Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270103027252/bc1029sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270103027252/bc1029Isup2.hkl |
Samples with U:Co:Al atomic ratios of 1:1:4 were prepared by standard arc-melting techniques. Ingots were placed in alumina crucibles and sealed in fused silica tubes under a residual atmosphere of argon for a heat-treatment at 1173 K for 500 h, or annealed at 1873 K for 10 h using a high-frequency furnace. Single crystals of UCoAl4 could be extracted from crushed as-cast samples. X-ray diffraction powder patterns were collected using monochromatic Cu Kα1 radiation and Co Kα radiation. Scanning electron microscopy and energy dispersive spectroscopy (SEM-EDS) were performed on samples embedded in resin and polished using SiC paper and diamond paste down to 1 µm. A thin layer of gold was deposited on their surfaces before metallographic analyses.
Data collection: CrysAlis CCD (Oxford Diffraction, 2003); cell refinement: CrysAlis CCD; data reduction: CrysAlis RED (Oxford Diffraction, 2003); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: DIAMOND (Bergerhoff, 1996); software used to prepare material for publication: SHELXL97.
Fig. 1. (a) UCoAl4 viewed down the c axis. (b) LaCoAl4 viewed down the b axis. Open and filled circles represent atoms at z = 0, and hatched circles represent atoms at z = 1/2. |
UCoAl4 | Dx = 6.746 Mg m−3 |
Mr = 404.88 | Mo Kα radiation, λ = 0.71073 Å |
Hexagonal, P62m | Cell parameters from 2952 reflections |
Hall symbol: P -6 -2 | θ = 4.5–46.0° |
a = 9.161 (1) Å | µ = 45.38 mm−1 |
c = 4.114 (1) Å | T = 293 K |
V = 299.01 (9) Å3 | Prism, black |
Z = 3 | 0.11 × 0.02 × 0.02 mm |
F(000) = 513 |
Kuma KM4 CCD area-detector diffractometer | 1001 independent reflections |
Radiation source: fine-focus sealed tube | 949 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.041 |
ω scans | θmax = 46.1°, θmin = 4.5° |
Absorption correction: analytical SHELXL70 in CrysAlis; Oxford Diffraction, 2003) | h = −18→14 |
Tmin = 0.038, Tmax = 0.468 | k = −17→17 |
5480 measured reflections | l = −8→5 |
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | w = 1/[σ2(Fo2) + (0.0168P)2] where P = (Fo2 + 2Fc2)/3 |
R[F2 > 2σ(F2)] = 0.022 | (Δ/σ)max < 0.001 |
wR(F2) = 0.037 | Δρmax = 2.42 e Å−3 |
S = 1.01 | Δρmin = −1.91 e Å−3 |
1001 reflections | Extinction correction: SHELXL97 (Sheldrick, 1997), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
25 parameters | Extinction coefficient: 0.0154 (5) |
0 restraints | Absolute structure: Flack (1983), 561 Friedel pairs |
Primary atom site location: structure-invariant direct methods | Absolute structure parameter: 0.046 (7) |
UCoAl4 | Z = 3 |
Mr = 404.88 | Mo Kα radiation |
Hexagonal, P62m | µ = 45.38 mm−1 |
a = 9.161 (1) Å | T = 293 K |
c = 4.114 (1) Å | 0.11 × 0.02 × 0.02 mm |
V = 299.01 (9) Å3 |
Kuma KM4 CCD area-detector diffractometer | 1001 independent reflections |
Absorption correction: analytical SHELXL70 in CrysAlis; Oxford Diffraction, 2003) | 949 reflections with I > 2σ(I) |
Tmin = 0.038, Tmax = 0.468 | Rint = 0.041 |
5480 measured reflections |
R[F2 > 2σ(F2)] = 0.022 | 0 restraints |
wR(F2) = 0.037 | Δρmax = 2.42 e Å−3 |
S = 1.01 | Δρmin = −1.91 e Å−3 |
1001 reflections | Absolute structure: Flack (1983), 561 Friedel pairs |
25 parameters | Absolute structure parameter: 0.046 (7) |
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. |
Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger. |
x | y | z | Uiso*/Ueq | ||
U | 0.40522 (2) | 0.0000 | 0.0000 | 0.00660 (4) | |
Co1 | 0.0000 | 0.0000 | 0.0000 | 0.0088 (2) | |
Co2 | 0.3333 | 0.6667 | 0.0000 | 0.01168 (19) | |
Al1 | 0.29637 (16) | 0.47944 (17) | 0.5000 | 0.0078 (2) | |
Al2 | 0.16977 (19) | 0.0000 | 0.5000 | 0.0075 (3) | |
Al3 | 0.7420 (3) | 0.0000 | 0.0000 | 0.0116 (3) |
U11 | U22 | U33 | U12 | U13 | U23 | |
U | 0.00699 (6) | 0.00747 (8) | 0.00550 (7) | 0.00373 (4) | 0.000 | 0.000 |
Co1 | 0.0086 (3) | 0.0086 (3) | 0.0092 (6) | 0.00429 (16) | 0.000 | 0.000 |
Co2 | 0.0151 (3) | 0.0151 (3) | 0.0049 (4) | 0.00753 (15) | 0.000 | 0.000 |
Al1 | 0.0085 (5) | 0.0077 (5) | 0.0070 (5) | 0.0040 (5) | 0.000 | 0.000 |
Al2 | 0.0102 (5) | 0.0083 (7) | 0.0035 (6) | 0.0042 (4) | 0.000 | 0.000 |
Al3 | 0.0110 (5) | 0.0148 (9) | 0.0102 (8) | 0.0074 (4) | 0.000 | 0.000 |
U—Co2i | 2.7834 (3) | Al1—Al1xviii | 2.725 (2) |
U—Co2ii | 2.7834 (3) | Al1—Al1xvii | 2.725 (2) |
U—Al2iii | 2.9806 (13) | Al1—Al2xiv | 2.7780 (17) |
U—Al2 | 2.9806 (13) | Al1—Al3xi | 2.7851 (14) |
U—Al3 | 3.085 (2) | Al1—Al3xxii | 2.7851 (14) |
U—Al1iv | 3.1516 (10) | Al1—Al1ix | 2.905 (2) |
U—Al1v | 3.1516 (10) | Al1—Uxxii | 3.1516 (10) |
U—Al1vi | 3.1516 (10) | Al1—Uxi | 3.1516 (10) |
U—Al1vii | 3.1516 (10) | Al1—Uxiv | 3.1967 (10) |
U—Al1viii | 3.1967 (10) | Al1—Uxxiii | 3.1967 (10) |
U—Al1ix | 3.1967 (10) | Al2—Co1xxi | 2.5788 (11) |
U—Al1x | 3.1967 (10) | Al2—Al2x | 2.694 (3) |
Co1—Al3xi | 2.364 (2) | Al2—Al2xiv | 2.694 (3) |
Co1—Al3xii | 2.364 (2) | Al2—Al1ix | 2.7780 (17) |
Co1—Al3xiii | 2.364 (2) | Al2—Al1x | 2.7780 (16) |
Co1—Al2viii | 2.5788 (11) | Al2—Al3xii | 2.9259 (13) |
Co1—Al2xiv | 2.5788 (11) | Al2—Al3xxii | 2.9259 (13) |
Co1—Al2 | 2.5788 (11) | Al2—Al3xi | 2.9259 (13) |
Co1—Al2iii | 2.5788 (11) | Al2—Al3xxiv | 2.9259 (13) |
Co1—Al2xv | 2.5788 (11) | Al2—Uxxi | 2.9806 (13) |
Co1—Al2x | 2.5788 (11) | Al3—Co1xxv | 2.364 (2) |
Co2—Al1xvi | 2.5898 (9) | Al3—Al1v | 2.7851 (14) |
Co2—Al1xvii | 2.5898 (9) | Al3—Al1iv | 2.7851 (14) |
Co2—Al1xviii | 2.5898 (9) | Al3—Al1vii | 2.7851 (14) |
Co2—Al1iii | 2.5898 (9) | Al3—Al1vi | 2.7851 (14) |
Co2—Al1xix | 2.5898 (9) | Al3—Al2vi | 2.9259 (13) |
Co2—Al1 | 2.5898 (9) | Al3—Al2xxvi | 2.9259 (13) |
Co2—Uxx | 2.7834 (3) | Al3—Al2xxvii | 2.9259 (13) |
Co2—Uxiv | 2.7834 (3) | Al3—Al2v | 2.9259 (13) |
Co2—Uxi | 2.7834 (3) | Al3—Uvi | 3.2547 (5) |
Al1—Co2xxi | 2.5898 (9) | Al3—Uxxvii | 3.2547 (5) |
Co2i—U—Co2ii | 143.649 (7) | Al1xviii—Al1—Uxxii | 65.44 (5) |
Co2i—U—Al2iii | 103.046 (6) | Al1xvii—Al1—Uxxii | 109.92 (4) |
Co2ii—U—Al2iii | 103.046 (6) | Al2xiv—Al1—Uxxii | 125.69 (4) |
Co2i—U—Al2 | 103.046 (6) | Al3xi—Al1—Uxxii | 119.91 (5) |
Co2ii—U—Al2 | 103.046 (6) | Al3xxii—Al1—Uxxii | 62.26 (5) |
Al2iii—U—Al2 | 87.28 (5) | Al1ix—Al1—Uxxii | 62.56 (2) |
Co2i—U—Al3 | 71.824 (4) | Co2xxi—Al1—Uxi | 119.48 (5) |
Co2ii—U—Al3 | 71.824 (4) | Co2—Al1—Uxi | 56.994 (18) |
Al2iii—U—Al3 | 136.36 (2) | Al1xviii—Al1—Uxi | 65.44 (5) |
Al2—U—Al3 | 136.36 (2) | Al1xvii—Al1—Uxi | 109.92 (4) |
Co2i—U—Al1iv | 104.49 (2) | Al2xiv—Al1—Uxi | 125.69 (4) |
Co2ii—U—Al1iv | 51.286 (19) | Al3xi—Al1—Uxi | 62.26 (5) |
Al2iii—U—Al1iv | 152.33 (2) | Al3xxii—Al1—Uxi | 119.91 (5) |
Al2—U—Al1iv | 89.13 (3) | Al1ix—Al1—Uxi | 62.56 (2) |
Al3—U—Al1iv | 53.03 (2) | Uxxii—Al1—Uxi | 81.49 (3) |
Co2i—U—Al1v | 51.286 (19) | Co2xxi—Al1—Uxiv | 117.90 (4) |
Co2ii—U—Al1v | 104.49 (2) | Co2—Al1—Uxiv | 56.335 (17) |
Al2iii—U—Al1v | 89.13 (3) | Al1xviii—Al1—Uxiv | 108.63 (3) |
Al2—U—Al1v | 152.33 (2) | Al1xvii—Al1—Uxiv | 63.72 (4) |
Al3—U—Al1v | 53.03 (2) | Al2xiv—Al1—Uxiv | 59.36 (3) |
Al1iv—U—Al1v | 106.07 (4) | Al3xi—Al1—Uxiv | 65.51 (3) |
Co2i—U—Al1vi | 51.286 (19) | Al3xxii—Al1—Uxiv | 122.41 (6) |
Co2ii—U—Al1vi | 104.49 (2) | Al1ix—Al1—Uxiv | 123.46 (2) |
Al2iii—U—Al1vi | 152.33 (2) | Uxxii—Al1—Uxiv | 173.41 (5) |
Al2—U—Al1vi | 89.13 (3) | Uxi—Al1—Uxiv | 98.825 (15) |
Al3—U—Al1vi | 53.03 (2) | Co2xxi—Al1—Uxxiii | 56.335 (17) |
Al1iv—U—Al1vi | 54.88 (4) | Co2—Al1—Uxxiii | 117.90 (4) |
Al1v—U—Al1vi | 81.49 (3) | Al1xviii—Al1—Uxxiii | 108.63 (3) |
Co2i—U—Al1vii | 104.49 (2) | Al1xvii—Al1—Uxxiii | 63.72 (4) |
Co2ii—U—Al1vii | 51.286 (19) | Al2xiv—Al1—Uxxiii | 59.36 (3) |
Al2iii—U—Al1vii | 89.13 (3) | Al3xi—Al1—Uxxiii | 122.41 (6) |
Al2—U—Al1vii | 152.33 (2) | Al3xxii—Al1—Uxxiii | 65.51 (3) |
Al3—U—Al1vii | 53.03 (2) | Al1ix—Al1—Uxxiii | 123.46 (2) |
Al1iv—U—Al1vii | 81.49 (3) | Uxxii—Al1—Uxxiii | 98.825 (15) |
Al1v—U—Al1vii | 54.88 (4) | Uxi—Al1—Uxxiii | 173.41 (5) |
Al1vi—U—Al1vii | 106.07 (4) | Uxiv—Al1—Uxxiii | 80.10 (3) |
Co2i—U—Al1viii | 50.75 (2) | Co1—Al2—Co1xxi | 105.82 (6) |
Co2ii—U—Al1viii | 139.903 (16) | Co1—Al2—Al2x | 58.51 (3) |
Al2iii—U—Al1viii | 53.31 (3) | Co1xxi—Al2—Al2x | 58.51 (3) |
Al2—U—Al1viii | 106.90 (2) | Co1—Al2—Al2xiv | 58.51 (3) |
Al3—U—Al1viii | 102.24 (2) | Co1xxi—Al2—Al2xiv | 58.51 (3) |
Al1iv—U—Al1viii | 152.429 (8) | Al2x—Al2—Al2xiv | 60.0 |
Al1v—U—Al1viii | 50.84 (4) | Co1—Al2—Al1ix | 108.734 (14) |
Al1vi—U—Al1viii | 102.03 (3) | Co1xxi—Al2—Al1ix | 108.734 (14) |
Al1vii—U—Al1viii | 92.663 (14) | Al2x—Al2—Al1ix | 152.18 (4) |
Co2i—U—Al1ix | 139.903 (16) | Al2xiv—Al2—Al1ix | 92.18 (4) |
Co2ii—U—Al1ix | 50.75 (2) | Co1—Al2—Al1x | 108.734 (14) |
Al2iii—U—Al1ix | 106.90 (2) | Co1xxi—Al2—Al1x | 108.734 (14) |
Al2—U—Al1ix | 53.31 (3) | Al2x—Al2—Al1x | 92.18 (4) |
Al3—U—Al1ix | 102.24 (2) | Al2xiv—Al2—Al1x | 152.18 (4) |
Al1iv—U—Al1ix | 50.84 (4) | Al1ix—Al2—Al1x | 115.64 (8) |
Al1v—U—Al1ix | 152.429 (8) | Co1—Al2—Al3xii | 50.38 (4) |
Al1vi—U—Al1ix | 92.663 (14) | Co1xxi—Al2—Al3xii | 118.94 (5) |
Al1vii—U—Al1ix | 102.03 (3) | Al2x—Al2—Al3xii | 62.59 (3) |
Al1viii—U—Al1ix | 155.52 (5) | Al2xiv—Al2—Al3xii | 103.85 (4) |
Co2i—U—Al1x | 50.75 (2) | Al1ix—Al2—Al3xii | 131.31 (4) |
Co2ii—U—Al1x | 139.903 (16) | Al1x—Al2—Al3xii | 58.39 (4) |
Al2iii—U—Al1x | 106.90 (2) | Co1—Al2—Al3xxii | 118.94 (5) |
Al2—U—Al1x | 53.31 (3) | Co1xxi—Al2—Al3xxii | 50.38 (4) |
Al3—U—Al1x | 102.24 (2) | Al2x—Al2—Al3xxii | 103.85 (4) |
Al1iv—U—Al1x | 92.663 (14) | Al2xiv—Al2—Al3xxii | 62.59 (3) |
Al1v—U—Al1x | 102.03 (3) | Al1ix—Al2—Al3xxii | 58.39 (4) |
Al1vi—U—Al1x | 50.84 (4) | Al1x—Al2—Al3xxii | 131.31 (4) |
Al1vii—U—Al1x | 152.429 (8) | Al3xii—Al2—Al3xxii | 165.34 (8) |
Al1viii—U—Al1x | 80.10 (3) | Co1—Al2—Al3xi | 50.38 (4) |
Al1ix—U—Al1x | 94.70 (4) | Co1xxi—Al2—Al3xi | 118.94 (5) |
Al3xi—Co1—Al3xii | 120.0 | Al2x—Al2—Al3xi | 103.85 (4) |
Al3xi—Co1—Al3xiii | 120.0 | Al2xiv—Al2—Al3xi | 62.59 (3) |
Al3xii—Co1—Al3xiii | 120.0 | Al1ix—Al2—Al3xi | 58.39 (4) |
Al3xi—Co1—Al2viii | 127.09 (3) | Al1x—Al2—Al3xi | 131.31 (4) |
Al3xii—Co1—Al2viii | 72.450 (13) | Al3xii—Al2—Al3xi | 88.79 (6) |
Al3xiii—Co1—Al2viii | 72.450 (13) | Al3xxii—Al2—Al3xi | 89.34 (5) |
Al3xi—Co1—Al2xiv | 72.450 (13) | Co1—Al2—Al3xxiv | 118.94 (5) |
Al3xii—Co1—Al2xiv | 127.09 (3) | Co1xxi—Al2—Al3xxiv | 50.38 (4) |
Al3xiii—Co1—Al2xiv | 72.450 (13) | Al2x—Al2—Al3xxiv | 62.59 (3) |
Al2viii—Co1—Al2xiv | 144.90 (3) | Al2xiv—Al2—Al3xxiv | 103.85 (4) |
Al3xi—Co1—Al2 | 72.450 (13) | Al1ix—Al2—Al3xxiv | 131.31 (4) |
Al3xii—Co1—Al2 | 72.450 (13) | Al1x—Al2—Al3xxiv | 58.39 (4) |
Al3xiii—Co1—Al2 | 127.09 (3) | Al3xii—Al2—Al3xxiv | 89.34 (5) |
Al2viii—Co1—Al2 | 144.90 (3) | Al3xxii—Al2—Al3xxiv | 88.79 (6) |
Al2xiv—Co1—Al2 | 62.97 (5) | Al3xi—Al2—Al3xxiv | 165.34 (8) |
Al3xi—Co1—Al2iii | 72.450 (13) | Co1—Al2—Uxxi | 170.73 (5) |
Al3xii—Co1—Al2iii | 72.450 (13) | Co1xxi—Al2—Uxxi | 83.451 (17) |
Al3xiii—Co1—Al2iii | 127.09 (3) | Al2x—Al2—Uxxi | 128.810 (19) |
Al2viii—Co1—Al2iii | 62.97 (5) | Al2xiv—Al2—Uxxi | 128.810 (19) |
Al2xiv—Co1—Al2iii | 144.90 (3) | Al1ix—Al2—Uxxi | 67.33 (4) |
Al2—Co1—Al2iii | 105.82 (6) | Al1x—Al2—Uxxi | 67.33 (4) |
Al3xi—Co1—Al2xv | 72.450 (13) | Al3xii—Al2—Uxxi | 125.28 (5) |
Al3xii—Co1—Al2xv | 127.09 (3) | Al3xxii—Al2—Uxxi | 66.869 (18) |
Al3xiii—Co1—Al2xv | 72.450 (13) | Al3xi—Al2—Uxxi | 125.28 (5) |
Al2viii—Co1—Al2xv | 62.97 (5) | Al3xxiv—Al2—Uxxi | 66.869 (18) |
Al2xiv—Co1—Al2xv | 105.82 (6) | Co1—Al2—U | 83.451 (17) |
Al2—Co1—Al2xv | 144.90 (3) | Co1xxi—Al2—U | 170.73 (5) |
Al2iii—Co1—Al2xv | 62.97 (5) | Al2x—Al2—U | 128.809 (19) |
Al3xi—Co1—Al2x | 127.09 (3) | Al2xiv—Al2—U | 128.810 (19) |
Al3xii—Co1—Al2x | 72.450 (13) | Al1ix—Al2—U | 67.33 (4) |
Al3xiii—Co1—Al2x | 72.450 (13) | Al1x—Al2—U | 67.33 (4) |
Al2viii—Co1—Al2x | 105.82 (6) | Al3xii—Al2—U | 66.869 (18) |
Al2xiv—Co1—Al2x | 62.97 (5) | Al3xxii—Al2—U | 125.28 (5) |
Al2—Co1—Al2x | 62.97 (5) | Al3xi—Al2—U | 66.869 (18) |
Al2iii—Co1—Al2x | 144.90 (3) | Al3xxiv—Al2—U | 125.28 (5) |
Al2xv—Co1—Al2x | 144.90 (3) | Uxxi—Al2—U | 87.28 (5) |
Al1xvi—Co2—Al1xvii | 105.17 (5) | Co1xxv—Al3—Al1v | 115.29 (5) |
Al1xvi—Co2—Al1xviii | 144.63 (2) | Co1xxv—Al3—Al1iv | 115.29 (5) |
Al1xvii—Co2—Al1xviii | 63.49 (4) | Al1v—Al3—Al1iv | 129.42 (10) |
Al1xvi—Co2—Al1iii | 63.49 (4) | Co1xxv—Al3—Al1vii | 115.29 (5) |
Al1xvii—Co2—Al1iii | 144.63 (2) | Al1v—Al3—Al1vii | 62.87 (5) |
Al1xviii—Co2—Al1iii | 144.63 (2) | Al1iv—Al3—Al1vii | 95.22 (6) |
Al1xvi—Co2—Al1xix | 63.49 (4) | Co1xxv—Al3—Al1vi | 115.29 (5) |
Al1xvii—Co2—Al1xix | 144.63 (2) | Al1v—Al3—Al1vi | 95.22 (6) |
Al1xviii—Co2—Al1xix | 105.17 (5) | Al1iv—Al3—Al1vi | 62.87 (5) |
Al1iii—Co2—Al1xix | 63.49 (4) | Al1vii—Al3—Al1vi | 129.42 (10) |
Al1xvi—Co2—Al1 | 144.63 (2) | Co1xxv—Al3—Al2vi | 57.17 (4) |
Al1xvii—Co2—Al1 | 63.49 (4) | Al1v—Al3—Al2vi | 172.26 (9) |
Al1xviii—Co2—Al1 | 63.49 (4) | Al1iv—Al3—Al2vi | 58.15 (4) |
Al1iii—Co2—Al1 | 105.17 (5) | Al1vii—Al3—Al2vi | 120.72 (4) |
Al1xix—Co2—Al1 | 144.63 (2) | Al1vi—Al3—Al2vi | 87.27 (3) |
Al1xvi—Co2—Uxx | 72.91 (3) | Co1xxv—Al3—Al2xxvi | 57.17 (4) |
Al1xvii—Co2—Uxx | 72.91 (3) | Al1v—Al3—Al2xxvi | 58.15 (4) |
Al1xviii—Co2—Uxx | 71.72 (3) | Al1iv—Al3—Al2xxvi | 172.26 (9) |
Al1iii—Co2—Uxx | 127.41 (2) | Al1vii—Al3—Al2xxvi | 87.27 (3) |
Al1xix—Co2—Uxx | 71.72 (3) | Al1vi—Al3—Al2xxvi | 120.72 (4) |
Al1—Co2—Uxx | 127.41 (2) | Al2vi—Al3—Al2xxvi | 114.35 (9) |
Al1xvi—Co2—Uxiv | 71.72 (3) | Co1xxv—Al3—Al2xxvii | 57.17 (4) |
Al1xvii—Co2—Uxiv | 71.72 (3) | Al1v—Al3—Al2xxvii | 120.72 (4) |
Al1xviii—Co2—Uxiv | 127.41 (2) | Al1iv—Al3—Al2xxvii | 87.27 (3) |
Al1iii—Co2—Uxiv | 72.91 (3) | Al1vii—Al3—Al2xxvii | 172.26 (9) |
Al1xix—Co2—Uxiv | 127.41 (2) | Al1vi—Al3—Al2xxvii | 58.15 (4) |
Al1—Co2—Uxiv | 72.91 (3) | Al2vi—Al3—Al2xxvii | 54.82 (7) |
Uxx—Co2—Uxiv | 120.0 | Al2xxvi—Al3—Al2xxvii | 89.34 (5) |
Al1xvi—Co2—Uxi | 127.41 (2) | Co1xxv—Al3—Al2v | 57.17 (4) |
Al1xvii—Co2—Uxi | 127.41 (2) | Al1v—Al3—Al2v | 87.27 (3) |
Al1xviii—Co2—Uxi | 72.91 (3) | Al1iv—Al3—Al2v | 120.72 (4) |
Al1iii—Co2—Uxi | 71.72 (3) | Al1vii—Al3—Al2v | 58.15 (4) |
Al1xix—Co2—Uxi | 72.91 (3) | Al1vi—Al3—Al2v | 172.26 (9) |
Al1—Co2—Uxi | 71.72 (3) | Al2vi—Al3—Al2v | 89.34 (5) |
Uxx—Co2—Uxi | 120.0 | Al2xxvi—Al3—Al2v | 54.82 (7) |
Uxiv—Co2—Uxi | 120.0 | Al2xxvii—Al3—Al2v | 114.35 (9) |
Co2xxi—Al1—Co2 | 105.17 (5) | Co1xxv—Al3—U | 180.0 |
Co2xxi—Al1—Al1xviii | 58.253 (19) | Al1v—Al3—U | 64.71 (5) |
Co2—Al1—Al1xviii | 58.253 (19) | Al1iv—Al3—U | 64.71 (5) |
Co2xxi—Al1—Al1xvii | 58.253 (19) | Al1vii—Al3—U | 64.71 (5) |
Co2—Al1—Al1xvii | 58.253 (19) | Al1vi—Al3—U | 64.71 (5) |
Al1xviii—Al1—Al1xvii | 60.0 | Al2vi—Al3—U | 122.83 (4) |
Co2xxi—Al1—Al2xiv | 114.44 (4) | Al2xxvi—Al3—U | 122.83 (4) |
Co2—Al1—Al2xiv | 114.44 (4) | Al2xxvii—Al3—U | 122.83 (4) |
Al1xviii—Al1—Al2xiv | 162.92 (7) | Al2v—Al3—U | 122.83 (4) |
Al1xvii—Al1—Al2xiv | 102.92 (7) | Co1xxv—Al3—Uvi | 81.03 (4) |
Co2xxi—Al1—Al3xi | 174.94 (4) | Al1v—Al3—Uvi | 125.57 (3) |
Co2—Al1—Al3xi | 79.80 (3) | Al1iv—Al3—Uvi | 63.35 (2) |
Al1xviii—Al1—Al3xi | 125.12 (6) | Al1vii—Al3—Uvi | 63.35 (2) |
Al1xvii—Al1—Al3xi | 126.30 (4) | Al1vi—Al3—Uvi | 125.57 (3) |
Al2xiv—Al1—Al3xi | 63.47 (5) | Al2vi—Al3—Uvi | 57.37 (3) |
Co2xxi—Al1—Al3xxii | 79.80 (3) | Al2xxvi—Al3—Uvi | 111.73 (5) |
Co2—Al1—Al3xxii | 174.94 (4) | Al2xxvii—Al3—Uvi | 111.73 (5) |
Al1xviii—Al1—Al3xxii | 125.12 (6) | Al2v—Al3—Uvi | 57.37 (3) |
Al1xvii—Al1—Al3xxii | 126.30 (4) | U—Al3—Uvi | 98.97 (4) |
Al2xiv—Al1—Al3xxii | 63.47 (5) | Co1xxv—Al3—Uxxvii | 81.03 (4) |
Al3xi—Al1—Al3xxii | 95.22 (6) | Al1v—Al3—Uxxvii | 63.35 (2) |
Co2xxi—Al1—Al1ix | 117.41 (2) | Al1iv—Al3—Uxxvii | 125.57 (3) |
Co2—Al1—Al1ix | 117.41 (2) | Al1vii—Al3—Uxxvii | 125.57 (3) |
Al1xviii—Al1—Al1ix | 109.26 (5) | Al1vi—Al3—Uxxvii | 63.35 (2) |
Al1xvii—Al1—Al1ix | 169.26 (5) | Al2vi—Al3—Uxxvii | 111.73 (5) |
Al2xiv—Al1—Al1ix | 87.82 (4) | Al2xxvi—Al3—Uxxvii | 57.37 (3) |
Al3xi—Al1—Al1ix | 58.57 (3) | Al2xxvii—Al3—Uxxvii | 57.37 (3) |
Al3xxii—Al1—Al1ix | 58.57 (3) | Al2v—Al3—Uxxvii | 111.73 (5) |
Co2xxi—Al1—Uxxii | 56.994 (18) | U—Al3—Uxxvii | 98.97 (4) |
Co2—Al1—Uxxii | 119.48 (5) | Uvi—Al3—Uxxvii | 162.06 (8) |
Symmetry codes: (i) x, y−1, z; (ii) y, x, −z; (iii) x, y, z−1; (iv) −x+1, −x+y, −z+1; (v) −y+1, x−y, z−1; (vi) −y+1, x−y, z; (vii) −x+1, −x+y, −z; (viii) −x+y, −x, z−1; (ix) y, x, −z+1; (x) −x+y, −x, z; (xi) −x+y+1, −x+1, z; (xii) −y, x−y−1, z; (xiii) x−1, y, z; (xiv) −y, x−y, z; (xv) −y, x−y, z−1; (xvi) −x+y, −x+1, z−1; (xvii) −x+y, −x+1, z; (xviii) −y+1, x−y+1, z; (xix) −y+1, x−y+1, z−1; (xx) x, y+1, z; (xxi) x, y, z+1; (xxii) −x+y+1, −x+1, z+1; (xxiii) −y, x−y, z+1; (xxiv) −y, x−y−1, z+1; (xxv) x+1, y, z; (xxvi) −x+y+1, −x, z−1; (xxvii) −x+y+1, −x, z. |
Experimental details
Crystal data | |
Chemical formula | UCoAl4 |
Mr | 404.88 |
Crystal system, space group | Hexagonal, P62m |
Temperature (K) | 293 |
a, c (Å) | 9.161 (1), 4.114 (1) |
V (Å3) | 299.01 (9) |
Z | 3 |
Radiation type | Mo Kα |
µ (mm−1) | 45.38 |
Crystal size (mm) | 0.11 × 0.02 × 0.02 |
Data collection | |
Diffractometer | Kuma KM4 CCD area-detector diffractometer |
Absorption correction | Analytical SHELXL70 in CrysAlis; Oxford Diffraction, 2003) |
Tmin, Tmax | 0.038, 0.468 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 5480, 1001, 949 |
Rint | 0.041 |
(sin θ/λ)max (Å−1) | 1.014 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.022, 0.037, 1.01 |
No. of reflections | 1001 |
No. of parameters | 25 |
Δρmax, Δρmin (e Å−3) | 2.42, −1.91 |
Absolute structure | Flack (1983), 561 Friedel pairs |
Absolute structure parameter | 0.046 (7) |
Computer programs: CrysAlis CCD (Oxford Diffraction, 2003), CrysAlis CCD, CrysAlis RED (Oxford Diffraction, 2003), SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), DIAMOND (Bergerhoff, 1996), SHELXL97.
U—Co2i | 2.7834 (3) | Al1—Al1viii | 2.905 (2) |
U—Al2 | 2.9806 (13) | Al1—Uix | 3.1516 (10) |
U—Al3 | 3.085 (2) | Al1—Uiv | 3.1516 (10) |
U—Al1ii | 3.1516 (10) | Al1—Uv | 3.1967 (10) |
U—Al1iii | 3.1967 (10) | Al2—Co1vi | 2.5788 (11) |
Co1—Al3iv | 2.364 (2) | Al2—Al2x | 2.694 (3) |
Co1—Al2 | 2.5788 (11) | Al2—Al1x | 2.7780 (16) |
Co2—Al1 | 2.5898 (9) | Al2—Al3xi | 2.9259 (13) |
Co2—Uv | 2.7834 (3) | Al2—Uvi | 2.9806 (13) |
Al1—Co2vi | 2.5898 (9) | Al3—Co1xii | 2.364 (2) |
Al1—Al1vii | 2.725 (2) | Al3—Al1xiii | 2.7851 (14) |
Al1—Al2v | 2.7780 (17) | Al3—Al2xiv | 2.9259 (13) |
Al1—Al3iv | 2.7851 (14) | Al3—Uxiv | 3.2547 (5) |
Symmetry codes: (i) x, y−1, z; (ii) −x+1, −x+y, −z+1; (iii) −x+y, −x, z−1; (iv) −x+y+1, −x+1, z; (v) −y, x−y, z; (vi) x, y, z+1; (vii) −y+1, x−y+1, z; (viii) y, x, −z+1; (ix) −x+y+1, −x+1, z+1; (x) −x+y, −x, z; (xi) −y, x−y−1, z+1; (xii) x+1, y, z; (xiii) −y+1, x−y, z−1; (xiv) −y+1, x−y, z. |
Investigations of rare earth or actinide (R) intermetallic compounds which combine a transition metal (T) with an element of the p block (X) have led to the synthesis and characterization of numerous compounds with a wide variety of anomalous physical properties. For a given formula, compounds form between most f-block elements and various transition metals, as well as some p-block elements of the same column. In the ternary R—Co—Al systems, where R is a 4f or 5f element, the compounds RCoAl4 are reported to exist with R = La, Ce or Pr (Rykhal' et al., 1977). They adopt the orthorhombic LaCoAl4 structure type (Pmma, oP12; Rykhal' et al., 1977). During a study of the ternary U—Co—Al phase diagram, the title novel compound UCoAl4 was found in as-cast samples and its crystal structure has been determined by single-crystal X-ray diffraction.
UCoAl4 adopts a new type of structure which can be described as a succession of two layers that alternate along the hexagonal c axis. Their compositions of UCoAl and Al3 correspond to the basal planes lying at z= 0 and z = 1/2, respectively. The pure Al layer (z = 1/2) is formed by triangles, squares and pentagons of Al atoms assembled by edge-sharing (Fig. 1a). According to the Schläfli notation (Reference?), the tesselation of this slab can be described as 3454 and 3545 nets of the Al1 and Al2 sites, respectively. A double layer thus defines pentagonal, square-based and trigonal prisms, within which the U, Co and Al3 atoms are located at z = 0. Neighbouring atoms within the slab additionally cap all the rectangular faces of the various prisms.
The interatomic distances in UCoAl4 compare well those reported for other ternary U—Co—Al compounds, such as U2Co2Al (Sampaio et al., 1968) and U2Co6Al19 (Tougait et al., 2003). The structure of hexagonal UCoAl4 is closely related to that of orthorhombic LaCoAl4 (Fig. 1 b). The latter structure can also be viewed as a stacking of two kinds of layers, having the compositions LaCoAl and Al3, alternating along the short b axis. The main difference between the UCoAl4 and LaCoAl4 structures arises from a different arrangement of the building motifs within the pure Al slab which defines a 3452 net in the rare-earth compound.
UCoAl4 is a high-temperature phase. Complete chemical and structural analyses of as-cast and heat-treated samples have confirmed the presence of this compound in the as-cast samples only. Electron microprobe analysis and powder X-ray diffraction have shown the occurrence of three phases in the as-cast samples, viz. hexagonal UCoAl4 (P −62m, hP18) as the major component, cubic UAl2 − xCox (ternary extension of UAl2, MgCu2-type, Fd-3 m, cF24; Petzow et al., 1964) and monoclinic U2Co6Al19 (C2/m, mC108; Tougait et al., 2003). Annealing the samples at temperatures up to 1873 K yields a three-phase mixture of cubic UAl2 − xCox, cubic UAl3 − xCox (ternary extension of UAl3, AuCu3, Pm-3 m, cP4; Lupşa et al., 1994) and orthorhombic U2Co3Al9 (Y2Co3Ga9-type, Cmcm, oC56; Grin' et al., 1984). Thus, UCoAl4 decomposes according to the peritectic reaction UCoAl4 → UAl3 − xCox + U2Co3Al9. Due to the absence of single-phase samples, the complete investigation and interpretation of the magnetic properties of UCoAl4 has not yet been carried out.