The synthesis and crystal structures of the first rare-earth alkaline-earth selenite chlorides MNd10(SeO3)12Cl8 (M=Ca and Sr)

Article abstract of DOI:10.1016/j.jssc.2007.08.019

Two new alkaline-earth Nd selenite chlorides MNd₁₀(SeO₃)₁₂Cl₈ (M=Ca, Sr) were obtained using crystal growth from alkaline-earth chloride melts in quartz tubes. These new compounds crystallize in the orthorhombic system in space group C cca (#68). The compounds were studied by energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction. It was shown that both compounds adopt the same structure type, constructed by complex [M₁₁(SeO₃)₁₂]⁸⁺ slabs separated by chloride anion layers perpendicular to the longest cell parameter. The SeO₃ groups show a pyramidal shape and may be described as SeO₃E tetrahedra. Such SeO₃ groups decorate the Nd-O skeletons forming the [M₁₁(SeO₃)₁₂]⁸⁺ slabs.

Full text of DOI:10.1016/j.jssc.2007.08.019

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Journal of Solid State Chemistry 180 (2007) 3019–3025
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The synthesis and crystal structures of the first rare-earth alkaline-earth
selenite chlorides MNd10(SeO3)12Cl8 (M ¼ Ca and Sr)
Ã
P.S. Berdonosova, , A.V. Oleneva, V.A. Dolgikha, P. Lightfootb
aDepartment of Chemistry, Moscow State University, Leninskie Gory, Moscow 119992, Russia
bEaStChem, School of Chemistry, St. Andrews University, St. Andrews, KY16 9ST, UK
Received 15 June 2007; received in revised form 9 August 2007; accepted 9 August 2007
Available online 1 September 2007
Abstract
Two new alkaline-earth Nd selenite chlorides MNd10(SeO3)12Cl8 (M ¼ Ca, Sr) were obtained using crystal growth from alkaline-earth
chloride melts in quartz tubes. These new compounds crystallize in the orthorhombic system in space group C cca (#68). The compounds
were studied by energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction. It was shown that both compounds adopt the same
structure type, constructed by complex [M11(SeO3)12]8+ slabs separated by chloride anion layers perpendicular to the longest cell
parameter. The SeO3 groups show a pyramidal shape and may be described as SeO3E tetrahedra. Such SeO3 groups decorate the Nd–O
skeletons forming the [M11(SeO3)12]8+ slabs.
r 2007 Elsevier Inc. All rights reserved.
Keywords: Selenite chloride; Rare earth compound; Crystal structure
1. Introduction
may be seen, during the last 5 years a new family of
compounds–complex selenite-halogenides of REE has
begun to form. Up to now this family was presented by
alkaline metals-REE and d-metals-REE compounds only.
In the present study we describe the synthesis and crystal
structure of two new alkaline earth and neodymium
selenite chlorides, which are the first representatives of
alkaline-earth inclusion in such compounds.
Compounds which contain ions with lone electron pairs
such as Se(IV), Te(IV), Sb(III), Bi(III) and others together
with halide ions attract attention due to their possibility to
form low dimensional structures and to possess unusual
physical properties such as quantum spin systems or non
linear optical phenomena [1–3].
A rare earth (REE)-Cu compound with composition
Cu3Er(SeO3)2O2Cl with the mineral francisite structure
type was known from 1996 [4] but the first selenite-
halogenides of REE were synthesized and characterized in
2002 [5,6]. Just after that, numerous more complex
compositions of selenite-halogenides with REEs were
described: MLn(SeO3)2Cl [7], CsSm21(SeO3)24Br16 and
Bi10.67(SeO3)12Br8 [8], CsTmSeO3Cl2 [9]. Later, the family
of alkali metal-REE selenite chlorides was extended by
CsEu4O3(SeO3)2Cl3 [10], Rb6LiLn11(SeO3)12Cl12 [11,12],
Cs3La11(SeO3)12Cl16 [13], K7Sm11(SeO3)12Cl16 and
Cs7Pr11(SeO3)12Cl16 [14] and one other compound with
composition CoNd10(SeO3)12Cl8 was described [15]. As
2. Experimental
2.1. Synthesis and preliminary characterization
Single crystals of the title compounds were obtained by
the common technique described in [13] and [14]. NdOCl
was obtained by pyrohydrolysis of NdCl3 ꢀ 6H2O (chemi-
cally pure) in a tube furnace in air flow at 823 K. Selenium
dioxide was obtained by dehydratation of H2SeO3 (98%)
under vacuum at 333 K and product sublimation in a flow
of dried air with addition of NO2 followed by dehydration.
The purity of samples was confirmed by powder X-ray
diffraction testing (Stoe STADI- P system, CuKa1 radia-
tion, Ge monochromator) and using PDF2 [16]. A double
Ã
Corresponding author. Fax: +7 495 939 0998.
E-mail address: psberd@inorg.chem.msu.ru (P.S. Berdonosov).
0022-4596/$ - see front matter r 2007 Elsevier Inc. All rights reserved.
doi:10.1016/j.jssc.2007.08.019

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weight excess of anhydrous MCl2 (M ¼ Ca, Sr) (both
chemically pure) was added to the mixture of NdOCl and
SeO2 in molar ratio 1:1 under a dried argon atmosphere.
Mixtures, total weight about 0.3–0.4 g, were placed in
quartz tubes and sealed under vacuum. Tubes were loaded
into electronically controlled furnaces and preheated at
573 K for 24 h. After that the temperature was raised up to
1073 K (for CaCl2) and 1173 K (for SrCl2). After 15 min at
high temperature the furnaces were cooled at 2 K hꢁ1 down
to 673 K and then were switched off. After cooling to room
temperature, the reaction products were washed out by
water to remove excess of MCl2 and dried in air. In both
cases well-shaped plate-like crystals were observed. The
final yield of product was about 80–85% based on the
original amount of NdOCl.
The obtained crystals were analyzed by X-ray powder
diffraction after grinding and by energy dispersive X-ray
spectroscopy (EDX) using a JEOL JEM 2011 HRTEM
microscope with an Oxford Instruments ISIS EDX
Analysis System and Supra 50 VP (LEO) equipped with
INCA energy+ (Oxford) analyzing unit. According to
EDX data the compounds consist from Nd, Se and Cl as
the main part, plus a small amount of calcium or
strontium. For example, for Ca compound the following
data were obtained in atomic%: Nd 14.47(0.23), Se
16.07(0.19), Ca 1.88(0.06) and Cl 11.94(0.23) (calculated
% from finally obtained formula Nd 14.92, Se 17.91, Ca
1.49, Cl 11.94). X-ray powder pattern analysis showed the
absence of known compounds and starting materials and
the similarity of structures of Ca and Sr containing
samples.
2.2. Single crystal study
Suitable crystals were studied on Rigaku mercury CCD
diffractometer. Some crystallographic data and experimen-
tal details are summarized in Table 1.
The initial structural model was obtained in space group C
cca (68) using direct methods (Shelxs-86). Final refinement
was performed using Shelxl-97 [17] software package.
Atomic coordinates and isotropic displacement parameters
are summarized in Table 2. We have tried to refine the site
occupancy of the metal atoms in order to obtain the alkaline
earth metal distribution at the metal positions. It was shown
that the distribution of alkaline earth metal is different at the
different crystallographic sites. In both compounds alkaline
earth metal is mostly located in the Nd2 positions (site
occupancy about 17–25% of Ca or Sr). According to the
X-ray site occupation accuracy determination the composi-
tion (Table 2) of the compound is MNd10(SeO3)12Cl8,
M ¼ Ca, Sr. In the header of Table 2 the compositions of
the compounds are presented with errors according to the
X-ray solution. These formulae correlate with EDX data and
charge balance of the substances.
Further details of the crystal structure investiga-
tions may be obtained from Fachinformationszentrum
Table 1
Crystal data and structure refinement for CaNd10(SeO3)12Cl8 and SrNd10(SeO3)12Cl8
CaNd10(SeO3)12Cl8
SrNd10(SeO3)12Cl8
93(2)
Diffractometer
Temperature, K
Crystal system
Space group
Rigaku mercury CCD
93(2)
Orthorhombic
C cca (68)
˚
Cell parameters, A
a
b
c
15.588(3)
17.419(4)
15.681(3)
4257.7(14)
15.773(4)
17.622(4)
15.836(4)
4401.4(19)
3
˚
Cell volume, A
Z
4
Calculated density, g cmꢁ3
Absorption coefficient, mmꢁ1
Wavelength
5.132
22.942
5.053
23.426
MoKa
F(000)
Limiting indices
5808
5899
ꢁ17php18
ꢁ20php19
ꢁ20pkp14
ꢁ20plp20
0.10 ꢂ 0.03 ꢂ 0.03
2.18–28.14
12474
ꢁ17pkp21
ꢁ17plp19
Crystal size, mm
0.10 ꢂ 0.03 ꢂ 0.01
2.16–25.36
12493
Theta range for data collection, deg
Reflections collected
Reflections unique
2221 [R(int) ¼ 0.0426]
2221/1/153
1.241
2013 [R(int) ¼ 0.0717]
2013/31/159
1.074
Data / restraints / parameters
Goodness-of-fit on F2
Final R indices [I42s(I)]
R indices (all data)
Largest diff. peak and hole eAꢁ3
ICSD number
R1 ¼ 0.0383 wR2 ¼ 0.0976
R1 ¼ 0.0426 wR2 ¼ 0.0999
5.026 and ꢁ1.593
R1 ¼ 0.0430 wR2 ¼ 0.1092
R1 ¼ 0.0443 wR2 ¼ 0.1108
5.099 and ꢁ2.812
418191
418190

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3021
Table 2
Atomic coordinates and equivalent isotropic displacement parameters (A2 ꢂ 103) for CaNd10(SeO3)12Cl8 and SrNd10(SeO3)12Cl8
Atom
Parameter
Ca170.14Nd9.9770.14(SeO3)12Cl8 93 K
Sr170.01Nd1070.01(SeO3)12Cl8 93K
Nd1
x
1/2
1/4
1/2
1/4
y
z
1/4
3(1)
1/4
3(1)
U(eq)
x
Nd2
Nd3
Nd4
Nd5
Nd6
0.1194(1)
0.0730(1)
0.1190(1)
0.0727(1)
y
z
0.1303(1)
Nd 0.805(2) Ca 0.194(2)
0.1305(1)
Nd 0.7499(6) Sr 0.2500(6)
5(1)
Site occ.
U(eq)
4(1)
0.2379(1)
x
0.2376(1)
1/4
1/4
y
1/4
1/4
z
Site occ.
U(eq)
Nd 0.976(2)
4(1)
4(1)
x
0
1/4
0
1/4
y
z
0.0120(1)
Nd 0.958(2) Ca 0.042(2)
0.0122(1)
Site occ.
U(eq)
4(1)
1/4
4(1)
1/4
1/4
0
x
y
1/4
z
0
Nd 0.930(2) Ca 0.062(2)
4(1)
Site occ.
U(eq)
4(1)
x
0
1/4
y
z
1/4
0.025(4)
4(1)
Site occ.
U(eq)
Se1
Se2
Se3
Cl1
Cl2
Cl3
Cl4
O1
x
0.1105(1)
0.3631(1)
0.1396(1)
4(1)
0.1109(1)
0.3628(1)
0.1392(1)
5(1)
y
z
U(eq)
x
0.3777(1)
0.3770(1)
0.1011(1)
4(1)
0.3777(1)
0.3761(1)
0.1012(1)
4(1)
y
z
U(eq)
x
0.6490(1)
0.3740(1)
0.1277(1)
4(1)
0.6492(1)
0.3733(1)
0.1277(1)
4(1)
y
z
U(eq)
x
0
0
y
ꢁ0.0029(2)
1/4
12(1)
ꢁ0.0037(2)
1/4
17(1)
z
U(eq)
x
0
0
y
0
0
z
0
20(1)
0
23(1)
U(eq)
x
1/4
0
1/4
0
y
z
0.2370(2)
9(1)
1/4
0.2373(2)
14(1)
1/4
U(eq)
x
y
0
0
z
0.0172(2)
11(1)
0.0168(2)
15(1)
U(eq)
x
0.0042(4)
0.3503(3)
0.1235(3)
5(1)
0.1381(3)
0.2720(3)
0.1115(3)
7(1)
y
z
U(eq)
O2
x
y
0.1373(4)
0.2713(3)
0.6205(3)
0.3208(3)

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Table 2 (continued )
Atom
Parameter
Ca170.14Nd9.9770.14(SeO3)12Cl8 93 K
Sr170.01Nd1070.01(SeO3)12Cl8 93K
z
0.1119(4)
5(1)
0.0429(3)
6(1)
U(eq)
x
O3
O4
O5
O6
O7
O8
O9
0.6210(3)
0.3212(3)
0.0422(3)
4(1)
0.1273(3)
0.3503(4)
0.2446(3)
7(1)
y
z
U(eq)
x
0.3752(3)
0.3490(3)
ꢁ0.0041(3)
5(1)
0.4620(3)
0.3220(3)
0.1257(3)
7(1)
y
z
U(eq)
x
0.1267(3)
0.3508(4)
0.2449(4)
7(1)
0.3754(3)
0.3480(4)
ꢁ0.0035(3)
7(1)
y
z
U(eq)
x
0.7541(4)
0.3464(3)
0.1255(3)
4(1)
0.2928(3)
0.3227(3)
0.1291(3)
5(1)
y
z
U(eq)
x
0.6243(3)
0.3205(3)
0.2126(4)
5(1)
0.6246(3)
0.3199(3)
0.2122(3)
6(1)
y
z
U(eq)
x
0.4623(4)
0.3220(3)
0.1254(3)
6(1)
0.7535(3)
0.3451(4)
0.1254(2)
7(1)
y
z
U(eq)
x
0.2926(4)
0.3230(3)
0.1288(3)
5(1)
0.0057(3)
0.3498(4)
0.1231(3)
8(1)
y
z
U(eq)
Karlsruhe, 76344 Eggenstein-Leopoldshafen, Germany
(fax: (+49)7247 808 666; e-mail: crysdata@fiz-karlsruhe.
de, http://www.fiz-karlsruhe.de/request_for_deposited_data.
html) on quoting the appropriate CSD numbers 418190
for CaNd10(SeO3)12Cl8, and 418191 for SrNd10(SeO3)12Cl8.
Some important interatomic distances for the studied
compounds are presented in Table 3.
Nd2–Cl bonds. The only Nd site which forms Nd–Cl bonds
is the Nd2 site, where the majority of the Ca/Sr ions
are located. It should be noted that in the compounds
under discussion the O2ꢁ is a rather strong Lewis base
(Sb-norm ¼ 0.50 v.u.) compared to weaker halides
(Sb–norm ¼ 0.17 for Clꢁ and 0.05 for Brꢁ) [19]. In
accordance with Brown’s valence matching principle RE
cations which are the stronger Lewis acids (for example,
Sa ¼ 0.4 v.u. for Nd3+) will tend to bond to the O2ꢁ
anions, and alkali and AE metals as the weaker Lewis acids
(Sa ¼ 0.27 and 0.24 for Ca2+ and Sr2+ accordingly) will
tend to bond with halides.
The neodymium atoms in positions Nd1, Nd3–Nd5 have
only oxygen neighbors (Table 3). Coordination surround-
ings for Nd1 and Nd3 are square antiprisms. In the cases of
Nd1 and Nd3 such antiprisms are capped by two
additional oxygen atoms. [Nd3O8] and [Nd5O10] polyhedra
share their O2–O6–O9 sides and form infinite chains along
the c-axis. In the perpendicular direction these chains are
connected by [Nd1O8] antiprisms via O7–O7 edges and by
[Nd4O10] polyhedra via a common O2–O3–O4 face. As the
result of such polyhedral linkage a friable metal-oxygen
slab is formed (Fig. 2) perpendicular to the [010] direction
of structure. Inside this slab, in case of CaNd10(SeO3)12
Cl8,one additional, partly occupied (about 2.5%) site
3. Results and discussion
Our experiments show that CaNd10(SeO3)12Cl8 and
SrNd10(SeO3)12Cl8 have the same structure (Tables 1–3).
The unit cell for CaNd10(SeO3)12Cl8 is presented in Fig. 1.
There are five Nd positions in the structures. Alkaline
earth atoms are distributed on the Nd sites in an ordered
manner. In the Sr compound all Sr ions are in the Nd2
position, where they are about 1/4 of full occupancy. In the
Ca compound most of the calcium ions are in the Nd2 site
too, but some of them are in sites of Nd4 and Nd5. The
explanation of this phenomenon may be in the difference in
2+
2+
ionic radii of Nd3+ (1.109 A), Ca
˚
(1.12 A) and Sr
˚
2+
˚
(1.26 A) [18]. From this point of view Ca may more
, as was observed for
satisfactorily substitute Nd3+
CaNd10(SeO3)12Cl8. Another possible reason for the
agglomeration of Ca/Sr on the Nd2 site could be the

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3023
Table 3
Bond lengths (A) for MNd10(SeO3)12Cl8 (M ¼ Ca, Sr)
˚
CaNd10(SeO3)12Cl
bond
93 K
distance
SrNd10(SeO3)12Cl
bond
93 K
distance
Nd1–O7 ꢂ 4
Nd1–O8 ꢂ 4
Nd2–O1
2.368(5)
2.394(5)
2.347(6)
2.368(6)
2.404(6)
2.422(6)
2.9262(17)
2.9550(15)
2.9853(19)
3.0422(6)
2.442(5)
2.468(6)
2.544(5)
2.578(5)
2.699(5)
2.412(5)
2.471(6)
2.563(5)
2.603(5)
2.678(6)
2.453(5)
2.478(5)
2.510(6)
2.588(5)
2.605(5)
2.644(5)
2.644(4)
2.644(5)
1.684(6)
1.691(6)
1.709(6)
1.674(6)
1.682(6)
1.719(6)
1.671(6)
1.684(6)
1.708(6)
Nd1–O7 ꢂ 4
Nd1–O4 ꢂ 4
Nd2–O9
2.396(5)
2.418(5)
2.397(6)
2.403(6)
2.451(6)
2.481(6)
2.9620(18)
2.9859(17)
3.025(2)
3.0707(6)
2.463(5)
2.481(6)
2.569(5)
2.592(5)
2.724(5)
2.436(5)
2.487(6)
2.595(5)
2.619(5)
2.714(5)
2.487(5)
2.506(5)
2.526(5)
2.598(5)
2.626(5)
Nd2–O5
Nd2–O4
Nd2–O3
Nd2–O5
Nd2–O6
Nd2–Cl3
Nd2–O8
Nd2–Cl3
Nd2–Cl1
Nd2–Cl4
Nd2–Cl2
Nd2–Cl1
Nd2–Cl4
Nd2–Cl2
Nd3–O9 ꢂ 2
Nd3–O5 ꢂ 2
Nd3–O7 ꢂ 2
Nd3–O6 ꢂ 2
Nd3–O2 ꢂ 2
Nd4–O3 ꢂ 2
Nd4–O1 ꢂ 2
Nd4–O8 ꢂ 2
Nd4–O4 ꢂ 2
Nd4–O2 ꢂ 2
Nd5–O3 ꢂ 2
Nd5–O9 ꢂ 2
Nd5–O2 ꢂ 2
Nd5–O6 ꢂ 2
Nd5–O4 ꢂ 2
Nd6–O1 ꢂ 4
Nd6–O5 ꢂ 2
Nd6–O5 ꢂ 2
Se1–O5
Nd3–O6 ꢂ 2
Nd3–O3 ꢂ 2
Nd3–O7 ꢂ 2
Nd3–O8 ꢂ 2
Nd3–O1 ꢂ 2
Nd4–O2 ꢂ 2
Nd4–O9 ꢂ 2
Nd4–O4 ꢂ 2
Nd4–O5 ꢂ 2
Nd4–O1 ꢂ 2
Nd5–O2 ꢂ 2
Nd5–O6 ꢂ 2
Nd5–O1 ꢂ 2
Nd5–O8 ꢂ 2
Nd5–O5 ꢂ 2
Fig. 1. Unit cell for CaNd10(SeO3)12Cl8. Nd2 positions are marked
Thermal ellipsoids are drawn with 95% probability.
of MNd10(SeO3)12Cl8 (M ¼ Ca, Sr) may be considered as a
3D-structure with an open framework (Fig. 3).
It is easy to see that the crystal structures of the new
compounds described above are close to the known phases
CsSm21(SeO3)24Br16 (Z ¼ 2) or Bi10.67(SeO3)12Br8 (Z ¼ 4)
[8]. In the crystal structure of CsSm21(SeO3)24Br16 cesium
atoms are distributed in one of the Sm sites (Sm5). As in
the Ca(Sr) compounds the basis of the CsSm21(SeO3)24Br16
structure is a samarium–oxygen layer formed by Sm1–
Sm4 and linked by SeO3E groups. Sm5 atoms (positions
of which are 1/8 filled by Cs) have 4O+4Cl anti-
prismatic surrounding. These Sm5O4Cl4 polyhedra connect
different Sm–O layers by sharing oxygen and chloride
vertices.
Another example of a related structure is the compound
CoNd10(SeO3)12Cl8 [15]. Cobalt has a smaller coordination
number 6 (CoO4Cl2) in this compound and occupies
a different site from neodymium. For this reason the
crystal structure of CoNd10(SeO3)12Cl8 is more distorted
(to monoclinic) (P2/c, a ¼ 15.699(2), b ¼ 15.700(2), c ¼
19.171(2), b ¼ 113.995(5)1).
Se1–O9
Se1–O3
Se1–O1
Se2–O4
Se2–O6
Se2–O5
Se3–O7
Se3–O2
Se3–O8
1.695(5)
1.703(5)
1.714(6)
1.681(6)
1.695(5)
1.731(5)
1.681(5)
1.692(5)
1.720(6)
Se1–O1
Se1–O2
Se2–O8
Se2–O9
Se2–O4
Se3–O7
Se3–O3
Se3–O6
exists, Nd6. The Nd6 environment is a cube constructed by
eight oxygen atoms (4 O5 and 4 O1 at distances about
˚
2.64 A (Table 3)). The selenium atoms are situated in
the hollows of this metal-oxygen slab and connected with
three oxygens of it (Fig. 2). The SeO3 pyramids may be
described as classical SeO3E c-tetrahedron with E-lone
electron pair. As may be seen from Fig. 2 the SeO3E
groups are situated in such a way that E pairs should be
directed into the interlayer space. The Se–O bonds play a
role as additional linkage of metal-oxygen slabs (Fig. 1).
Finally Ca(Sr)–Nd–Se–O form layers with composition
[M11(SeO3)12]8+ between which layers of chloride anions
are situated. Nd2 is situated at the border of the
[M11(SeO3)12]8+ block and has a distorted square antipris-
matic environment, with Cl atoms in one bigger base and
oxygen in another smaller one (Table. 3). Each Nd2O4Cl4
antiprism shares one Cl–Cl edge with another antiprism
from a different [M11(SeO3)12]8+ block. Thus the structure
The variety of alkali metal REE selenite-halogenides
(Cs3La11(SeO3)12Cl12 [13], K7Sm11(SeO3)12Cl16 and
Cs7Pr11(SeO3)12Cl16 [14] shows the trend that increasing
the alkali metal content in these compounds leads to
formation of ordering in the metal and REE crystal-
lographic sites. The geometry of the unit cell may differ,
but the principle of structural architecture is the same.
Metal-oxygen layers with composition [M11(SeO3)12]n+ are
separated by different layers of halogenide anions or
‘CsCl’-like type. The difference is only in the linkage of

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3024
Fig. 2. Neodymium polyhedral layer with SeO3 groups in the structure of CaNd10(SeO3)12Cl8. Nd6 sites are marked as gray balls.
Fig. 3. Representation of the crystal structure of CaNd10(SeO3)12Cl8 with Nd-polyhedra revealing the 3D-framework.
such structure blocks into a 3D-framework. Several
examples of [M11(SeO3)12]n+ block linkage are presented
in Fig. 4.
The observations listed above prompt us to suggest that
alkaline-earth metal REE selenite-halogenides may form
phases with much bigger alkaline-earth content and with

ARTICLE IN PRESS
P.S. Berdonosov et al. / Journal of Solid State Chemistry 180 (2007) 3019–3025
3025
n+
Fig. 4. Different type of [M11(SeO3)12
]
block linkage in (a) Cs7Pr11(SeO3)12Cl16 [14], (b) K7Sm11(SeO3)12Cl16 [14], Rb6LiLn11(SeO3)12Cl12 [11,12], (c)
MNd10(SeO3)12Cl8 (M ¼ Ca, Sr), CsSm21(SeO3)24Br16, Bi10.67(SeO3)12Br8 [8], (d) Cs3La11(SeO3)12Cl16 [13] All unit cells are shown in a direction
perpendicular the longest cell parameter.
ordering in metal sites. The search for such compounds is
now in progress.
[5] H. Oppermann, H. Dao Quoc, M. Zhang-PreXe, P. Schmidt, B.A.
Popovkin, P.S. Berdonosov, V.A. Dolgikh, Z. Anorg, Allg. Chem.
628 (2002) 891–895.
[6] M.S. Wickleder, Z. Naturforsch. 57b (2002) 1414–1418.
[7] M.S. Wickleder, M. Ben, Z. Hamida, Anorg. Allg. Chem. 629 (2003)
556–562.
Acknowledgments
This work has been carried out under funding of the
Russian Foundation for Basic Research, Grant # 06-03
32134 and PSB thanks INTAS YSF # 05-109-4474. We
thank Prof. Alex M. Z. Slawin, Mr. Ross Blackley and Dr.
A. G. Veresov for assistance in experimental data collec-
tion.
[8] M. Ruck, P. Schmidt, Z. Anorg, Allg. Chem. 629 (2003) 2133–2143.
[9] J. Wontcheu, T. Schleid, J Solid State Chem. 171 (2003) 429–433.
[10] T. Schleid, J. Wontcheu, J. Alloys Compds. 418 (2006) 45–52.
[11] C. Lipp, T. Schleid, Z. Kristallogr. Suppl. 22 (2005) 141.
[12] C. Lipp, T. Schleid, Z. Anorg, Allg. Chem. 632 (2006) 2226–2231.
[13] P.S. Berdonosov, O.S. Oleneva, V.A. Dolgikh, Acta Crystallogr. E 62
(2006) i29–i31.
[14] P.S. Berdonosov, V.A. Dolgikh, P. Schmidt., M. Ruck. Complex
chloride-selenites of rare earthes – a family of new phases in: IV
National Crystal Chemical Conference Chernogolovka 26–30 June
2006 Book of abstracts, pp.192–193.
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