Non-centrosymmetric rubidium rare-earth nitrates Rb2IHT(NO 3)54H2O: Crystal growth and optical properties

Article abstract of DOI:10.1002/zaac.200801395

Large single crystals of optical quality of the isomorphic, non-centrosymmetric, monoclinic (space group Cc) compounds Rb ₂La(NO₃).4H₂O and Rb₂Ce(NO ₃)., ? 4H₂O were grown. The determinatio

Full text of DOI:10.1002/zaac.200801395

ARTICLE
DOI: 10.1002/zaac.200801395
Non-centrosymmetric Rubidium Rare-earth Nitrates Rb RE(NO ) ·4H O:
2
3 5
2
Crystal Growth and Optical Properties
[a]
[a]
[a]
Ladislav Bohat y´ ,* Peter Held, and Petra Becker
Dedicated to Professor Gerd Meyer on the Occasion of His 60th Birthday
Keywords: Rubidium rare earth nitrate; Crystal growth; Non-centrosymmetric crystal; Refractive indices; SHG phase
matching
Abstract. Large single crystals of optical quality of the isomorphic,
non-centrosymmetric, monoclinic (space group Cc) compounds
monic generation. Type I phase matching conditions can be real-
ized in both crystals for a wide frequency range. Our X-ray struc-
Rb
2
La(NO
3
)
5
·4H
2
O and Rb
2
Ce(NO
3
)
5
·4H
2
O were grown. The ture
determination
of
Rb
2
Nd(NO
3
)
5
·4H
2
O
and
determination of precise refractive indices and their dispersion in
the wavelength region 0.365Ϫ1.083 µm allowed a detailed analysis
of phase matching conditions for nonlinear optical second har-
Rb
2
Pr(NO ·4H O shows that both compounds are isomorphic
3
)
5
2
to the lanthanum and cerium compounds.
Introduction
At this point the question arises, whether the rubidium
rare earth nitrates tetrahydrates are isomorphous with the
corresponding ammonium compounds (and are therefore
centrosymmetric) or the above cited description [3, 4] in the
polar space group Cc is correct. Using small crystals of
Rb RE(NO ) ·4H O (RE ϭ La, Ce), which were synthe-
Among the alkali rare earth nitrates, members of the
family of the polar orthorhombic compounds of type
K RE(NO ) ·2H O (with RE ϭ LaϪNd) turned out to be
2
3 5
2
attractive crystals for efficient nonlinear optical frequency
conversion through second harmonic generation (SHG)
2
3 5
2
sized in a first step of our investigation, we could detect
unambiguously piezoelectricity of the crystals as well as the
generation of second harmonic of laser light, thus giving a
strong proof of the non-centrosymmetry of the rubidium
compounds. These first results encouraged the growth of
large single crystals of the colorless compounds
Rb La(NO ) ·4H O and Rb Ce(NO ) ·4H O for linear
[
1, 2]. Whereas isomorphic compounds with rubidium are
unknown, tetrahydrates Rb RE(NO ) ·4H O that crys-
2
3 5
2
tallize with monoclinic symmetry Cc were described for
RE ϭ La and Ce by [3, 4]. Already in 1907, these com-
pounds had been reported first by Wyrouboff [5], who gave
a detailed morphological description and pointed out their
isomorphism to the corresponding ammonium compounds
2
3 5
2
2
3 5
2
and nonlinear optical investigations. In addition, we studied
the crystal structure of the corresponding praseodymium
and neodymium compound.
(
NH ) RE(NO ) ·4H O (RE ϭ LaϪNd) [6Ϫ10]. The com-
4 2 3 5 2
pounds were reported with (centrosymmetric) monoclinic-
prismatic symmetry that was maintained for the ammonium
compounds in later X-ray structure determinations
Results and Discussion
[
11Ϫ13]. Wyrouboff [5] also reported on a probably iso-
morphic rubidium “didymium” compound, the iso-
morphism of Rb Pr(NO ) ·4H O and Rb Nd(NO ) ·
Crystal Structure
2
3 5
2
2
3 5
4
H O with the lanthanum and cerium compounds was
Our crystal structure analysis reveals that Rb Nd(NO ) ·
2
2
3 5
stated also by [14], however, no structure determination of 4H O and Rb Pr(NO ) ·4H O are isomorphic to the corre-
2
2
3 5
2
the praseodymium and neodymium compounds is given in sponding lanthanum and cerium compounds [3, 4], with
literature.
space group symmetry Cc and lattice parameters as summa-
rized in Table 1. The prominent structural unit is a distorted
icosahedral coordination polyhedron of the rare earth
[
REO ], where ten oxygen ligands belong to five biden-
12
*
Prof. Dr. L. Bohaty´
tately coordinating nitrate groups and the remaining two
oxygen ligands are oxygen atoms of water molecules,
leading to a structural building block [RE(NO ) (H O) ]
see Figure 1. The arrangement of the [NO ] groups around
Fax: ϩ49-221-470-4963
E-Mail: ladislav.bohaty@uni-koeln.de
[
a] Institut für Kristallographie
2Ϫ
,
3
5
2
2
Universität zu Köln
Zülpicher Str. 49 b
3
50674 Köln, Germany
the central rare earth cation gives an approximately
2236
 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2009, 635, 2236Ϫ2241

Non-centrosymmetric rubidium rare-earth nitrates Rb
2
RE(NO
RE(NO ·4H
Ndc)
3 5 2
) ·4H O
Table 1. Crystal structure data of monoclinic Rb
with RE ϭ La Ϫ Nd.
2
3
)
5
2
O
Laa)
Ceb)
Prc)
˚
a /A
11.092(4)
8.984(2)
17.863(6)
100.85(1)
1748.2
4
11.050(1)
8.977(1)
17.859(2)
100.877(9)
1739.6(2)
4
11.0223(8)
8.9691(5)
17.861(2)
100.929(9)
1733.7(3)
4
11.0011(6)
8.9601(3)
17.840(3)
100.966(7)
1726.3(3)
4
˚
b /A
˚
c /A
β /°
˚
3
V /A
Z
Ϫ3
ρ /g· cm
2.49
2.648
2.659
2.683
a) Vigdorchik et al., 1992 [3]; b) Audebrand et al., 1996 [4]; c) this
paper.
radial paddle wheel-like geometry, which was also described
for Cs La(NO ) ·2H O [15] and for the ammonium
2
3 5
2
compounds (NH ) RE(NO ) ·4H O (RE
ϭ
La, Ce,
4
2
3 5
2
Nd) [11Ϫ13] and (NH ) La(NO ) ·3H O [11]. The
4
2
3 5
2
[
RE(NO ) (H O) ] groups are arranged in layers parallel
3 5 2 2
(001) that alternate with layers of rubidium cations and
H O along the c-axis. The resulting sheet-like structure
corresponds to a distinct cleavage of the crystals parallel
to (001).
2
Figure 1. Coordination polyhedron [Nd(NO
3
)
5
(H
2
O)
2
]
in
Rb Nd(NO ·4H O. Non hydrogen atoms are shown as 50 % pro-
2
3
)
5
2
bability displacement ellipsoids and hydrogen atoms as spheres
with arbitrary radius for clarity.
In the nonlinear optically attractive potassium com-
pounds of type K RE(NO ) ·2H O (with RE ϭ La Ϫ Nd)
2
3 5
2
a similar structural building block [RE(NO ) (H O) ] is pounds Rb RE(NO ) ·4H O (with RE ϭ La Ϫ Nd), and
3
5
2
2
2
3 5
2
present. Here, however, the arrangement of the [NO3] no radial paddle wheel-like geometry but a pronounced
groups differs markedly from that in the rubidium com- polar arrangement is found [16].
Figure 2. (a) Typical morphology of grown crystals of Rb
2
La(NO
} are indicated. (b) Example of a grown crystal of Rb
holder. (c) Example of a grown crystal of Rb Ce(NO ·4H O. The region of the seed crystal is clearly visible in both crystals. Crystals
shown in (b) and (c) are approximately of the same size.
3
)
5
·4H
2
O and Rb
2
Ce(NO
3 5 2
) ·4H O; face indices and the crystallographic
Ǟ
reference system {a
i
2
La(NO
3
)
5
·4H O, fixed with platinum wire to the seed crystal
2
2
3
)
5
2
Z. Anorg. Allg. Chem. 2009, 2236Ϫ2241
 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.zaac.wiley-vch.de
2237

L. Bohat y´ , P. Held, P. Becker
ARTICLE
Crystal Growth
From our growth experiments large single crystals
of dimensions up to 4 ϫ 4 ϫ 3 cm and a mass of
5
0Ϫ75 g for both compounds, Rb La(NO ) ·4H O and
2 3 5 2
Rb Ce(NO ) ·4H O, were obtained, see Figure 2b and Fig-
2
3 5
2
ure 2c. In the progress of the growth process, the disturb-
ances in the region around the initial seed crystal, which are
visible in Figure 2b and Figure 2c, vanished, and crystals of
high optical quality, which allow the measurement of high-
precision refractive indices, resulted. The morphology of
¯
the crystals is dominated by the pedions (001) and (001)
¯
and domes {110} and {110}. Additionally, the pedions
¯ ¯ ¯ ¯
¯
(
{
100), (100), (101), (101) and domes {111}, {111}, {112},
¯
¯
¯ ¯
¯ ¯
112}, {111}, {111} and {112} occur, see Figure 2a. The
well-developed faces of the crystals were used as reference
for the preparation of oriented samples. Crystal physical
properties reported in this work are related to a Cartesian
Ǟ
system {e } that is defined with respect to the crystallo-
i
Ǟ
Ǟ
Ǟ
Ǟ
Ǟ
Ǟ
Ǟ
Ǟ
graphic system {a } as follows: e ʈa , e ʈa , e ϭ e ϫ e .
i
2
2
3
3
1
2
3
Ǟ
Ǟ
In our crystals positive directions of e and e correspond
1
3
with a positive sign of the piezoelectric constant d111 and
d333, respectively.
Optical Properties
Refractive index data were measured at 11 discrete wave-
lengths and were corrected with the refractive index of air
(
see Experimental Section). All data given here correspond
Figure 3. Principal refractive indices and their dispersion, together
to the corrected values. A modified Sellmeier equation of
the type
with unpolarized absorption spectra (insets) of crystals of
Rb
lower panel). Symbols indicate experimental refractive index data,
lines indicate the fitted Sellmeier functions.
2 3 5 2 2 3 5 2
La(NO ) ·4H O (upper panel) and of Rb Ce(NO ) ·4H O
(
was used to fit the refractive indices. In Figure 3, the
principal refractive indices and their dispersion, together
with the Sellmeier functions are illustrated, the Sell- 4H
Crystals of Rb
O are biaxial negative with a small birefringence
Ϫ n0
Η. In monoclinic crystals the orientation of
range of the crystals extends from approx. 0.315 µm for the directions where the principal refractive indices of the
Rb La(NO ) ·4H O and approx. 0.355 µm
for crystals are found, i.e. the orientation of the principal axes
Rb Ce(NO ) ·4H O in the UV (50 % transmission) to of the optical indicatrix denoted by { e } in this work, is
La(NO ) ·4H O and Rb Ce(NO ) ·
2
3 5 2 2 3 5
2
meier coefficients are given in Table 2. The transparency ∆n ϭ Ηn0
1
2
2
3 5
3 5
2
Ǟ0
2
2
i
Ǟ0
Ǟ0
Ǟ0
about 1.40 µm in the infrared range, where first absorption only fixed for e2 whereas the orientation of e1 and e3
bands occur for both compounds (see insets of Figure 3).
varies within the plane (010) with wavelength of light. This
wavelength-dependent dispersion of the orientation is given
Ǟ
Ǟ
here as the angle Φ between the axis e (ʈa ) and the princi-
Table 2. Sellmeier coefficients for crystals of Rb
and Rb Ce(NO ·4H O; the wavelength in the Sellmeier equation pal axis e3 of the optical indicatrix (i.e. the extinction
is in µm (ζ is the sum of the squares of the residuals of the fit).
2
La(NO
3
)
5
·4H
2
O
3
3
Ǟ0
2
3
)
5
2
2
Ǟ
angle of the crystal with respect to the a -axis for a light
3
Ǟ
D
1
D
2
D
3
D
4
ζ2
wave propagation along e ). In Figure 4, the mutual
2
Ǟ
Rb
2
La(NO
3
)
5
·4H
2
O
orientation of the crystallographic reference system {a },
i
Ǟ
0
1
0
2
0
3
Ϫ11
Ϫ10
Ϫ11
the crystal physical Cartesian system {e } and the system
n
n
n
2.27643(8) 0.01633(2) 0.0308(1) 0.00906(7) 6.1 ϫ 10
2.2732(2) 0.01668(6) 0.0304(3) 0.0083(2) 3.1 ϫ 10
2.20288(6) 0.01458(2) 0.0300(1) 0.00663(5) 3.4 ϫ 10
i
Ǟ0
of principal axes of the optical indicatrix { e } is scetched
i
for the title crystals of this work. The wavelength-dependent
Ǟ0
1
Ǟ0
3
Rb
2
Ce(NO
3
)
5
·4H
2
O
¯
rotation of the principal axes e and e around the 2 axis
0
Ϫ9
n
n
n
1
0
2
0
3
2.2868(4) 0.0165(1) 0.0341(5) 0.0095(3) 1.3 ϫ 10
2.2878(6) 0.0172(2) 0.0348(10) 0.0086(4) 1.4 ϫ 10
2.2145(3) 0.01493(8) 0.0322(4) 0.0071(2) 8.0 ϫ 10
is illustrated by the wavelength dispersion of the angle Φ in
Figure 5. Observed with white light this effect is visible on
Ϫ9
Ϫ10
(010) plates of the crystals as bluish or reddish colors when
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2 3 5 2
Non-centrosymmetric rubidium rare-earth nitrates Rb RE(NO ) ·4H O
the crystals are slightly rotated off the position of maximum
extinction in both directions between crossed polarizers.
The angle between the optic axes (named 2V in the follow-
α
ing, see Figure 4) of Rb La(NO ) ·4H O increases with
2
3 5
2
wavelength in the visible and slightly decreases again in
the IR region (see Figure 6), the plane of the optic axes is
Ǟ0 Ǟ0
(
e , e ), i.e. (010). For Rb Ce(NO ) ·4H O, 2V de-
1 3 2 3 5 2 α
creases in the visible and slightly increases again inǞth0eǞI0R
see Figure 6), here, the plane of the optic axes is ( e , e ),
(
2
3
i.e. the plane is rotated by 90° compared to that in
Rb La(NO ) ·4H O, as it is visualized in Figure 4. As a
2
3 5
2
consequence of this result, the possibility to design a mono-
clinic crystal with optically uniaxial behavior within a cer-
tain wavelength range by the synthesis of mixed crystals
Rb (La,Ce)(NO ) ·4H O of appropriate ratio of La:Ce Figure 5. Wavelength dispersion of the orientation angle Φ
2
3 5
2
Ǟ0 Ǟ
appears.
(ϭ ѯ( e ,a ) for crystals of Rb La(NO ) ·4H O and
3
3
2
3 5
2
Rb
2
Ce(NO
3
)
5
·4H
2
O. Symbols: calculated from experimental data;
lines: calculated from Sellmeier coefficients.
Figure 6. Wavelength dispersion of the acute angle 2V
α
between the
·4H O.
optic axes of Rb
2
La(NO
3
)
5
·4H
2
O
and Rb
2
Ce(NO
3
)
5
2
Symbols: calculated from experimental data; lines: calculated from
Sellmeier coefficients.
cesses of both types, type I phase matching (with ss-f inter-
action; s ϭ slow wave, f ϭ fast wave) and type II phase
matching (with sf-f interaction) can be realized in both crys-
tals, Rb La(NO ) ·4H O and Rb Ce(NO ) ·4H O. How-
2
3 5
2
2
3 5
2
ever, type II phase matching is limited to the IR region
where absorption already occurs in both crystals. Phase
matching loci for several wavelengths of the fundamental
Figure 4. Mutual orientation of the crystallographic reference
Ǟ
Ǟ
wave are presented as Hobden plots (i.e. stereographic
system {a
system of principal axes of the optical indicatrix { e
of Rb La(NO ·4H O and Rb Ce(NO ·4H O.
i
}, the crystal physical Cartesian system {e
i
} and the
Ǟ0
Ǟ0
projection using the reference system { e } [17]) for both
i
i
} for crystals
crystals in Figure 7. Non-critical phase matching type I is
2
3
)
5
2
2
3
)
5
2
possible for a wavelength of 0.876 µm of the fundamental
Ǟ
Ǟ0
wave with wave normal k parallel to e and at 0.889 µm
2
The high-precision refractive indices (with error less than
Ǟ
k
Ǟ0
1
Ϫ4
for
parallel to
e
in Rb La(NO ) ·4H O. In
2 3 5 2
1
ϫ 10 ) and their dispersion allow an analysis of con-
Rb Ce(NO ) ·4H O, non-critical phase matching type I
2
3 5
2
ditions for phase matching of different nonlinear optical
frequency conversion processes. Herein, we focus in can be realized at 0.887 µm for k parallel to e
Ǟ
Ǟ0
1
and at
Ǟ
Ǟ0
particular on the conditions for collinear second harmonic 0.902 µm for k parallel to e . The point group symmetry
2
0
0
generation (SHG). Based on the birefringence Ηn Ϫ n Η and m of the crystals allows non-zero effective coefficients
1
3
0
0
SHG
eff
Ηn Ϫ n Η, respectively, collinearly phase matched SHG pro-
d
of the SHG tensor for both directions of non-critical
2
3
Z. Anorg. Allg. Chem. 2009, 2236Ϫ2241
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2239

L. Bohat y´ , P. Held, P. Becker
ARTICLE
SHG
phase matching type I in the crystals, e.g. d311 for ing new nonlinear optical materials. In a forthcoming work
Ǟ0
Ǟ0
1
SHG
SHG
the nonlinear optical susceptibility tensor [dijk ] will be de-
incidence along e2 and d322 for incidence along e . The
termined on the example of the lanthanum compound. An
extension of the isomorphic series to a samarium com-
pound seems highly improbable, to the best of our know-
ledge no crystal structure is known with samarium in duo-
decimal oxygen coordination [SmO ]. Indeed, for the sys-
difference in wavelength for non-critical phase matching
between Rb La(NO ) ·4H O and Rb Ce(NO ) ·4H O of
2
3 5
2
2
3 5
2
Ǟ0
26 nm for incidence along e2 shows that by synthesis of
mixed crystals Rb (La,Ce)(NO ) ·4H O the wavelength for
2
3 5
2
12
non-critical phase matching can be fine-tuned to a desired
value within this range.
tem RbNO /Sm(NO ) /H O only a dihydrate of compo-
3
3 3
2
sition Rb Sm(NO ) ·2H O (probably triclinic) is reported
2
3 5
2
in literature [18], its crystal structure, however, is not given.
Experimental Section
Crystal Growth
Large single crystals of Rb
O were grown from saturated aqueous solutions with a stoi-
chiometric ratio of the constituents (2 RbNO ϩ 1 La(NO or
Ce(NO ) and a small addition (ca. 5 %) of HNO . Lanthanum
nitrate was synthesized by dissolving La (Chempur, 99.99 %)
in nitric acid, the cerium nitrate was purchased as hexahydrate,
Ce(NO ·6 H O (Chempur, 99.9 %) and commercially available
2 3 5 2 2 3 5
La(NO ) ·4H O and Rb Ce(NO ) ·
4H
2
3
3 3
)
1
3
)
3
3
2
O
3
3
)
3
2
rubidium nitrate (CERAC Inc., 99,9 %) was used. The growth pro-
cess was performed for both compounds in 3 L crystallization ves-
sels, held at constant temperature of 41 °C, by slow controlled evap-
oration of the solvent. The evaporation rate was adjusted to achieve
Ϫ1
a linear growth rate of approximately 0.3 mm·day . Seed crystals
were suspended on platinum wire. In our experiments a growth
period of 10Ϫ16 weeks was typically applied.
Small crystals of Rb
suitable for X-ray structure determination were synthesized at
0 °C from aqueous solutions of the nitrates RbNO and
RE(NO (RE ϭ Nd, Pr) in stoichiometric ratio 2 Rb : 1 RE with
ca. 5 % HNO added. The solutions of the rare earth nitrates were
prepared by dissolving of Nd (Alfa, 99.9 %) and Pr 11 (Alfa
Aesar, 99.9 %), respectively, in nitric acid using a small surplus of
HNO . All four compounds Rb RE(NO ·4H O are sensitive to
2 3 5 2 2 3 5 2
Nd(NO ) ·4H O and Rb Pr(NO ) ·4H O
2
3
3 3
)
3
2
O
3
6
O
3
2
3
)
5
2
humidity, especially the praseodymium and neodymium com-
pounds.
Figure 7. Stereographic projections of phase matching loci for colli-
near second harmonic generation (Hobden plots) for different fun-
Optical Properties
damental wavelengths in Rb
2 3 5 2
La(NO ) ·4H O (upper panel) and
Crystals of monoclinic symmetry, such as Rb
Rb Ce(NO ·4H O, possess three principal refractive indices
. They were determined by the prism method and normal
incidence using two prisms with incidence face (010) (prism I) and
2 3 5 2
La(NO ) ·4H O and
Rb Ce(NO ·4H O (lower panel). Loci of type I phase matching
2
3
)
5
2
are marked in black, for type II phase matching in grey color.
2
3
)
5
2
0
0
0
1 2 3
n ,n ,n
(
001) (prism II), respectively, for each compound. Measurements
0
0
with the prisms I yield n
yield n
1
and n
3
, measurements with prisms II
Conclusions
0
0
0
2
and nЈ with a value between n
1
and n
3
. For both com-
pounds, data were collected at 11 discrete wavelengths in the region
between 0.365 µm and 1.083 µm with a goniometer-spectrometer
system (Möller-Wedel). The measured data were corrected for the
The results of this work prove that the rubidium rare
earth nitrates tetrahydrates Rb RE(NO ) ·4 H O form an
2
3 5
2
isomorphic series of non-centrosymmetric crystals for
RE ϭ La Ϫ Nd. Since the lanthanum and the cerium com-
pounds (that are non-absorbing in the visible spectral
range) can be grown to large single crystals of high quality
corr
meas air
refractive index of air and its dispersion by n
data from [19]. The extinction angle with respect to the edǞge
between the faces (010) and (001), which has the direction of a
was measured on a plate (010) with a polarizing microscope. Unpo-
ϭ n
·n , using
1
,
and allow the realization of phase matched second har- larized absorption spectra were collected with single crystal plates
monic generation, we can qualify these crystals as promis- (010) of both compounds using a Varian Carey 05E equipment.
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2 3 5 2
Non-centrosymmetric rubidium rare-earth nitrates Rb RE(NO ) ·4H O
ence remains unremarkable (∆ρmax ϭ 1.053 e·AϪ3, ∆ρmin
Ϫ1.027 e·A ).
˚
ϭ
Crystal Structure Determination
˚
Ϫ3
2 3 5 2
Rb Pr(NO ) ·4H O: Unit cell parameters of a cube-shaped single
crystal (0.35 ϫ 0.26 ϫ 0.24 mm) were obtained by least-squares
refinement from accurate angular settings of 25 reflection
Further details of the crystal structure investigations are available
from the Fachinformationszentrum Karlsruhe, 76344 Eggen-
stein-Leopoldshafen, Germany on quoting the depository
(20.78° < θ < 23.76°) located and centred on a four-circle dif-
numbers CSD-420181 (Rb
Rb Pr(NO ·4H O), the name of the authors, and citation of
the paper.
2 3 5 2
Nd(NO ) ·4H O) and CSDϪ420187
fractometer. Room temperature intensity data of 10174 reflections
were collected with a EnrafϪNonius MACH3 diffractometer [20]
(
2
3
)
5
2
with ω/2θ scan technique and graphite monochromatized
˚
Mo-K
α
radiation (λ ϭ 0.7107 A) within the full hemisphere
(
Ϫ15 Յ h Յ 15, Ϫ12 Յ k Յ 12, Ϫ25 Յ l Յ 25; 2θ < 30.41°).
Acknowledgement
The authors thank Prof. A. Möller, Institute of Inorganic Chemisty,
Preliminary investigations confirm a lattice centering, therefore
only reflections with h ϩ k ϭ 2n were measured. The data were
averaged to give 5239 unique reflections (Rint ϭ 0.056). Three
standard reflections monitored periodically every 100 reflections
showed no significant variation in position and intensity (max
University of Cologne, for measurement of absorption spectra.
References
3
.72 %). Lorentz, polarisation and empirical absorption correction
Ϫ1
via psi-scan of nine reflections were applied (µ ϭ 8.495 mm
T
space group Cc (No. 9) was proven to be consistent with the sys-
tematic absences in the original intensity data. Refinement was per-
,
[1] C. A. Ebbers, L. D. DeLoach, M. Webb, D. Eimerl, S. P. Vel-
sko, D. A. Keszler, IEEE J. Quantum Electron. 1993, 29,
497Ϫ507.
min ϭ 0.8204, Tmax ϭ 0.9995, F(000) ϭ 1312). The monoclinic
[
2] H. Hellwig, S. Rühle, P. Held, L. Bohat y´ , J. Appl. Crystallogr.
2000, 33, 380Ϫ386.
3] A. G. Vigdorchik, Y. A. Malinovskii, A. G. Dryuchko, V. B.
Kalinin, I. A. Verin, S. Y. Stefanovich, Sov. Phys. Crystallogr.
2
formed using full-matrix least-squares on F with anisotropic dis-
[
placement factors for non-hydrogen atoms, a structure factor
weighting scheme and secondary isotropic extinction. Most of the
non-hydrogen atoms were located using direct methods, remaining
atoms were found in Fourier maps. In difference Fourier synthesis
the strongest peaks corresponded (according to the stereochemical
data) to possible positions of hydrogen and were identified as hy-
1
992, 37, 783Ϫ791.
[
4] N. Audebrand, J. P. Auffr e´ dic, M. Lou e¨ r, N. Guillou, D. Lou e¨ r,
Solid State Ionics 1996, 84, 323Ϫ333.
[5] M. G. Wyrouboff, Bull. Soc. Franc. Min e´ ral. 1907, 30,
299Ϫ323.
drogen atoms. All hydrogen atoms were restrained in length [6] M. C. Marignac, Ann. Chim. Phys. (S e´ r. 4) 1873, 30, 45Ϫ69.
˚
[7] M. H. Dufet, Bull. Soc. Franc. Min e´ ral. 1888, 11, 143Ϫ148.
(
0.95(2) A] and constrained in the isotropic displacement param-
eter (1.2 times Uequiv of the bonded oxygen atom). The anisotropic
refinement of 269 parameters (4055 reflections with I >4σ(I ))
(F ) ϭ 0.0691 and S ϭ 1.048
(∆/σ)max ϭ (∆/σ)min ϭ 0.000). The Flack parameter is equal to
Ϫ0.00(1). The final difference map showed no unusual features
[
[
[
8] E. H. Kraus, Z. Kristallogr. 1901, 34, 397Ϫ431.
9] A. Fock, Z. Kristallogr. 1894, 22, 29Ϫ42.
0
0
10] P. Groth, Chemische Krystallographie, Wilhelm Engelmann,
Leipzig, 1908, vol. 2, pp. 152Ϫ155.
11] B. Eriksson, L. O. Larsson, L. Niinistö, Acta Chem. Scand. A
2
yielded a residual R(F) ϭ 0.0349, R
w
(
[
1982, 36, 465Ϫ470.
˚
Ϫ3
˚
Ϫ3
(∆ρmax ϭ 1.085 e·A , ∆ρmin ϭ Ϫ0.660 e·A ). All calculation [12] G. Meyer, E. Manek, A. Reller, Z. Anorg. Allg. Chem. 1990,
were performed on a DEC 300 AXP and a 786 PC computer using
the WingX [21] and SHELX97 [22] program systems.
591, 77Ϫ86.
[13] M. Najafpour, P. Starynowicz, Acta Crystallogr., Sect. E 2006,
62, i145Ϫi146.
[
[
14] G. Jantsch, S. Wigdorow, Z. Anorg. Chem. 1911, 69, 221Ϫ231.
15] A. G. Vigdorchik, Y. A. Malinovskii, A. G. Dryuchko, Sov.
Phys. Crystallogr. 1990, 35, 823Ϫ825.
2 3 5 2
Rb Nd(NO ) ·4H O: Procedures of the measurement of the
crystal parameter, the data collection and refinement of the
structure are similar to those used in the structure determina-
[
16] P. Held, H. Hellwig, S. Rühle, L. Bohat y´ , J. Appl. Crystallogr.
2000, 33, 372Ϫ379.
tion of Rb
2
Pr(NO
3
)
5
·4H
2
O.
A
suitable single crystal
(
0.36 ϫ 0.28 ϫ 0.27 mm) was carefully selected under a polarizing [17] M. V. Hobden, J. Appl. Phys. 1967, 38, 4365Ϫ4372.
microscope and mounted in a glass capillary. The cell parameters
were obtained by 25 reflection (20.74° < θ < 24.95°). 10139 meas-
ured reflections (within a 2θ range of 30.40°) were averaged to give
[18] Z. K. Odinets, N. A. Sal’nikova, A. K. Molotkin, T. N.
Ivanova, Russ. J. Inorg. Chem. 1989, 34, 467Ϫ470.
[
[
19] B. Edl e´ n, Metrologia 1966, 2, 71Ϫ80.
20] EnrafϪNonius, MACH3 EXPRESS 1989, Delft, The Nether-
lands.
5
222 unique reflections (Rint ϭ 0.049, decay 2.37 %) corrected by
Ϫ1
absorption correction (µ ϭ 8.717 mm , Tmin ϭ 0.7331, Tmax
.9990, F(000) ϭ 1316). The anisotropic refinement of 269 param-
eters (4416 reflections with I >4σ(I )) yielded a residual R(F) ϭ
(F ) ϭ 0.0562 and S ϭ 1.038 ((∆/σ)max ϭ (∆/σ)min
.000). The Flack parameter is equal to Ϫ0.013(9). The final differ-
ϭ
[
21] L. J. Farrugia, J. Appl. Crystallogr. 1999, 32, 837Ϫ838.
0
[22] G. M. Sheldrick, Acta Crystallogr., Sect. A 2008, 64, 112Ϫ122.
0
0
2
0
.0270, R
w
ϭ
Received: December 18, 2008
Published Online: June 10, 2009
0
Z. Anorg. Allg. Chem. 2009, 2236Ϫ2241
 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.zaac.wiley-vch.de
2241