Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270101010009/br1341sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270101010009/br1341Isup2.hkl |
The purity of the starting materials was 99.99% for Cu and Al, and 99.9% for Y. A pressed tablet of a mixture of suitable weight% ratio of finely powdered starting materials was sintered at 773 K in 0.6 MPa Ar gas for 1 h, followed by higher temperature annealing at 1023 K for 1 h, with subsequent rapid cooling to room temperature. The sample was crushed and reheated directly to 1023 K under the same conditions as above, followed by cooling (at 20 K min-1 to 673 K) and then rapid cooling to room temperature. Upon optical microscopic examination, the alloy exhibited regular metallic hexagons. Some of the crystallites were isolated and crushed to powder form for identification by Guinier–Hägg X-ray powder diffraction. The atomic composition was verified by EDX analysis with a Jeol 820 scanning electron microscope equipped with a LINK elemental analysis system.
The highest peak in the residual density map, 1.86 e/Å3 at (0, 0, 0.1241), is 0.51 Å from the Y-position. The absorption correction was carried out with XABS2 (Parkin et al., 1995) using reflection data from the whole sphere.
Data collection: DIF4 (Stoe & Cie, 1988); cell refinement: DIF4; data reduction: REDU4 (Stoe & Cie, 1988); program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: DIAMOND (Bergerhoff, 1996).
Fig. 1. Stereoview of the unit-cell contents with ellipsoids plotted at the 90% probability level. Position M is a mixed position of Cu2 (31%) and Al2 (69%). |
YCu3Al2 | Dx = 5.747 Mg m−3 |
Mr = 332.03 | Mo Kα radiation, λ = 0.71073 Å |
Hexagonal, P6/mmm | Cell parameters from 50 reflections |
a = 5.172 (3) Å | θ = 18–22° |
c = 4.141 (2) Å | µ = 31.38 mm−1 |
V = 95.93 (9) Å3 | T = 293 K |
Z = 1 | Metallic prism, grey |
F(000) = 151 | 0.29 × 0.07 × 0.06 mm |
Stoe AED2 diffractometer | 182 reflections with I > 2σ(I) |
Radiation source: fine-focus sealed tube | Rint = 0.099 |
Graphite monochromator | θmax = 44.9°, θmin = 4.6° |
θ–2θ scans | h = −10→10 |
Absorption correction: multi-scan (XABS2; Parkin et al., 1995) | k = −10→10 |
Tmin = 0.062, Tmax = 0.152 | l = −8→7 |
2818 measured reflections | 4 standard reflections every 120 min |
196 independent reflections | intensity decay: <1% |
Refinement on F2 | 0 restraints |
Least-squares matrix: full | w = 1/[σ2(Fo2) + (0.020P)2] where P = (Fo2 + 2Fc2)/3 |
R[F2 > 2σ(F2)] = 0.021 | (Δ/σ)max < 0.001 |
wR(F2) = 0.055 | Δρmax = 1.86 e Å−3 |
S = 1.38 | Δρmin = −2.21 e Å−3 |
196 reflections | Extinction correction: SHELXL97, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
10 parameters | Extinction coefficient: 0.167 (16) |
YCu3Al2 | Z = 1 |
Mr = 332.03 | Mo Kα radiation |
Hexagonal, P6/mmm | µ = 31.38 mm−1 |
a = 5.172 (3) Å | T = 293 K |
c = 4.141 (2) Å | 0.29 × 0.07 × 0.06 mm |
V = 95.93 (9) Å3 |
Stoe AED2 diffractometer | 182 reflections with I > 2σ(I) |
Absorption correction: multi-scan (XABS2; Parkin et al., 1995) | Rint = 0.099 |
Tmin = 0.062, Tmax = 0.152 | 4 standard reflections every 120 min |
2818 measured reflections | intensity decay: <1% |
196 independent reflections |
R[F2 > 2σ(F2)] = 0.021 | 10 parameters |
wR(F2) = 0.055 | 0 restraints |
S = 1.38 | Δρmax = 1.86 e Å−3 |
196 reflections | Δρmin = −2.21 e Å−3 |
Experimental. This residual peak is most probably due to errors in the low-angle reflections. Two refinements using reflection data with 2θ > 40° and one with 2θ > 60° did not give any high residual peaks. The high internal R value is most probably an effect of the slightly irregular crystal shape together with a very high absorption coefficient. Heavily absorbing crystals give contributions to the reflection intensities proportional to the respective surface areas exposed to the X-ray beam. The internal R values calculated from the data with 2θ > 40° and the data with 2θ > 60° were not significantly improved. At present, our absorption-correction programs work on the principle of correcting the intensities of the reflections transmitted through the crystal. Attempts to use the observed shape of the crystal and analytical corrections with the use of this shape failed. |
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 | Occ. (<1) | |
Y | 0 | 0 | 0 | 0.00351 (14) | |
Cu1 | 0.3333 | 0.6667 | 0 | 0.00484 (14) | |
Cu2 | 0.5 | 0 | 0.5 | 0.00551 (15) | 0.314 (4) |
Al2 | 0.5 | 0 | 0.5 | 0.00551 (15) | 0.69 |
U11 | U22 | U33 | U12 | U13 | U23 | |
Y | 0.00227 (16) | 0.00227 (16) | 0.0060 (2) | 0.00114 (8) | 0.000 | 0.000 |
Cu1 | 0.00593 (17) | 0.00593 (17) | 0.00265 (19) | 0.00297 (8) | 0.000 | 0.000 |
Cu2 | 0.0088 (2) | 0.0015 (2) | 0.0038 (2) | 0.00076 (11) | 0.000 | 0.000 |
Al2 | 0.0088 (2) | 0.0015 (2) | 0.0038 (2) | 0.00076 (11) | 0.000 | 0.000 |
Y—Cu1i | 2.9861 (17) | Cu2—Cu1xiii | 2.5527 (10) |
Y—Cu1ii | 2.9861 (17) | Cu2—Cu1ii | 2.5527 (10) |
Y—Cu1iii | 2.9861 (17) | Cu2—Cu1iii | 2.5527 (10) |
Y—Cu1 | 2.9861 (17) | Cu2—Cu1xiv | 2.5527 (10) |
Y—Cu1iv | 2.9861 (17) | Cu2—Al2xv | 2.5860 (15) |
Y—Cu1v | 2.9861 (17) | Cu2—Al2xvi | 2.5860 (15) |
Y—Al2vi | 3.3128 (13) | Cu2—Cu2xv | 2.5860 (15) |
Y—Al2vii | 3.3128 (13) | Cu2—Cu2xvi | 2.5860 (15) |
Y—Cu2vi | 3.3128 (13) | Cu2—Al2vi | 2.5860 (15) |
Y—Cu2vii | 3.3128 (13) | Cu2—Al2xvii | 2.5860 (15) |
Y—Cu2 | 3.3128 (13) | Cu2—Cu2vi | 2.5860 (15) |
Y—Al2 | 3.3128 (13) | Cu2—Cu2xvii | 2.5860 (15) |
Cu1—Al2viii | 2.5527 (10) | Al2—Cu1xiii | 2.5527 (10) |
Cu1—Al2ix | 2.5527 (10) | Al2—Cu1ii | 2.5527 (10) |
Cu1—Cu2viii | 2.5527 (10) | Al2—Cu1iii | 2.5527 (10) |
Cu1—Cu2ix | 2.5527 (10) | Al2—Cu1xiv | 2.5527 (10) |
Cu1—Al2x | 2.5527 (10) | Al2—Al2xv | 2.5860 (15) |
Cu1—Al2xi | 2.5527 (10) | Al2—Al2xvi | 2.5860 (15) |
Cu1—Cu2x | 2.5527 (10) | Al2—Cu2xv | 2.5860 (15) |
Cu1—Cu2xi | 2.5527 (10) | Al2—Cu2xvi | 2.5860 (15) |
Cu1—Al2vi | 2.5527 (10) | Al2—Al2vi | 2.5860 (15) |
Cu1—Al2xii | 2.5527 (10) | Al2—Al2xvii | 2.5860 (15) |
Cu1—Cu2vi | 2.5527 (10) | Al2—Cu2vi | 2.5860 (15) |
Cu1—Cu2xii | 2.5527 (10) | Al2—Cu2xvii | 2.5860 (15) |
Cu1i—Y—Cu1ii | 180.0 | Cu1xiii—Cu2—Cu1ii | 180.0 |
Cu1i—Y—Cu1iii | 120.0 | Cu1xiii—Cu2—Cu1iii | 108.41 (4) |
Cu1ii—Y—Cu1iii | 60.0 | Cu1ii—Cu2—Cu1iii | 71.59 (4) |
Cu1i—Y—Cu1 | 60.0 | Cu1xiii—Cu2—Cu1xiv | 71.59 (4) |
Cu1ii—Y—Cu1 | 120.0 | Cu1ii—Cu2—Cu1xiv | 108.41 (4) |
Cu1iii—Y—Cu1 | 60.0 | Cu1iii—Cu2—Cu1xiv | 180.0 |
Cu1i—Y—Cu1iv | 60.0 | Cu1xiii—Cu2—Al2xv | 59.567 (17) |
Cu1ii—Y—Cu1iv | 120.0 | Cu1ii—Cu2—Al2xv | 120.433 (17) |
Cu1iii—Y—Cu1iv | 180.0 | Cu1iii—Cu2—Al2xv | 59.567 (17) |
Cu1—Y—Cu1iv | 120.0 | Cu1xiv—Cu2—Al2xv | 120.433 (17) |
Cu1i—Y—Cu1v | 120.0 | Cu1xiii—Cu2—Al2xvi | 120.433 (17) |
Cu1ii—Y—Cu1v | 60.0 | Cu1ii—Cu2—Al2xvi | 59.567 (17) |
Cu1iii—Y—Cu1v | 120.0 | Cu1iii—Cu2—Al2xvi | 120.433 (17) |
Cu1—Y—Cu1v | 180.0 | Cu1xiv—Cu2—Al2xvi | 59.567 (17) |
Cu1iv—Y—Cu1v | 60.0 | Al2xv—Cu2—Al2xvi | 180.0 |
Cu1i—Y—Al2vi | 90.0 | Cu1xiii—Cu2—Cu2xv | 59.567 (17) |
Cu1ii—Y—Al2vi | 90.0 | Cu1ii—Cu2—Cu2xv | 120.433 (17) |
Cu1iii—Y—Al2vi | 47.465 (15) | Cu1iii—Cu2—Cu2xv | 59.567 (17) |
Cu1—Y—Al2vi | 47.465 (15) | Cu1xiv—Cu2—Cu2xv | 120.433 (17) |
Cu1iv—Y—Al2vi | 132.535 (16) | Al2xv—Cu2—Cu2xv | 0.0 |
Cu1v—Y—Al2vi | 132.535 (15) | Al2xvi—Cu2—Cu2xv | 180.0 |
Cu1i—Y—Al2vii | 90.0 | Cu1xiii—Cu2—Cu2xvi | 120.433 (17) |
Cu1ii—Y—Al2vii | 90.0 | Cu1ii—Cu2—Cu2xvi | 59.567 (17) |
Cu1iii—Y—Al2vii | 132.535 (16) | Cu1iii—Cu2—Cu2xvi | 120.433 (17) |
Cu1—Y—Al2vii | 132.535 (15) | Cu1xiv—Cu2—Cu2xvi | 59.567 (17) |
Cu1iv—Y—Al2vii | 47.465 (15) | Al2xv—Cu2—Cu2xvi | 180.0 |
Cu1v—Y—Al2vii | 47.465 (15) | Al2xvi—Cu2—Cu2xvi | 0.0 |
Al2vi—Y—Al2vii | 180.0 | Cu2xv—Cu2—Cu2xvi | 180.0 |
Cu1i—Y—Cu2vi | 90.0 | Cu1xiii—Cu2—Al2vi | 59.567 (17) |
Cu1ii—Y—Cu2vi | 90.0 | Cu1ii—Cu2—Al2vi | 120.433 (17) |
Cu1iii—Y—Cu2vi | 47.465 (15) | Cu1iii—Cu2—Al2vi | 59.567 (17) |
Cu1—Y—Cu2vi | 47.465 (15) | Cu1xiv—Cu2—Al2vi | 120.433 (17) |
Cu1iv—Y—Cu2vi | 132.535 (16) | Al2xv—Cu2—Al2vi | 60.0 |
Cu1v—Y—Cu2vi | 132.535 (15) | Al2xvi—Cu2—Al2vi | 120.0 |
Al2vi—Y—Cu2vi | 0.0 | Cu2xv—Cu2—Al2vi | 60.0 |
Al2vii—Y—Cu2vi | 180.0 | Cu2xvi—Cu2—Al2vi | 120.0 |
Cu1i—Y—Cu2vii | 90.0 | Cu1xiii—Cu2—Al2xvii | 120.433 (17) |
Cu1ii—Y—Cu2vii | 90.0 | Cu1ii—Cu2—Al2xvii | 59.567 (17) |
Cu1iii—Y—Cu2vii | 132.535 (16) | Cu1iii—Cu2—Al2xvii | 120.433 (17) |
Cu1—Y—Cu2vii | 132.535 (15) | Cu1xiv—Cu2—Al2xvii | 59.567 (17) |
Cu1iv—Y—Cu2vii | 47.465 (15) | Al2xv—Cu2—Al2xvii | 120.0 |
Cu1v—Y—Cu2vii | 47.465 (15) | Al2xvi—Cu2—Al2xvii | 60.0 |
Al2vi—Y—Cu2vii | 180.0 | Cu2xv—Cu2—Al2xvii | 120.0 |
Al2vii—Y—Cu2vii | 0.0 | Cu2xvi—Cu2—Al2xvii | 60.0 |
Cu2vi—Y—Cu2vii | 180.0 | Al2vi—Cu2—Al2xvii | 180.0 |
Cu1i—Y—Cu2 | 132.535 (16) | Cu1xiii—Cu2—Cu2vi | 59.567 (17) |
Cu1ii—Y—Cu2 | 47.465 (16) | Cu1ii—Cu2—Cu2vi | 120.433 (17) |
Cu1iii—Y—Cu2 | 47.465 (16) | Cu1iii—Cu2—Cu2vi | 59.567 (17) |
Cu1—Y—Cu2 | 90.0 | Cu1xiv—Cu2—Cu2vi | 120.433 (17) |
Cu1iv—Y—Cu2 | 132.535 (16) | Al2xv—Cu2—Cu2vi | 60.0 |
Cu1v—Y—Cu2 | 90.0 | Al2xvi—Cu2—Cu2vi | 120.0 |
Al2vi—Y—Cu2 | 45.947 (14) | Cu2xv—Cu2—Cu2vi | 60.0 |
Al2vii—Y—Cu2 | 134.053 (14) | Cu2xvi—Cu2—Cu2vi | 120.0 |
Cu2vi—Y—Cu2 | 45.947 (14) | Al2vi—Cu2—Cu2vi | 0.0 |
Cu2vii—Y—Cu2 | 134.053 (14) | Al2xvii—Cu2—Cu2vi | 180.0 |
Cu1i—Y—Al2 | 132.535 (16) | Cu1xiii—Cu2—Cu2xvii | 120.433 (17) |
Cu1ii—Y—Al2 | 47.465 (16) | Cu1ii—Cu2—Cu2xvii | 59.567 (17) |
Cu1iii—Y—Al2 | 47.465 (16) | Cu1iii—Cu2—Cu2xvii | 120.433 (17) |
Cu1—Y—Al2 | 90.0 | Cu1xiv—Cu2—Cu2xvii | 59.567 (17) |
Cu1iv—Y—Al2 | 132.535 (16) | Al2xv—Cu2—Cu2xvii | 120.0 |
Cu1v—Y—Al2 | 90.0 | Al2xvi—Cu2—Cu2xvii | 60.0 |
Al2vi—Y—Al2 | 45.947 (14) | Cu2xv—Cu2—Cu2xvii | 120.0 |
Al2vii—Y—Al2 | 134.053 (14) | Cu2xvi—Cu2—Cu2xvii | 60.0 |
Cu2vi—Y—Al2 | 45.947 (14) | Al2vi—Cu2—Cu2xvii | 180.0 |
Cu2vii—Y—Al2 | 134.053 (14) | Al2xvii—Cu2—Cu2xvii | 0.0 |
Cu2—Y—Al2 | 0.0 | Cu2vi—Cu2—Cu2xvii | 180.0 |
Al2viii—Cu1—Al2ix | 145.991 (18) | Cu1xiii—Al2—Cu1ii | 180.0 |
Al2viii—Cu1—Cu2viii | 0.0 | Cu1xiii—Al2—Cu1iii | 108.41 (4) |
Al2ix—Cu1—Cu2viii | 145.991 (18) | Cu1ii—Al2—Cu1iii | 71.59 (4) |
Al2viii—Cu1—Cu2ix | 145.991 (18) | Cu1xiii—Al2—Cu1xiv | 71.59 (4) |
Al2ix—Cu1—Cu2ix | 0.0 | Cu1ii—Al2—Cu1xiv | 108.41 (4) |
Cu2viii—Cu1—Cu2ix | 145.991 (18) | Cu1iii—Al2—Cu1xiv | 180.0 |
Al2viii—Cu1—Al2x | 108.41 (4) | Cu1xiii—Al2—Al2xv | 59.567 (17) |
Al2ix—Cu1—Al2x | 60.87 (3) | Cu1ii—Al2—Al2xv | 120.433 (17) |
Cu2viii—Cu1—Al2x | 108.41 (4) | Cu1iii—Al2—Al2xv | 59.567 (17) |
Cu2ix—Cu1—Al2x | 60.87 (3) | Cu1xiv—Al2—Al2xv | 120.433 (17) |
Al2viii—Cu1—Al2xi | 60.87 (3) | Cu1xiii—Al2—Al2xvi | 120.433 (17) |
Al2ix—Cu1—Al2xi | 108.41 (4) | Cu1ii—Al2—Al2xvi | 59.567 (17) |
Cu2viii—Cu1—Al2xi | 60.87 (3) | Cu1iii—Al2—Al2xvi | 120.433 (17) |
Cu2ix—Cu1—Al2xi | 108.41 (4) | Cu1xiv—Al2—Al2xvi | 59.567 (17) |
Al2x—Cu1—Al2xi | 145.991 (18) | Al2xv—Al2—Al2xvi | 180.0 |
Al2viii—Cu1—Cu2x | 108.41 (4) | Cu1xiii—Al2—Cu2xv | 59.567 (17) |
Al2ix—Cu1—Cu2x | 60.87 (3) | Cu1ii—Al2—Cu2xv | 120.433 (17) |
Cu2viii—Cu1—Cu2x | 108.41 (4) | Cu1iii—Al2—Cu2xv | 59.567 (17) |
Cu2ix—Cu1—Cu2x | 60.87 (3) | Cu1xiv—Al2—Cu2xv | 120.433 (17) |
Al2x—Cu1—Cu2x | 0.0 | Al2xv—Al2—Cu2xv | 0.0 |
Al2xi—Cu1—Cu2x | 145.991 (18) | Al2xvi—Al2—Cu2xv | 180.0 |
Al2viii—Cu1—Cu2xi | 60.87 (3) | Cu1xiii—Al2—Cu2xvi | 120.433 (17) |
Al2ix—Cu1—Cu2xi | 108.41 (4) | Cu1ii—Al2—Cu2xvi | 59.567 (17) |
Cu2viii—Cu1—Cu2xi | 60.87 (3) | Cu1iii—Al2—Cu2xvi | 120.433 (17) |
Cu2ix—Cu1—Cu2xi | 108.41 (4) | Cu1xiv—Al2—Cu2xvi | 59.567 (17) |
Al2x—Cu1—Cu2xi | 145.991 (18) | Al2xv—Al2—Cu2xvi | 180.0 |
Al2xi—Cu1—Cu2xi | 0.0 | Al2xvi—Al2—Cu2xvi | 0.0 |
Cu2x—Cu1—Cu2xi | 145.991 (18) | Cu2xv—Al2—Cu2xvi | 180.0 |
Al2viii—Cu1—Al2vi | 145.991 (17) | Cu1xiii—Al2—Al2vi | 59.567 (17) |
Al2ix—Cu1—Al2vi | 60.87 (3) | Cu1ii—Al2—Al2vi | 120.433 (17) |
Cu2viii—Cu1—Al2vi | 145.991 (17) | Cu1iii—Al2—Al2vi | 59.567 (17) |
Cu2ix—Cu1—Al2vi | 60.87 (3) | Cu1xiv—Al2—Al2vi | 120.433 (17) |
Al2x—Cu1—Al2vi | 60.87 (3) | Al2xv—Al2—Al2vi | 60.0 |
Al2xi—Cu1—Al2vi | 145.991 (18) | Al2xvi—Al2—Al2vi | 120.0 |
Cu2x—Cu1—Al2vi | 60.87 (3) | Cu2xv—Al2—Al2vi | 60.0 |
Cu2xi—Cu1—Al2vi | 145.991 (18) | Cu2xvi—Al2—Al2vi | 120.0 |
Al2viii—Cu1—Al2xii | 60.87 (3) | Cu1xiii—Al2—Al2xvii | 120.433 (17) |
Al2ix—Cu1—Al2xii | 145.991 (17) | Cu1ii—Al2—Al2xvii | 59.567 (17) |
Cu2viii—Cu1—Al2xii | 60.87 (3) | Cu1iii—Al2—Al2xvii | 120.433 (17) |
Cu2ix—Cu1—Al2xii | 145.991 (17) | Cu1xiv—Al2—Al2xvii | 59.567 (17) |
Al2x—Cu1—Al2xii | 145.991 (17) | Al2xv—Al2—Al2xvii | 120.0 |
Al2xi—Cu1—Al2xii | 60.87 (3) | Al2xvi—Al2—Al2xvii | 60.0 |
Cu2x—Cu1—Al2xii | 145.991 (17) | Cu2xv—Al2—Al2xvii | 120.0 |
Cu2xi—Cu1—Al2xii | 60.87 (3) | Cu2xvi—Al2—Al2xvii | 60.0 |
Al2vi—Cu1—Al2xii | 108.41 (4) | Al2vi—Al2—Al2xvii | 180.0 |
Al2viii—Cu1—Cu2vi | 145.991 (17) | Cu1xiii—Al2—Cu2vi | 59.567 (17) |
Al2ix—Cu1—Cu2vi | 60.87 (3) | Cu1ii—Al2—Cu2vi | 120.433 (17) |
Cu2viii—Cu1—Cu2vi | 145.991 (17) | Cu1iii—Al2—Cu2vi | 59.567 (17) |
Cu2ix—Cu1—Cu2vi | 60.87 (3) | Cu1xiv—Al2—Cu2vi | 120.433 (17) |
Al2x—Cu1—Cu2vi | 60.87 (3) | Al2xv—Al2—Cu2vi | 60.0 |
Al2xi—Cu1—Cu2vi | 145.991 (18) | Al2xvi—Al2—Cu2vi | 120.0 |
Cu2x—Cu1—Cu2vi | 60.87 (3) | Cu2xv—Al2—Cu2vi | 60.0 |
Cu2xi—Cu1—Cu2vi | 145.991 (18) | Cu2xvi—Al2—Cu2vi | 120.0 |
Al2vi—Cu1—Cu2vi | 0.0 | Al2vi—Al2—Cu2vi | 0.0 |
Al2xii—Cu1—Cu2vi | 108.41 (4) | Al2xvii—Al2—Cu2vi | 180.0 |
Al2viii—Cu1—Cu2xii | 60.87 (3) | Cu1xiii—Al2—Cu2xvii | 120.433 (17) |
Al2ix—Cu1—Cu2xii | 145.991 (17) | Cu1ii—Al2—Cu2xvii | 59.567 (17) |
Cu2viii—Cu1—Cu2xii | 60.87 (3) | Cu1iii—Al2—Cu2xvii | 120.433 (17) |
Cu2ix—Cu1—Cu2xii | 145.991 (17) | Cu1xiv—Al2—Cu2xvii | 59.567 (17) |
Al2x—Cu1—Cu2xii | 145.991 (17) | Al2xv—Al2—Cu2xvii | 120.0 |
Al2xi—Cu1—Cu2xii | 60.87 (3) | Al2xvi—Al2—Cu2xvii | 60.0 |
Cu2x—Cu1—Cu2xii | 145.991 (17) | Cu2xv—Al2—Cu2xvii | 120.0 |
Cu2xi—Cu1—Cu2xii | 60.87 (3) | Cu2xvi—Al2—Cu2xvii | 60.0 |
Al2vi—Cu1—Cu2xii | 108.41 (4) | Al2vi—Al2—Cu2xvii | 180.0 |
Al2xii—Cu1—Cu2xii | 0.0 | Al2xvii—Al2—Cu2xvii | 0.0 |
Cu2vi—Cu1—Cu2xii | 108.41 (4) | Cu2vi—Al2—Cu2xvii | 180.0 |
Symmetry codes: (i) −x, −y+1, −z; (ii) x, y−1, z; (iii) −x+1, −y+1, −z; (iv) x−1, y−1, z; (v) −x, −y, −z; (vi) −x+y+1, −x+1, z; (vii) −x+y, −x, z−1; (viii) −y, x−y, z−1; (ix) x, y+1, z; (x) −y, x−y, z; (xi) x, y+1, z−1; (xii) −x+y+1, −x+1, z−1; (xiii) −x+1, −y+1, −z+1; (xiv) x, y−1, z+1; (xv) −y+1, x−y, z; (xvi) −y, x−y−1, z; (xvii) −x+y+1, −x, z. |
Experimental details
Crystal data | |
Chemical formula | YCu3Al2 |
Mr | 332.03 |
Crystal system, space group | Hexagonal, P6/mmm |
Temperature (K) | 293 |
a, c (Å) | 5.172 (3), 4.141 (2) |
V (Å3) | 95.93 (9) |
Z | 1 |
Radiation type | Mo Kα |
µ (mm−1) | 31.38 |
Crystal size (mm) | 0.29 × 0.07 × 0.06 |
Data collection | |
Diffractometer | Stoe AED2 diffractometer |
Absorption correction | Multi-scan (XABS2; Parkin et al., 1995) |
Tmin, Tmax | 0.062, 0.152 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 2818, 196, 182 |
Rint | 0.099 |
(sin θ/λ)max (Å−1) | 0.993 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.021, 0.055, 1.38 |
No. of reflections | 196 |
No. of parameters | 10 |
Δρmax, Δρmin (e Å−3) | 1.86, −2.21 |
Computer programs: DIF4 (Stoe & Cie, 1988), DIF4, REDU4 (Stoe & Cie, 1988), SHELXS97 (Sheldrick, 1990), SHELXL97 (Sheldrick, 1997), DIAMOND (Bergerhoff, 1996).
Y—Cu1 | 2.9861 (17) | Cu1—Cu2i | 2.5527 (10) |
Y—Cu2 | 3.3128 (13) | Cu2—Cu2ii | 2.5860 (15) |
Symmetry codes: (i) −y, x−y, z; (ii) −y+1, x−y, z. |
Previous investigations have shown that the light rare-earth elements, and incidentally also some heavy rare-earth elements, form a hexagonal compound of the AB5 system (CaCu5 type) as reported in the literature (Dwight, 1961; Wernick & Geller, 1959; Haszko, 1960). The stoichiometric composition of these hexagonal phases does not seem well established as some rare-earth elements have the CaCu5 structure in compounds of composition RCu4 as well as RCu5 (Gschneidner, 1961).
Studies of the intermetallic AB5 system (CaCu5 type) has shown that several properties, e.g. the hydrogen-absorption properties of the phases, can be easily varied over a wide range by the partial replacement of A or B atoms by other metals (Lanker et al., 1982; Van Vucht, Kuijpers & Bruning, 1970). Relatively large differences in the metallic radii of the A and B metals favors the stability of the AB5 phases, making them so-called `line compounds' in their binary-phase diagrams. This stability may be essential in order to obtain a homogeneous composition of the intermetallic compound.
Pure RCu5 is not stable and crystallizes in the BaAl4 type structure. It is noted that aluminium substitution stabilizes the hexagonal CaCu5 type structure for RCu4Al compounds (R = La—Sm; Takeshita et al., 1978).
The investigation of the present compound is part of a larger project aimed at finding alternative intermetallic AB5 compounds for hydrogen absorption, based on both elements lighter than lanthanides (for example, R = Y) and cheap elements (for example, substitution of a B atom in RB5-type structures by Cu and Al).
Both YCu5 and YNi5 did not show any hydrogen uptake and it was therefore of interest to study the influence of metal-atom replacement in YCu5 (Wernick & Geller, 1959; Buschow & Goot, 1971) by aluminium as the atomic radius of Al (1.432 Å) is larger than that of Cu (1.278 Å; Teatum et al., 1960), thus expanding the metal-atom lattice and possibly also providing interstitial positions for hydrogen.
The YCu5 structure (Wernick & Geller, 1959) is built from alternate layers of the CaCu5 type, viz. each Y is surrounded by six Cu atoms in one plane (at 2.88 Å) and by two more sets of six Cu atoms in adjacent planes (at 3.23 Å).
The same planes exist in YCu3Al2 but at slightly different distances (Fig. 1). The average nearest-neighbour Cu1—Cu2 distances are increased compared with those of YCu5 (2.49 and 2.51 Å; Wernick & Geller, 1959). The (Cu—Cu) distances in the present compound are close to those of a normal close-packed Cu atom with coordination number (CN) 12 (average nearest-neighbor distance = 2.56 Å; Wernick & Geller, 1959).
This compound does not show any hydrogen absorption/desorption in the pressure-composition isotherms (P—C—T diagrams) in the temperature range 298–673 K under 3.3 MPa H2 pressure using an automated Sieverts-type apparatus. No enthalpy change was observed up to 773 K in 3 MPa static hydrogen pressure by differential thermal analysis (DTA) for the present compound. No disproportion of the alloy was observed by XRD after DTA and P—C—T.