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inorganic compounds
Pd2.28(1)Zn10.37(1)Al0.35(1), a ternary γ-brass-type structure
aDepartment of Chemistry and Ames Laboratory, Iowa State University, Ames, IA 50011, USA
*Correspondence e-mail: srini@iastate.edu
Palladium zinc aluminium (2.28/10.37/0.35), Pd2.28(1)Zn10.37(1)Al0.35(1), represents the upper limit of Al substitution into the parent cubic γ-brass Pd2+xZn11−x. The structure can be described in terms of a 26-atom cluster consisting of an inner tetrahedron (IT), an outer tetrahedron (OT), an octahedron (OH) and a cuboctahedron (CO), with the substituted Al atoms partially occupying the IT (.3m) and CO (..m) sites.
Related literature
For related literature, see: Arnberg & Westman (1972); Edström & Westman (1969
); Gross et al. (2001
); Gourdon & Miller (2006
); Harbrecht et al. (2002
); Thimmaiah & Miller (2010
). For standardization of crystal structures, see: Gelato & Parthé (1987
).
Experimental
Crystal data
|
Data collection: X-AREA (Stoe & Cie, 2009); cell X-AREA; data reduction: X-AREA; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008
); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008
); molecular graphics: DIAMOND (Brandenburg, 2009
); software used to prepare material for publication: SHELXTL (Sheldrick, 2008
).
Supporting information
https://doi.org/10.1107/S1600536810000723/mg2090sup1.cif
contains datablocks I, global. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536810000723/mg2090Isup2.hkl
The title compound was prepared from 0.5 - g mixtures of the elements (Pd foil, MPC, Ames Laboratory, 99.999%; Zn ingot, MPC, Ames Laboratory, 99.999%; Al tear drop, MPC, Ames Laboratory, 99.999%) loaded into cleaned Ta tubes, which were placed in evacuated (10-5 torr) and sealed silica tubes. The tubes were heated at 30 °C h-1 to 850 °C, kept there for 12 h, cooled to 550 °C over 12 h, equilibrated there for 3 d, and then cooled to room temperature by shutting off the furnace.
Refinement of a starting model (Gourdon & Miller, 2006) led to a mixture of 0.09 (3) Pd and 0.91 (3) Zn in the OH sites. However, the IT and CO sites, initially assumed to be fully occupied by Zn atoms, exhibited elevated isotropic displacement parameters. Modeling these sites with a mixture of Zn and Al resulted in the refined composition Pd2.28 (1)Zn10.37 (1)Al0.35 (1). Analysis of multiple crystals obtained from the same and other batches gave the same site occupancies. Within the limitation of the technique, semiquantitative energy-dispersive X-ray analysis corroborate this chemical composition. The structure was standardized by means of the program STRUCTURE TIDY (Gelato & Parthé, 1987). The highest peak and the deepest hole are located 1.26 Å and 1.18 Å, respectively, from Pd1.
Various M2Zn11 phases [M = Rh (Gross et al., 2001), Pd (Gourdon & Miller, 2006), Ir (Arnberg & Westman, 1972), Pt (Harbrecht et al., 2002)] adopt the γ-brass type structure (Pearson code cI52). To study the influence of valence electron concentration (vec) on γ-brass type phases, we attempted replacing Zn by Al in the parent Pd2 + xZn11 - x phase (Gourdon & Miller, 2006). Initially obtained as a side product, Pd2.28 (1)Zn10.37 (1)Al0.35 (1) represents the upper limit of Al substitution in the Pd2 + xZn11 - x phase. Further substitution of Al leads to 2×2×2 superstructures of γ-brass with lattice parameters ranging from 18.0700 (3) to 18.1600 (2) Å (Pearson code cF400–cF416) (Thimmaiah & Miller, 2010).
In terms of the 26-atom clusters (in bcc arrangement) commonly used to describe the structure of γ-brass, the inner tetrahedron (IT) and cuboctahedron (CO) are occupied by mixtures of Zn and Al atoms, the outer tetrahedron (OT) is fully occupied by Pd atoms, and the octahedron (OH) is occupied by a mixture of Zn and Pd atoms (Fig. 1a). Similar mixing of Zn and Pd atoms on the OH sites is observed in binary Pd2 + xZn11 - x (Gourdon & Miller, 2006; Edström & Westman, 1969). An alternative description involves four interpenetrating icosahedra, which are constructed around each OT atom and encapsulate a tetrahedron formed by IT atoms (Fig. 1 b). The IT and OT sites are each surrounded by 12 nearest neighbours [at distances of 2.666 (1)–2.789 (2) Å and 2.624 (1)–2.794 (1) Å, respectively] forming distorted icosahedra. On the other hand, the coordination numbers are 13 around the OH site [2.591 (2)–2.945 (1) Å] and 11 around the CO site [2.612 (1)–2.945 (1) Å].
For related literature, see: Arnberg & Westman (1972); Edström & Westman (1969); Gross et al. (2001); Gourdon & Miller (2006); Harbrecht et al. (2002); Thimmaiah & Miller (2010). For standardization of crystal structures, see: Gelato & Parthé (1987).
Data collection: X-AREA (Stoe & Cie, 2009); cell
X-AREA (Stoe & Cie, 2009); data reduction: X-AREA (Stoe & Cie, 2009); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2009); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).Pd2.28Zn10.37Al0.35 | Melting point: not measured K |
Mr = 929.56 | Mo Kα radiation, λ = 0.71073 Å |
Cubic, I43m | Cell parameters from 2000 reflections |
Hall symbol: I -4 2 3 | θ = 3.2–34.8° |
a = 9.1079 (11) Å | µ = 37.46 mm−1 |
V = 755.54 (16) Å3 | T = 293 K |
Z = 4 | Rectangular, silver |
F(000) = 1681 | 0.12 × 0.06 × 0.03 mm |
Dx = 8.172 Mg m−3 |
Stoe/IPDS-II diffractometer | 339 independent reflections |
Radiation source: fine-focus sealed tube | 337 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.069 |
φ and ω scans | θmax = 34.8°, θmin = 3.2° |
Absorption correction: numerical (X-SHAPE and X-RED; Stoe & Cie, 2005) | h = −14→14 |
Tmin = 0.054, Tmax = 0.465 | k = −14→13 |
11243 measured reflections | l = −14→14 |
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | w = 1/[σ2(Fo2) + (0.0249P)2 + 32.9721P] where P = (Fo2 + 2Fc2)/3 |
R[F2 > 2σ(F2)] = 0.027 | (Δ/σ)max < 0.001 |
wR(F2) = 0.068 | Δρmax = 1.05 e Å−3 |
S = 1.02 | Δρmin = −1.19 e Å−3 |
339 reflections | Extinction correction: SHELXL97 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
22 parameters | Extinction coefficient: 0.00118 (16) |
0 restraints | Absolute structure: Flack (1983) |
Primary atom site location: structure-invariant direct methods | Absolute structure parameter: 0.04 (4) |
Pd2.28Zn10.37Al0.35 | Z = 4 |
Mr = 929.56 | Mo Kα radiation |
Cubic, I43m | µ = 37.46 mm−1 |
a = 9.1079 (11) Å | T = 293 K |
V = 755.54 (16) Å3 | 0.12 × 0.06 × 0.03 mm |
Stoe/IPDS-II diffractometer | 339 independent reflections |
Absorption correction: numerical (X-SHAPE and X-RED; Stoe & Cie, 2005) | 337 reflections with I > 2σ(I) |
Tmin = 0.054, Tmax = 0.465 | Rint = 0.069 |
11243 measured reflections |
R[F2 > 2σ(F2)] = 0.027 | w = 1/[σ2(Fo2) + (0.0249P)2 + 32.9721P] where P = (Fo2 + 2Fc2)/3 |
wR(F2) = 0.068 | Δρmax = 1.05 e Å−3 |
S = 1.02 | Δρmin = −1.19 e Å−3 |
339 reflections | Absolute structure: Flack (1983) |
22 parameters | Absolute structure parameter: 0.04 (4) |
0 restraints |
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) | |
Pd1 | 0.32674 (6) | 0.32674 (6) | 0.32674 (6) | 0.0101 (3) | |
Zn1 | 0.10828 (12) | 0.10828 (12) | 0.10828 (12) | 0.0139 (5) | 0.924 (17) |
Al1 | 0.10828 (12) | 0.10828 (12) | 0.10828 (12) | 0.0139 (5) | 0.076 (17) |
Zn2 | 0.35776 (15) | 0.0000 | 0.0000 | 0.0135 (5) | 0.91 (3) |
Pd2 | 0.35776 (15) | 0.0000 | 0.0000 | 0.0135 (5) | 0.09 (3) |
Zn3 | 0.31076 (9) | 0.31076 (9) | 0.03932 (12) | 0.0162 (3) | 0.966 (13) |
Al3 | 0.31076 (9) | 0.31076 (9) | 0.03932 (12) | 0.0162 (3) | 0.034 (13) |
U11 | U22 | U33 | U12 | U13 | U23 | |
Pd1 | 0.0101 (3) | 0.0101 (3) | 0.0101 (3) | 0.0007 (2) | 0.0007 (2) | 0.0007 (2) |
Zn1 | 0.0139 (5) | 0.0139 (5) | 0.0139 (5) | 0.0029 (4) | 0.0029 (4) | 0.0029 (4) |
Al1 | 0.0139 (5) | 0.0139 (5) | 0.0139 (5) | 0.0029 (4) | 0.0029 (4) | 0.0029 (4) |
Zn2 | 0.0124 (7) | 0.0140 (6) | 0.0140 (6) | 0.000 | 0.000 | 0.0034 (5) |
Pd2 | 0.0124 (7) | 0.0140 (6) | 0.0140 (6) | 0.000 | 0.000 | 0.0034 (5) |
Zn3 | 0.0177 (4) | 0.0177 (4) | 0.0132 (5) | −0.0026 (3) | −0.0028 (2) | −0.0028 (2) |
Al3 | 0.0177 (4) | 0.0177 (4) | 0.0132 (5) | −0.0026 (3) | −0.0028 (2) | −0.0028 (2) |
Pd1—Al3i | 2.6240 (11) | Zn1—Zn3 | 2.6826 (17) |
Pd1—Zn3i | 2.6240 (11) | Zn2—Pd2vi | 2.591 (3) |
Pd1—Al3ii | 2.6240 (11) | Zn2—Zn2vi | 2.591 (3) |
Pd1—Al3iii | 2.6240 (11) | Zn2—Al3vii | 2.6115 (12) |
Pd1—Zn3ii | 2.6240 (11) | Zn2—Zn3vii | 2.6115 (12) |
Pd1—Zn3iii | 2.6240 (11) | Zn2—Al3viii | 2.6115 (12) |
Pd1—Al3iv | 2.6259 (12) | Zn2—Zn3viii | 2.6115 (12) |
Pd1—Zn3iv | 2.6259 (12) | Zn2—Zn1ix | 2.6662 (12) |
Pd1—Al3v | 2.6259 (12) | Zn2—Al1ix | 2.6662 (12) |
Pd1—Zn3v | 2.6259 (12) | Zn2—Pd1x | 2.7936 (9) |
Pd1—Zn3 | 2.6259 (12) | Zn2—Pd1xi | 2.7936 (9) |
Zn1—Zn2 | 2.6662 (12) | Zn3—Pd2i | 2.6115 (12) |
Zn1—Pd2v | 2.6662 (12) | Zn3—Zn2i | 2.6115 (12) |
Zn1—Pd2iv | 2.6662 (12) | Zn3—Pd1x | 2.6240 (11) |
Zn1—Zn2v | 2.6662 (12) | Zn3—Al3xii | 2.7245 (6) |
Zn1—Zn2iv | 2.6662 (12) | Zn3—Al3vii | 2.7245 (6) |
Zn1—Al3v | 2.6826 (17) | Zn3—Zn3xii | 2.7245 (6) |
Zn1—Al3iv | 2.6826 (17) | Zn3—Zn3vii | 2.7245 (6) |
Zn1—Zn3v | 2.6826 (17) | Zn3—Al3i | 2.7245 (6) |
Zn1—Zn3iv | 2.6826 (17) | Zn3—Al3ii | 2.7245 (6) |
Al3i—Pd1—Zn3i | 0.00 (6) | Al3vii—Zn2—Zn3vii | 0.00 (5) |
Al3i—Pd1—Al3ii | 118.459 (14) | Pd2vi—Zn2—Al3viii | 68.97 (4) |
Zn3i—Pd1—Al3ii | 118.459 (14) | Zn2vi—Zn2—Al3viii | 68.97 (4) |
Al3i—Pd1—Al3iii | 118.459 (14) | Al3vii—Zn2—Al3viii | 137.93 (7) |
Zn3i—Pd1—Al3iii | 118.459 (14) | Zn3vii—Zn2—Al3viii | 137.93 (7) |
Al3ii—Pd1—Al3iii | 118.459 (14) | Pd2vi—Zn2—Zn3viii | 68.97 (4) |
Al3i—Pd1—Zn3ii | 118.459 (14) | Zn2vi—Zn2—Zn3viii | 68.97 (4) |
Zn3i—Pd1—Zn3ii | 118.459 (14) | Al3vii—Zn2—Zn3viii | 137.93 (7) |
Al3ii—Pd1—Zn3ii | 0.00 (6) | Zn3vii—Zn2—Zn3viii | 137.93 (7) |
Al3iii—Pd1—Zn3ii | 118.459 (14) | Al3viii—Zn2—Zn3viii | 0.00 (3) |
Al3i—Pd1—Zn3iii | 118.459 (14) | Pd2vi—Zn2—Zn1 | 148.46 (4) |
Zn3i—Pd1—Zn3iii | 118.459 (14) | Zn2vi—Zn2—Zn1 | 148.46 (4) |
Al3ii—Pd1—Zn3iii | 118.459 (14) | Al3vii—Zn2—Zn1 | 107.81 (3) |
Al3iii—Pd1—Zn3iii | 0.00 (6) | Zn3vii—Zn2—Zn1 | 107.81 (3) |
Zn3ii—Pd1—Zn3iii | 118.459 (14) | Al3viii—Zn2—Zn1 | 107.81 (3) |
Al3i—Pd1—Al3iv | 62.53 (3) | Zn3viii—Zn2—Zn1 | 107.81 (3) |
Zn3i—Pd1—Al3iv | 62.53 (3) | Pd2vi—Zn2—Zn1ix | 148.46 (4) |
Al3ii—Pd1—Al3iv | 133.05 (4) | Zn2vi—Zn2—Zn1ix | 148.46 (4) |
Al3iii—Pd1—Al3iv | 62.53 (3) | Al3vii—Zn2—Zn1ix | 107.81 (3) |
Zn3ii—Pd1—Al3iv | 133.05 (4) | Zn3vii—Zn2—Zn1ix | 107.81 (3) |
Zn3iii—Pd1—Al3iv | 62.53 (3) | Al3viii—Zn2—Zn1ix | 107.81 (3) |
Al3i—Pd1—Zn3iv | 62.53 (3) | Zn3viii—Zn2—Zn1ix | 107.81 (3) |
Zn3i—Pd1—Zn3iv | 62.53 (3) | Zn1—Zn2—Zn1ix | 63.08 (9) |
Al3ii—Pd1—Zn3iv | 133.05 (4) | Pd2vi—Zn2—Al1ix | 148.46 (4) |
Al3iii—Pd1—Zn3iv | 62.53 (3) | Zn2vi—Zn2—Al1ix | 148.46 (4) |
Zn3ii—Pd1—Zn3iv | 133.05 (4) | Al3vii—Zn2—Al1ix | 107.81 (3) |
Zn3iii—Pd1—Zn3iv | 62.53 (3) | Zn3vii—Zn2—Al1ix | 107.81 (3) |
Al3iv—Pd1—Zn3iv | 0.00 (7) | Al3viii—Zn2—Al1ix | 107.81 (3) |
Al3i—Pd1—Al3v | 133.05 (4) | Zn3viii—Zn2—Al1ix | 107.81 (3) |
Zn3i—Pd1—Al3v | 133.05 (4) | Zn1—Zn2—Al1ix | 63.08 (9) |
Al3ii—Pd1—Al3v | 62.53 (3) | Zn1ix—Zn2—Al1ix | 0.00 (6) |
Al3iii—Pd1—Al3v | 62.53 (3) | Pd2vi—Zn2—Pd1x | 126.98 (3) |
Zn3ii—Pd1—Al3v | 62.53 (3) | Zn2vi—Zn2—Pd1x | 126.98 (3) |
Zn3iii—Pd1—Al3v | 62.53 (3) | Al3vii—Zn2—Pd1x | 58.01 (3) |
Al3iv—Pd1—Al3v | 83.48 (4) | Zn3vii—Zn2—Pd1x | 58.01 (3) |
Zn3iv—Pd1—Al3v | 83.48 (4) | Al3viii—Zn2—Pd1x | 164.05 (6) |
Al3i—Pd1—Zn3v | 133.05 (4) | Zn3viii—Zn2—Pd1x | 164.05 (6) |
Zn3i—Pd1—Zn3v | 133.05 (4) | Zn1—Zn2—Pd1x | 59.16 (3) |
Al3ii—Pd1—Zn3v | 62.53 (3) | Zn1ix—Zn2—Pd1x | 59.16 (3) |
Al3iii—Pd1—Zn3v | 62.53 (3) | Al1ix—Zn2—Pd1x | 59.16 (3) |
Zn3ii—Pd1—Zn3v | 62.53 (3) | Pd2vi—Zn2—Pd1xi | 126.98 (3) |
Zn3iii—Pd1—Zn3v | 62.53 (3) | Zn2vi—Zn2—Pd1xi | 126.98 (3) |
Al3iv—Pd1—Zn3v | 83.48 (4) | Al3vii—Zn2—Pd1xi | 164.05 (6) |
Zn3iv—Pd1—Zn3v | 83.48 (4) | Zn3vii—Zn2—Pd1xi | 164.05 (6) |
Al3v—Pd1—Zn3v | 0.00 (7) | Al3viii—Zn2—Pd1xi | 58.01 (3) |
Al3i—Pd1—Zn3 | 62.53 (3) | Zn3viii—Zn2—Pd1xi | 58.01 (3) |
Zn3i—Pd1—Zn3 | 62.53 (3) | Zn1—Zn2—Pd1xi | 59.16 (3) |
Al3ii—Pd1—Zn3 | 62.53 (3) | Zn1ix—Zn2—Pd1xi | 59.16 (3) |
Al3iii—Pd1—Zn3 | 133.05 (4) | Al1ix—Zn2—Pd1xi | 59.16 (3) |
Zn3ii—Pd1—Zn3 | 62.53 (3) | Pd1x—Zn2—Pd1xi | 106.04 (6) |
Zn3iii—Pd1—Zn3 | 133.05 (4) | Pd2i—Zn3—Zn2i | 0.00 (5) |
Al3iv—Pd1—Zn3 | 83.48 (4) | Pd2i—Zn3—Pd1x | 153.49 (6) |
Zn3iv—Pd1—Zn3 | 83.48 (4) | Zn2i—Zn3—Pd1x | 153.49 (6) |
Al3v—Pd1—Zn3 | 83.48 (4) | Pd2i—Zn3—Pd1 | 64.47 (4) |
Zn3v—Pd1—Zn3 | 83.48 (4) | Zn2i—Zn3—Pd1 | 64.47 (4) |
Zn2—Zn1—Pd2v | 119.582 (10) | Pd1x—Zn3—Pd1 | 142.04 (5) |
Zn2—Zn1—Pd2iv | 119.582 (10) | Pd2i—Zn3—Zn1 | 145.42 (6) |
Pd2v—Zn1—Pd2iv | 119.582 (10) | Zn2i—Zn3—Zn1 | 145.42 (6) |
Zn2—Zn1—Zn2v | 119.582 (10) | Pd1x—Zn3—Zn1 | 61.09 (5) |
Pd2v—Zn1—Zn2v | 0.0 | Pd1—Zn3—Zn1 | 80.96 (5) |
Pd2iv—Zn1—Zn2v | 119.582 (10) | Pd2i—Zn3—Al3xii | 102.22 (4) |
Zn2—Zn1—Zn2iv | 119.582 (10) | Zn2i—Zn3—Al3xii | 102.22 (4) |
Pd2v—Zn1—Zn2iv | 119.582 (10) | Pd1x—Zn3—Al3xii | 58.77 (4) |
Pd2iv—Zn1—Zn2iv | 0.0 | Pd1—Zn3—Al3xii | 139.15 (3) |
Zn2v—Zn1—Zn2iv | 119.582 (10) | Zn1—Zn3—Al3xii | 104.13 (5) |
Zn2—Zn1—Al3v | 65.28 (2) | Pd2i—Zn3—Al3vii | 102.22 (4) |
Pd2v—Zn1—Al3v | 65.28 (2) | Zn2i—Zn3—Al3vii | 102.22 (4) |
Pd2iv—Zn1—Al3v | 135.08 (8) | Pd1x—Zn3—Al3vii | 58.77 (4) |
Zn2v—Zn1—Al3v | 65.28 (2) | Pd1—Zn3—Al3vii | 139.15 (3) |
Zn2iv—Zn1—Al3v | 135.08 (8) | Zn1—Zn3—Al3vii | 104.13 (5) |
Zn2—Zn1—Al3iv | 135.08 (8) | Al3xii—Zn3—Al3vii | 79.83 (8) |
Pd2v—Zn1—Al3iv | 65.28 (2) | Pd2i—Zn3—Zn3xii | 102.22 (4) |
Pd2iv—Zn1—Al3iv | 65.28 (2) | Zn2i—Zn3—Zn3xii | 102.22 (4) |
Zn2v—Zn1—Al3iv | 65.28 (2) | Pd1x—Zn3—Zn3xii | 58.77 (4) |
Zn2iv—Zn1—Al3iv | 65.28 (2) | Pd1—Zn3—Zn3xii | 139.15 (3) |
Al3v—Zn1—Al3iv | 81.33 (6) | Zn1—Zn3—Zn3xii | 104.13 (5) |
Zn2—Zn1—Zn3v | 65.28 (2) | Al3xii—Zn3—Zn3xii | 0.00 (6) |
Pd2v—Zn1—Zn3v | 65.28 (2) | Al3vii—Zn3—Zn3xii | 79.83 (8) |
Pd2iv—Zn1—Zn3v | 135.08 (8) | Pd2i—Zn3—Zn3vii | 102.22 (4) |
Zn2v—Zn1—Zn3v | 65.28 (2) | Zn2i—Zn3—Zn3vii | 102.22 (4) |
Zn2iv—Zn1—Zn3v | 135.08 (8) | Pd1x—Zn3—Zn3vii | 58.77 (4) |
Al3v—Zn1—Zn3v | 0.00 (6) | Pd1—Zn3—Zn3vii | 139.15 (3) |
Al3iv—Zn1—Zn3v | 81.33 (6) | Zn1—Zn3—Zn3vii | 104.13 (5) |
Zn2—Zn1—Zn3iv | 135.08 (8) | Al3xii—Zn3—Zn3vii | 79.83 (8) |
Pd2v—Zn1—Zn3iv | 65.28 (2) | Al3vii—Zn3—Zn3vii | 0.00 (4) |
Pd2iv—Zn1—Zn3iv | 65.28 (2) | Zn3xii—Zn3—Zn3vii | 79.83 (8) |
Zn2v—Zn1—Zn3iv | 65.28 (2) | Pd2i—Zn3—Al3i | 65.41 (4) |
Zn2iv—Zn1—Zn3iv | 65.28 (2) | Zn2i—Zn3—Al3i | 65.41 (4) |
Al3v—Zn1—Zn3iv | 81.33 (6) | Pd1x—Zn3—Al3i | 122.72 (4) |
Al3iv—Zn1—Zn3iv | 0.00 (6) | Pd1—Zn3—Al3i | 58.70 (3) |
Zn3v—Zn1—Zn3iv | 81.33 (6) | Zn1—Zn3—Al3i | 97.39 (5) |
Zn2—Zn1—Zn3 | 65.28 (2) | Al3xii—Zn3—Al3i | 80.50 (3) |
Pd2v—Zn1—Zn3 | 135.08 (8) | Al3vii—Zn3—Al3i | 153.76 (7) |
Pd2iv—Zn1—Zn3 | 65.28 (2) | Zn3xii—Zn3—Al3i | 80.50 (3) |
Zn2v—Zn1—Zn3 | 135.08 (8) | Zn3vii—Zn3—Al3i | 153.76 (7) |
Zn2iv—Zn1—Zn3 | 65.28 (2) | Pd2i—Zn3—Al3ii | 65.41 (4) |
Al3v—Zn1—Zn3 | 81.33 (6) | Zn2i—Zn3—Al3ii | 65.41 (4) |
Al3iv—Zn1—Zn3 | 81.33 (6) | Pd1x—Zn3—Al3ii | 122.72 (4) |
Zn3v—Zn1—Zn3 | 81.33 (6) | Pd1—Zn3—Al3ii | 58.70 (3) |
Zn3iv—Zn1—Zn3 | 81.33 (6) | Zn1—Zn3—Al3ii | 97.39 (5) |
Pd2vi—Zn2—Zn2vi | 0.0 | Al3xii—Zn3—Al3ii | 153.76 (7) |
Pd2vi—Zn2—Al3vii | 68.97 (4) | Al3vii—Zn3—Al3ii | 80.50 (3) |
Zn2vi—Zn2—Al3vii | 68.97 (4) | Zn3xii—Zn3—Al3ii | 153.76 (7) |
Pd2vi—Zn2—Zn3vii | 68.97 (4) | Zn3vii—Zn3—Al3ii | 80.50 (3) |
Zn2vi—Zn2—Zn3vii | 68.97 (4) | Al3i—Zn3—Al3ii | 111.69 (7) |
Symmetry codes: (i) −y+1/2, z+1/2, −x+1/2; (ii) z+1/2, −x+1/2, −y+1/2; (iii) −x+1/2, −y+1/2, z+1/2; (iv) z, x, y; (v) y, z, x; (vi) −x+1, −y, z; (vii) −z+1/2, −x+1/2, y−1/2; (viii) −z+1/2, x−1/2, −y+1/2; (ix) x, −y, −z; (x) −x+1/2, −y+1/2, z−1/2; (xi) −x+1/2, y−1/2, −z+1/2; (xii) −y+1/2, −z+1/2, x−1/2. |
Experimental details
Crystal data | |
Chemical formula | Pd2.28Zn10.37Al0.35 |
Mr | 929.56 |
Crystal system, space group | Cubic, I43m |
Temperature (K) | 293 |
a (Å) | 9.1079 (11) |
V (Å3) | 755.54 (16) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 37.46 |
Crystal size (mm) | 0.12 × 0.06 × 0.03 |
Data collection | |
Diffractometer | Stoe/IPDS-II |
Absorption correction | Numerical (X-SHAPE and X-RED; Stoe & Cie, 2005) |
Tmin, Tmax | 0.054, 0.465 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 11243, 339, 337 |
Rint | 0.069 |
(sin θ/λ)max (Å−1) | 0.803 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.027, 0.068, 1.02 |
No. of reflections | 339 |
No. of parameters | 22 |
w = 1/[σ2(Fo2) + (0.0249P)2 + 32.9721P] where P = (Fo2 + 2Fc2)/3 | |
Δρmax, Δρmin (e Å−3) | 1.05, −1.19 |
Absolute structure | Flack (1983) |
Absolute structure parameter | 0.04 (4) |
Computer programs: X-AREA (Stoe & Cie, 2009), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), DIAMOND (Brandenburg, 2009), SHELXTL (Sheldrick, 2008).
Acknowledgements
This work was carried out at the Ames Laboratory, which is operated for the US Department of Energy by Iowa State University under contract No. DE-AC02-07CH11358. This work was supported by the Materials Sciences Division of the Office of Basic Energy Sciences of the US Department of Energy.
References
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Various M2Zn11 phases [M = Rh (Gross et al., 2001), Pd (Gourdon & Miller, 2006), Ir (Arnberg & Westman, 1972), Pt (Harbrecht et al., 2002)] adopt the γ-brass type structure (Pearson code cI52). To study the influence of valence electron concentration (vec) on γ-brass type phases, we attempted replacing Zn by Al in the parent Pd2 + xZn11 - x phase (Gourdon & Miller, 2006). Initially obtained as a side product, Pd2.28 (1)Zn10.37 (1)Al0.35 (1) represents the upper limit of Al substitution in the Pd2 + xZn11 - x phase. Further substitution of Al leads to 2×2×2 superstructures of γ-brass with lattice parameters ranging from 18.0700 (3) to 18.1600 (2) Å (Pearson code cF400–cF416) (Thimmaiah & Miller, 2010).
In terms of the 26-atom clusters (in bcc arrangement) commonly used to describe the structure of γ-brass, the inner tetrahedron (IT) and cuboctahedron (CO) are occupied by mixtures of Zn and Al atoms, the outer tetrahedron (OT) is fully occupied by Pd atoms, and the octahedron (OH) is occupied by a mixture of Zn and Pd atoms (Fig. 1a). Similar mixing of Zn and Pd atoms on the OH sites is observed in binary Pd2 + xZn11 - x (Gourdon & Miller, 2006; Edström & Westman, 1969). An alternative description involves four interpenetrating icosahedra, which are constructed around each OT atom and encapsulate a tetrahedron formed by IT atoms (Fig. 1 b). The IT and OT sites are each surrounded by 12 nearest neighbours [at distances of 2.666 (1)–2.789 (2) Å and 2.624 (1)–2.794 (1) Å, respectively] forming distorted icosahedra. On the other hand, the coordination numbers are 13 around the OH site [2.591 (2)–2.945 (1) Å] and 11 around the CO site [2.612 (1)–2.945 (1) Å].