Z. Kristallogr. NCS 228 (2013) 443-444 / DOI 10.1515/ncrs.2013.0208
443
© by Oldenbourg Wissenschaftsverlag, München
Crystal structure of octa(barium, strontium)hexazinc tetracontagermanide, Ba7.56Ge40Sr0.44Zn6
Qin-Xing Xie*, I and Reinhard NesperII
I
II
School of Materials Science and Engineering, Tianjin Polytechnic University, 399 Binshui West Road, 300387 Tianjin, P. R. China
Laboratorium für Anorganische Chemie, ETH Hönggerberg-HCI, Wolfgang-Pauli-Strasse 10, CH-8093 Zürich, Switzerland
Received April 06, 2013, accepted August 19, 2013, available online October 01, 2013, CSD no. 710091
site of the small cage was mixed occupied by barium and strontium with an occupancy of 78% and 22%, respectively. Zinc (6c)
and germanium (24k and 16i) atoms are covalently bonded. The
X–X–X (X = Zn/Ge) bond angles are in a range of 104.6-124.8°,
which is very close to the ideal tetrahedral angle. X–X bond
lengths are in a range of 2.48-2.53 Å showing a similarity to those
found in crystalline germanium.
Abstract
Ba7.56Ge40Sr0.44Zn6, Pm3n (no. 223), a = 10.7753(13) Å,
V = 1251.1 Å3, Z = 1, Rgt(F) = 0.0262, wRref(F2) = 0.0375,
T = 293 K.
Table 1. Data collection and handling.
Crystal:
Wavelength:
+:
Diffractometer, scan mode:
2)max:
N(hkl)measured, N(hkl)unique:
Criterion for Iobs, N(hkl)gt:
N(param)refined:
Programs:
grey irregular shape,
size 0.10#0.12#0.14 mm
Mo K0 radiation (0.71073 Å)
327.01 cm.1
SMART PLATFORM, CCD Detector, #
62.02°
12779, 372
Iobs > 2 &(Iobs), 316
17
ORTEP-3 [2], SHELX [3], ATOMS [4]
Source of material
Ba7.56Sr0.44Zn6Ge40 was synthesized from a mixture of pure elements in stoichiometric amounts heated up to 1173 K for 72 h in
argon atmosphere. After cooling down at a rate of 50 K/h, the
product was obtained as grey crystals with metallic lustre. The
compound is stable in air and diluted hydrochloric acid solution.
Experimental details
In the structure, the mixed occupancies of Ba/Sr and Zn/Sr were
also refined, respectively.
Discussion
Ba7.56Sr0.44Zn6Ge40 crystallizes in the clathrate I [1] structure
type. It consists of two types of polyhedra, one centered at 2a
Wyckoff sites with 20 vertices, and the other centered at 6d
Wyckoff sites with 24 vertices. Those polyhedra are connected
together through the pentagonal rings. Each unit cell is built up by
two 20-atom cages and six 24-atom cages. The fully occupied 6d
site by barium atom exhibits a large displacement, while the 2a
_____________
* Correspondence author (e-mail: [email protected])
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444
Ba7.56Ge40Sr0.44Zn6
Table 2. Atomic coordinates and displacement parameters (in Å2).
Atom
Site Occ.
x
y
z
U11
U22
U33
Ba(1)
Ba(2)
Sr(2)
Ge(1)
Ge(2)
Zn(3)
6d
2a 0.782
2a 0.218
24k
16i
6c
%
0
0
0
0.18361(3)
%
"
0
0
0.30921(5)
0.18361(3)
0
0
0
0
0.11756(5)
0.18361(3)
"
0.0246(5)
0.0158(4)
0.0158(4)
0.0157(3)
0.0145(2)
0.0167(6)
0.0589(4)
0.0158(4)
0.0158(4)
0.0146(3)
0.0145(2)
0.0143(4)
0.0589(4)
0.0158(4)
0.0158(4)
0.0151(3)
0.0145(2)
0.0143(4)
Acknowledgments. This work was supported by the Tianjin National Science
Foundation under project number 10JCYBJC26200, and the Scientific
Research Foundation for the Returned Overseas Chinese Scholars (20112014).
References
U12
0
0
0
0
.0.0009(1)
0
U13
0
0
0
0
.0.0009(1)
0
U23
0
0
0
.0.0008(2)
.0.0009(1)
0
2. Farrugia, L. J.: WinGX and ORTEP for Windows: an update. J. Appl.
Crystallogr. 45 (2012) 849-854.
3. Sheldrick, G. M.: A short history of SHELX. Acta Crystallogr. A64
(2008) 112-122.
4. Dowty, E.: ATOMS Computer Program for Displaying Atomic Structures. Shape Software, Version 5.1 for Windows, 2000.
1. Kasper, J. S.; Hagenmuller, P.; Pouchard, M.; Cros, C.: Clathrate Structure of Silicon Na8Si46 and NaxSi136 (x < 11). Science. 150 (1965) 17131714.
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