd-containing members were refined from single-crystal X-ray diffraction data (Gd3Cd0.5SiS7, a = 9.9737(8) A, c = 5.6287(4) A; Gd3Cd0.5GeS7, a = 9.9739(3) A, c = 5.7296(4) A). La3Zn0.5GeS7 melts incongruently above 1300 °C. Ce3Zn0.5GeS7 shows simple paramagnetic behaviour arising from non-interacting Ce3+ species. Optical band gaps of 2.7 eV for La3Cd0.5SiS7, 2.3 eV for La3Cd0.5GeS7, and 1.8 eV for Ce3Zn0.5GeS7 were measured. Band structure calculations on La3Cd0.5SiS7 and La3Cd0.5GeS7 confirm the presence of band gaps whose magnitude is controlled by Si–S or Ge–S bonding interactions.

Reactions of the elements through arc-melting and annealing at 800 °C have led to the ternary rare-earth manganese germanides RE2+xMnGe2+y (RE=La, Ce). The approximate composition is RE2.1MnGe2.2, as determined by single-crystal X-ray diffraction studies on the La member (space group P4/nmm, a=16.0491(4) A, c=8.1587(2) A, Z=16). Although this composition is close to other germanides RE2MGe2 (Sc2CoSi2-type), the structure is completely unrelated. Rather, La2.1MnGe2.2 contains layers built up of Mn-centred tetrahedra in two types of arrangements, four-membered rings and stellae quadrangulae, with La and additional Ge atoms in the intervening spaces. Disorder of La atoms, isolated Ge atoms, and Ge2 dimers takes place within tunnels in the structure. Electrical and magnetic measurements on La2.1MnGe2.2 indicate metallic behaviour and likely ferromagnetic ordering with a transition temperature above 300 K.

Abstract Phase equilibria was investigated in the Ti-Fe-P system at T = 1070 K in the region 0–67 at.% of P, employing X-ray powder diffraction. The two ternary compounds, namely Ti0.5–0.8Fe1.5−1.2P (Co2Si-type; space group Pnma; a = 0.5964(2)–0.6011(3), b = 0.3575(3)–0.3600(1), c = 0.6828(2)–0.6882(2) nm) and Ti0.85−1.25Fe1.15−0.75P (ZrNiAl-type; space group P-62m; a = 0.6071(4)–0.6117(1), c = 0.3510(9)–0.3506(1) nm) exist in the Ti-Fe-P system at this temperature. The crystal structure of the Ti0.85–1.25Fe1.15−0.75P compound was additionally determined by X-ray single crystal diffraction on the phase with stoichiometric composition. The substitutions of Ti by Fe were observed for Ti5P3.16, Ti3P and TiP phases, and Fe for Ti in the case of Fe3P, Fe2P binary compounds. Graphical abstract

Through arc-melting reactions of the elements and annealing at 800 °C, the ternary rare-earth germanides RE 3 Ru 2 Ge 3 and RE 3 Ir 2 Ge 3 have been prepared for most of the smaller RE components ( RE =Y, Gd–Tm, Lu). In the iridium-containing reactions, the new phases RE 2 IrGe 2 were also generally formed as by-products. Powder X-ray diffraction revealed orthorhombic Hf 3 Ni 2 Si 3 -type structures (space group Cmcm , Z =4) for RE 3 M 2 Ge 3 ( M =Ru, Ir) and monoclinic Sc 2 CoSi 2 -type structures (space group C 2/ m , Z =4) for RE 2 IrGe 2 . Full crystal structures were determined by single-crystal X-ray diffraction for all members of RE 3 Ru 2 Ge 3 ( a =4.2477(6) A, b =10.7672(16) A, c =13.894(2) A for RE =Y; a =4.2610(3)–4.2045(8) A, b =10.9103(8)–10.561(2) A, c =14.0263(10)–13.639(3) A in the progression of RE from Gd to Lu) and for Tb 3 Ir 2 Ge 3 ( a =4.2937(3) A, b =10.4868(7) A, c =14.2373(10) A). Both structures can be described in terms of CrB- and ThCr 2 Si 2 -type slabs built from Ge-centred trigonal prisms. However, band structure calculations on Y 3 Ru 2 Ge 3 support an alternative description for RE 3 M 2 Ge 3 based on [ M 2 Ge 3 ] layers built from linked M Ge 4 tetrahedra, which emphasizes the strong M –Ge covalent bonds present. The temperature dependence of the electrical resistivity of RE 3 Ru 2 Ge 3 generally indicates metallic behaviour but with low-temperature transitions visible for some members ( RE =Gd, Tb, Dy) that are probably associated with magnetic ordering of the RE atoms. Anomalously, Y 3 Ru 2 Ge 3 exhibits semiconductor-like behaviour of uncertain origin. Magnetic measurements on Dy 3 Ru 2 Ge 3 reveal antiferromagnetic ordering at 3 K and several unusual field-dependent transitions suggestive of complex spin reorientation processes.

Construction of the isothermal section in the metal-rich portion (67 atom % P) of the Mo-Fe-P phase diagram at 800 °C has led to the identification of two new ternary phases: (Mo(1-x)Fe(x))(2)P (x = 0.30-0.82) and (Mo(1-x)Fe(x))(3)P (x = 0.10-0.15). The occurrence of a Co(2)Si-type ternary phase (Mo(1-x)Fe(x))(2)P, which straddles the equiatomic composition MoFeP, is common to other ternary transition-metal phosphide systems. However, the ternary phase (Mo(1-x)Fe(x))(3)P is unusual because it is distinct from the binary phase Mo(3)P, notwithstanding their similar compositions and structures. The relationship has been clarified through single-crystal X-ray diffraction studies on Mo(3)P (α-V(3)S-type, space group I42m, a = 9.7925(11) Å, c = 4.8246(6) Å) and (Mo(0.85)Fe(0.15))(3)P (Ni(3)P-type, space group I4, a = 9.6982(8) Å, c = 4.7590(4) Å) at -100 °C. Representation in terms of nets containing fused triangles provides a pathway to transform these closely related structures through twisting. Band structure calculations support the adoption of these structure types and the site preference of Fe atoms. Electrical resistivity measurements on (Mo(0.85)Fe(0.15))(3)P reveal metallic behavior but no superconducting transition.

The interaction between components in the Zr–Ti–P system in the range of up to 67 at.% P was analyzed and the isothermal section diagram at 1070 K was constructed from X-ray structural and EDS analysis. Solid substitutional solutions based on the binary phosphides M 3 P with the Ti 3 P-type structure (Ti 3.0−2.3 Zr 0−0.7 P and Zr 3.0−2.5 Ti 0−0.5 P) were found. The phosphide (Ti,Zr) 2 P with the Co 2 Si-type structure is homogeneous at the Zr 1.2−0.6 Ti 0.8−1.4 P composition. From powder X-ray diffraction methods, the crystal structure of ZrTiP 0.68 was shown to be of the Zn 3 Cu-type (space group P -6, a = 0.47600(1), c = 0.30038(1) nm, R I = 0.0444); HfTiP 0.68 is isostructural. These compounds are homogenous in the range Zr 1.0−1.5 Ti 1.0−0.5 P 0.68 and Hf 0.9−1.2 Ti 1.1−0.8 P 0.68 . From single-crystal methods, the structure of Zr 0.93 Ti 0.07 P 0.93 was determined to belong to the WC-type structure (space group P -6 m 2, a = 0.3004(2), c = 0.3117(3) nm, R F = 0.0228).

Attempts to prepare Gd12Co5Bi, a member of the rare-earth (RE) intermetallics RE12Co5Bi, which were identified by a machine-learning recommendation engine as potential candidates for thermoelectric materials, led instead to formation of the new compound Gd12Co5.3Bi with a very similar composition. Phase equilibria near the Gd-rich corner of the Gd-Co-Bi phase diagram were elucidated by both lab-based and variable-temperature synchrotron powder X-ray diffraction, suggesting that Gd12Co5.3Bi and Gd12Co5Bi are distinct phases. The higher symmetry structure of Gd12Co5.3Bi (cubic, space group Im3̅, Z = 2, a = 9.713(6) Å), as determined from single-crystal X-ray diffraction, is closely related to that of Gd12Co5Bi (tetragonal, space group Immm). Single Co atoms and Co-Co dumbbells are disordered with occupancies of 0.78(2) and 0.22(2), respectively, in Gd12Co5.3Bi, but they are ordered in Gd12Co5Bi. Consistent with this disorder, the electrical resistivity shows less dependence on temperature for Gd12Co5.3Bi than for Gd12Co5Bi. The thermal conductivity is low and reaches 2.8 W m(-1) K(-1) at 600 °C for both compounds; however, the temperature dependence of the thermal conductivity differs, decreasing for Gd12Co5.3Bi and increasing for Gd12Co5Bi as the temperature increases. The unusual trends in thermal properties persist in the heat capacity, which decreases below 2R, and in the thermal diffusivity, which increases at higher temperatures.

Phase equilibria in the Hf–Ti–P system were investigated at T = 1070 K in the region 0–67 at.% of P, employing X-ray powder diffraction. The three ternary compounds exist in the Hf–Ti–P system at this temperature. Two of them have homogeneity regions and their compositions can be represented as Hf x Ti 2− x P (0.65 ⩽ x ⩽ 1.30; TiNiSi-type, space group Pnma , a = 6.130(3)–6.673(5), b = 3.508(2)–3.557(2), c = 8.050(5)–8.161(2) A) and Hf x Ti 2− x P 0.68 . (0.75 ⩽ x ⩽ 1.00; Zn 3 Cu-type, space group Р -6, a = 4.758(1)–4.803(1), c = 3.005(1)–3.035(1) A). The crystal structure of the new phosphide Hf 5.35 Ti 8.65 P 8.93 was determined by X-ray single crystal diffraction. This compound crystallizes with the Zr 14 P 9 -type structure (space group Pnnm , cell parameters a = 15.973(1), b = 26.335(2), c = 3.5281(2) A, R 1 = 0.0670; wR 2 = 0.0875). The majority of binary compounds form substitution type solid solutions, in their homogeneity ranges the substitution of Ti by Hf or Hf for Ti takes place.

Arc-melting and annealing of the elements (evacuated silica tubes, 800 °C, 1 week) is used to prepare ≈50 new quaternary germanides of the series Ln4M2InGe4 (Ln: Ce—Lu except Eu and Yb; M: Fe, Co, Ni, Ru, Rh, Ir) and a different but closely related series Ln4RhInGe4.

The formation of quaternary rare-earth (RE) germanides containing transition metals (M's) from groups 6 to 10 was investigated through arc-melting and annealing reactions at 800 °C; about 50 new compounds were obtained. These include several new series of quaternary germanides RE4M2InGe4 (M = Fe, Co, Ru, Rh, Ir), previously known only for M = Mn and Ni; additional members of RE4Ni2InGe4 extended to other RE substituents; and a different but closely related series RE4RhInGe4. Detailed crystal structures were determined by single-crystal X-ray diffraction studies for 20 compounds. Monoclinic structures in space group C2/m are adopted by RE4M2InGe4 (Ho4Ni2InGe4-type, a = 15.1-16.5 A, b = 4.1-4.4 A, c = 6.9-7.3 A, β = 106.2-108.6°) and RE4RhInGe4 (own type, a = 20.0-20.2 A, b = 4.2-4.3 A, c = 10.1-10.2 A, β = 105.0-105.3°). Both structures contain frameworks built from MGe4 tetrahedra, InGe4 square planes, and Ge2 dimers, delimiting tunnels occupied by RE atoms. These structures can also be derived by cutting slabs along different directions from the more symmetrical RE2InGe2 structure. Although the Ge2 dimers are relatively invariant, the InGe4 square planes can undergo distortion to form two sets of short versus long In-Ge distances. This distortion results from a competition between M-Ge bonding in the MGe4 tetrahedra and In-Ge bonding in the InGe4 square planes.

The new title compounds (RE: Y, La—Er) are prepared from stoichiometric mixtures of the elements at 1050 °C (14 d) for the sulfides and at 900 °C (5 d) for the selenides, respectively.

La2+xMnGe2+y (I) and Ce2+xMnGe2+y (II) are prepared by arc-melting of the elements in molar ratios of 2:1:2 followed by annealing (sealed silica tubes, 800 °C, 2 weeks).

The quaternary germanides RE4Mn2InGe4 (RE = La-Nd, Sm, Gd-Tm, Lu) have been prepared by arc-melting reactions of the elements and annealing at 800 °C and represent the second example of the RE4M2InGe4 series previously known only for M = Ni. Single-crystal X-ray diffraction studies conducted on the earlier RE members of RE4Mn2InGe4 confirmed that they adopt the monoclinic Ho4Ni2InGe4-type structure [space group C2/m, a = 16.646(2)-15.9808(9) Å, b = 4.4190(6)-4.2363(2) Å, c = 7.4834(10)-7.1590(4) Å, β = 106.893(2)-106.304(1)° in the progression of RE from La to Gd]. The covalent framework contains Mn-centered tetrahedra and Ge2 dimers that build up [Mn2Ge4] layers, which are held weakly together by four-coordinate In atoms and outline tunnels filled by the RE atoms. This bonding picture is supported by band-structure calculations. An alternative description based on Ge-centered trigonal prisms reveals that RE4Mn2InGe4 is closely related to RE2InGe2. The electrical resistivity behavior of Pr4Mn2InGe4 is similar to that of Pr2InGe2.

Two new ternary phases, (Mo1-xFex)2P (x = 0.30—0.82) and (Mo1-xFex)3P (x = 0.10—0.15) exist in the isothermal section of the title system at 800 °C.