Crystal structures of EuLnCuS3 (Ln = Nd and Sm)1

Article abstract of DOI:10.1134/S0036023612010172

The compound sulfides EuLnCuS₃ (Ln = Nd and Sm) were obtained for the first time. Their crys- tal structures were determined from X-ray powder diffraction data. The crystals of both compounds are orthorhombic (space group Pnma). The compound EuNdCuS₃ is isostructural with BaLaCuS ₃; the unit cell parameters are a = 11.0438(2) ?, b = 4.0660(1) ?, c = 11.4149(4) ?. The compound EuSmCuS₃ is isostruc- tural with Eu₂CuS₃; the unit cell parameters are a = 10.4202(2) ?, b = 3.9701(1) ?, c = 12.8022(2) ?. Pleiades Publishing, Ltd., 2012.

Full text of DOI:10.1134/S0036023612010172

ISSN 0036ꢀ0236, Russian Journal of Inorganic Chemistry, 2012, Vol. 57, No. 1, pp. 79–83. © Pleiades Publishing, Ltd., 2012.
Original Russian Text © A.V. Ruseikina, L.A. Solovyov, M.S. Molokeev, O.V. Andreev, 2012, published in Zhurnal Neorganicheskoi Khimii, 2012, Vol. 57, No. 1, pp. 86–90.
PHYSICAL METHODS
OF INVESTIGATION
Crystal Structures of EuLnCuS3 (Ln = Nd and Sm)1
A. V. Ruseikinaa, L. A. Solovyovb, M. S. Molokeevc, and O. V. Andreeva
a GOU VPO Tyumen State University, Tyumen, Russia
b Institute of Chemistry and Chemical Technology, Siberian Branch, Russian Academy of Sciences, Krasnoyarsk, Russia
c Kirensky Institute of Physics, Siberian Branch, Russian Academy of Sciences, Krasnoyarsk, Russia
Received December 22, 2010
Abstract—The compound sulfides EuLnCuS3 (Ln = Nd and Sm) were obtained for the first time. Their crysꢀ
tal structures were determined from Xꢀray powder diffraction data. The crystals of both compounds are
orthorhombic (space group Pnma). The compound EuNdCuS3 is isostructural with BaLaCuS3; the unit cell
parameters are
tural with Eu2CuS3; the unit cell parameters are
a
= 11.0438(2) Å,
b
= 4.0660(1) Å,
c
= 11.4149(4) Å. The compound EuSmCuS3 is isostrucꢀ
a
= 10.4202(2) Å, = 3.9701(1) Å, = 12.8022(2) Å.
b
c
DOI: 10.1134/S0036023612010172
1
In [1], the compound sulfides EuLnCuS3 (Ln = mine their crystal structures from Xꢀray powder difꢀ
Gd–Lu) have been obtained by solidꢀstate reactions of fraction data.
rareꢀearth metal(III) oxides (Ln2O3) with cupric oxide
(CuO). Stoichiometric mixtures of the starting
reagents were heated in a graphite boat at 1170–1320 K
EXPERIMENTAL
in a flow of a mixture of gaseous CS2 and N2 prepared
by bubbling N2 through liquid СS2 at room temperaꢀ
ture. The synthesis included several steps of grinding
the resulting product. This method proved to be
Cuprous sulfide was prepared from elemental Cu
(special purity grade 11ꢀ4) and elemental S (special
purity grade 15ꢀ3) in sealed evacuated doubleꢀwalled
quartz tubes. The sulfides EuS, Nd2S3, and Sm2S3
were prepared from appropriate oxides (EvOꢀZh,
NOꢀD, and SmOꢀG grades, respectively) in a flow of
Н2S and СS2 at 1300 K [2]. According to Xꢀray powder
diffraction data, the simple sulfides are singleꢀphase
compounds. They have stoichiometric formulas to
within the chemical analysis error. The compound sulꢀ
fides EuLnCuS3 (Ln = Nd and Sm) were obtained by
fusing mixtures of the starting sulfides (EuS : Ln2S3 :
Cu2S = 2 : 1 : 1) in graphite crucibles placed in sealed
evacuated doubleꢀwalled quartz tubes. The tubes
were heated in an electric furnace to 1570 K and kept
for 30 min. Then the furnace was turned off for coolꢀ
ing. Samples were annealed in sealed evacuated quartz
tubes at 970 K for 3000 h.
To check the sample homogeneity, we determined
the element distribution at five different surface areas
of EuLnCuS3 samples (Ln = Nd and Sm) using a Philꢀ
ips SEM 515 microscope (provided by the Tomsk Colꢀ
lective Use Center of Materials Science (TCUCMS)).
The composition of all the areas under analysis correꢀ
sponded to the formula EuLnCuS3. The element disꢀ
tribution map over the sample for the analyzed areas
shows no accumulation of any element (i.e., each eleꢀ
ment is uniformly distributed throughout the sample
surface). Using a Quanta 200 3D system (provided by
TCUCMS) with electron and focused ion beams, we
made a cross section and analyzed the chemical comꢀ
position. The composition of the undersurface layers
unsuitable for the synthesis of the phase EuNdCuS3
;
in addition, samples with Ln = Sm, Ho, and Er conꢀ
tained (Eu, Ln)2O2S as impurities (> 3%). The crystalꢀ
lochemical characteristics of the compound sulfides
EuLnCuS3 (Ln = Gd–Lu) were determined from the
Xꢀray powder diffraction data. It was demonstrated
that the transformation of EuLnCuS3 from the strucꢀ
tural type Eu2CuS3 (space group Pnma; Ln = Gd–Dy)
into the structural type KZrCuS3 (space group Cmcm
;
Ln = Tm–Lu) depends on the size of the rareꢀearth
metal ion. The magnetic properties of the above sulꢀ
fides were studied. For the compounds EuLnCuS3
(Ln = Y, Eu, and Lu) containing nonmagnetic Ln
ions, ferromagnetic ordering of the Eu2+ moments
occurs at 3.4–4.4 K. The compounds EuLnCuS3 conꢀ
taining magnetic Ln ions undergo a ferrimagnetic
transition at ca. 5.0 K [1].
No crystallographic data for EuLnCuS3 (Ln = Nd
and Sm) are available from the literature. The presꢀ
ence of dꢀ and f elements in a crystal lattice can impart
a number of practically useful properties to these comꢀ
pound sulfides. The goal of this study was to obtain the
compounds EuLnCuS3 (Ln = Nd and Sm) and deterꢀ
1
The results of this study have been presented at the X Internaꢀ
tional Scientific Conference “SolidꢀState Chemistry: Nanomaꢀ
terials, Nanotechnologies” (Stavropol, October 17–22, 2010)
[11] and the AllꢀRussia Scientific Conference “Challenges of
Modern Chemistry. Theory and Practice” (Ufa, October 21–23,
2010) [12].
have the formula EuLnCuS3
.
79

80
RUSEIKINA et al.
Table 1. Crystallographic parameters of EuNdCuS3 and EuSnCuS3
Formula
EuNdCuS3
EuSmCuS3
Space group
Pnma
11.0438(2)
4.0660(1)
11.4149(4)
512.58(2)
4
Pnma
10.4202(2)
3.9701(1)
12.8022(2)
529.62(2)
4
a
, Å
, Å
b
c
, Å
V
, Å3
Z
ρcalc, g/cm3
5.908
5.795
Structural type
BaLaCuS3
298
Eu2CuS3
298
T
, K
, Å
λ
1.789010
10–125
1.789010
10–125
2θ, deg
h, k, l
0
≤
h
≤
10, 0
≤
k
≤
4, 0
≤
l
≤
11
0
≤
h
≤
10, 0
≤
k
≤
3, 0
≤
l ≤ 12
R
ꢀDDM, %
8.49
4.6
8.73
4.7
R
Bragg, %
The individuality of the compounds obtained was allowance for the effects of predominant orientation,
confirmed by electronꢀprobe microanalysis and Xꢀray anisotropic peak broadening, and sample surface
powder diffraction. Electronꢀprobe microanalysis was roughness. Data for the isostructural compounds
carried out on a METAM PB microscope. Xꢀray powꢀ BaLaCuS3 [5, 6] and Eu2CuS3 [7, 8] were employed as
der diffraction was examined on a PANalytical X’Pert initial models. Crystallographic parameters and the
PRO diffractometer fitted with a PIXcel detector data collection and refinement statistics are given in
(
CoК radiation). According to Xꢀray powder diffracꢀ Table 1. Experimental, calculated, and difference
α
tion data, the content of the foreign phases in the samꢀ Xꢀray diffraction patterns are shown in Fig. 1. Atomic
ples do not exceed 4 wt %. The lattice parameters of coordinates and isotropic thermal parameters are
EuLnCuS3 (Ln = Nd and Sm) were determined with listed in Tables 2 and 3. The crystallographic data were
the ITO program [3]. The powder diffraction data used to calculate the main shortest anion–cation disꢀ
were used to refine the crystal structures by the derivaꢀ tances (Tables 4, 5). The crystal structures were visualꢀ
tive difference minimization (DDM) method [4] with ized with the Diamond 3 software [9].
I
I
(а)
(b)
10 20 30 40 50 60 70 80 90 100 110 120
2θ, deg
10 20 30 40 50 60 70 80 90 100 110 120
, deg
2
θ
Fig. 1. Experimental (solid line), calculated (dashed line), and difference Xꢀray diffraction patterns (dotted lines) of (a)
EuNdCuS and (b) EuSmCuS for the DDMꢀrefined structures. The positions of the peaks of the main phase are indicated with
3
3
primes.
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 57 No. 1 2012

CRYSTAL STRUCTURES OF EuLnCuS3
81
Table 2. Atomic coordinates and thermal parameters in the
structure of EuNdCuS3
Ln atoms coordinated by the S atoms are between the
chains of the СuS4 tetrahedra. The Eu and Ln ions
occupy two crystallographically independent posiꢀ
tions.
Atom
x
y
z
U
, Å2
Eu
Nd
0.6834(2)
0.0107(2)
0.2557(4)
0.1151(8)
0.4512(7)
0.2765(7)
1/4
1/4
1/4
1/4
1/4
1/4
0.0043(2) 0.013(1)
0.8172(2) 0.013(1)
0.2129(4) 0.020(2)
0.0579(8) 0.013(3)
0.1396(8) 0.015(3)
0.8084(8) 0.015(3)
In both structures, the Eu ions coordinate seven
sulfur ions between the layers of CuLnS3 to form the
monocapped trigonal prism EuS7 (CN = 6 + 1). The
Cu
prisms share two faces along the axis
b and edges along
S(1)
S(2)
S(3)
the axis to form 2D networks in the plane ba. The
а
prism EuS7 consists of the atoms 2S(1) + 2S(2) + S(2) +
2S(3) in EuSmCuS3 and the atoms S(1) + 2S(1) +
2S(2) + 2S(3) in EuSmCuS3. The average Eu–S bond
lengths are 3.024 and 3.059 Å, respectively; the theoꢀ
retical bond length is 3.04 Å [10]. With a decrease in
the Ln3+ ion radius, the Eu–S bonds on average
become lengthened (Tables 4, 5; Fig. 3). This suggests
that the local environment of the Eu atom tends to
transform its geometry and change the structural type,
which is confirmed by the previous data for EuLnCuS3
(Ln = Gd–Lu) [1].
In EuNdCuS3, the coordination polyhedron of the
Nd atom is a monocapped trigonal prism (CN = 6 + 1)
(Fig. 3) made up of the atoms S(1) + 2S(1) + 2S(2) +
S(3) + S(3), the average Nd–S bond length being
2.910 Å. The theoretical bond lengths are 2.823 (for
CN = 6) and 2.949 Å (for CN = 8) [10]. The prisms
NdS7 form a 3D structure with channels housing Eu
and Cu ions. The prisms are joined in pairs along the
Table 3. Atomic coordinates and thermal parameters in the
structure of EuSmCuS3
Atom
x
y
z
U
, Å2
Eu
Sm
0.7840(2)
0.0166(2)
0.2334(3)
0.0482(6)
0.4040(7)
0.2591(6)
1/4
1/4
1/4
1/4
1/4
1/4
0.0019(2) 0.0143(8)
0.7355(1) 0.0108(6)
0.2225(3) 0.017(1)
0.1176(5) 0.011(2)
0.1021(4) 0.015(2)
0.8263(5) 0.011(2)
Cu
S(1)
S(2)
S(3)
axis с, sharing the edges 2S(1)S(1) to form continuous
chains along the direction [010]. The prisms share the
RESULTS AND DISCUSSION
edges 2S(1)S(2) with similar prisms NdS7 and are
linked by the vertices 2S(3) along the axis а.
The crystal structures of the compounds obtained
are shown in Fig. 2. They have layered block strucꢀ
tures. Each copper ion is coordinated to four S atoms
making up a distorted tetrahedron. The vertices of the
CuS4 tetrahedra are occupied by the S(1), S(2), and
two S(3) atoms, the average Cu–S bond lengths being
2.335 (EuNdCuS3) and 2.371 Å (EuSmCuS3). These
bond lengths are somewhat shorter than a theoretical
value of 2.44 Å because of the presence of covalent
bonding. In both structures, the CuS4 tetrahedra are
joined in pairs to produce continuous chains along the
In EuSmCuS3, the Sm atoms located between the
chains of СuS4 tetrahedra have an octahedral environꢀ
ment: 2S(1) + 2S(2) + S(3) + S(3) (Fig. 3). The averꢀ
age Sm–S bond length is 2.798 Å, which is somewhat
shorter than the theoretical value (2.798 Å [10]). The
distorted octahedra SmS6 share the edges 2S(2)S(1)
along the axis b and the vertices 2S(3) along the axis а
to form 2D networks in the ba plane. The octahedra
SmS6 and the tetrahedra CuS4 produce a layer of
CuSmS3 perpendicular to axis
с (as viewed along the
direction [010] (axis
b), sharing the S(3) vertices. The axis
b). In the layer of СuSmS3, the octahedra SmS6
Table 4. Bond lengths
d
in the structure of EuNdCuS3
Bond
d
, Å
Bond
d
, Å
Bond
d, Å
Eu–S(1)
Eu–S(2)
Eu–S(2)
Eu–S(3)
2 × 3.096(7)
2 × 3.007(7)
1 × 2.994(8)
2 × 2.983(7)
3.024
Nd–S(1)
Nd–S(1)
Nd–S(2)
Nd–S(3)
Nd–S(3)
1 × 2.979(9)
2 × 2.845(7)
2 × 2.902(9)
1 × 2.938(8)
1 × 2.957(8)
2.910
Cu–S(1)
Cu–S(2)
Cu–S(3)
1 × 2.354(9)
1 × 2.316(9)
2 × 2.334(5)
2.335
〈Cu–S
〉
〈
Eu–S
〉
〈Nd–S
〉
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 57 No. 1 2012

82
RUSEIKINA et al.
d in the structure of EuSmCuS3
Table 5. Bond lengths
Bond
d
, Å
Bond
d
, Å
Bond
d, Å
Eu–S(1)
Eu–S(1)
Eu–S(2)
Eu–S(3)
1 × 3.127(7)
2 × 3.056(5)
2 × 3.090(6)
2 × 2.996(5)
3.059
Sm–S(1)
Sm–S(2)
Sm–S(3)
Sm–S(3)
2 × 2.817(5)
2 × 2.746(4)
1 × 2.782(7)
1 × 2.797(7)
2.784
Cu–S(1)
Cu–S(2)
Cu–S(3)
1 × 2.351(7)
1 × 2.354(8)
2 × 2.390(4)
2.371
〈Cu–S
〉
〈
Eu–S
〉
〈
Sm–S
〉
share the vertices with each other and share the edges parameter
with the tetrahedra CuS4
c (Table 1). Similar trends have been
.
observed for the unit cell parameters of other isomorꢀ
phic compounds: EuLnCuS3 (Ln = Eu, Gd–Lu) [1, 7,
8] and BaLnMQ3 (M = Cu, Ag, and Au; Q = S, Se,
and Te) [5, 6].
With a decrease in the Ln3+ ion radius, the Ln–S
bonds (Nd–S, 2.910 Å; Sm–S, 2.784 Å) become
shorter, while the average Cu–S bond length slightly
increases. This is accompanied by a decrease in the
To sum up, the structure of EuSmCuS3 consists of
unit cell parameters
a
and b and an increase in the 2D layers (CuSmS3) in the ba plane, which are made
(а)
(b)
a
Eu
Eu
a
c
c
SmS6
CuS4
NdS7
CuS4
a
a
EuS7
EuS7
c
c
Sm
Cu
Nd
Cu
Fig. 2. Projections of the structures of (a) EuNdCuS and (b) EuSmCuS along the [010] direction.
3
3
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 57 No. 1 2012

CRYSTAL STRUCTURES OF EuLnCuS3
83
(а)
(b)
S3
S1
S1
S2
Eu
Eu
S2
>2.98
S1
>3.12
Å
Å
S3
>3.71
S2
S3
Å
S2
>4.16
S3
Å
S3
S2
S1
S2
S1
Sm
Nd
S2
>4.47
S3
S1
S3
Å
Fig. 3. Coordination of Eu and Ln in (a) EuNdCuS and (b) EuSmCuS .
3
3
3. J. W. Visser, J. Appl. Crystallogr.
2, 89 (1969).
up of distorted CuS4 tetrahedra and SmS6 octahedra
with Eu ions between them. The structure of
EuNdCuS3 is a 3D framework (CuNdS3) constructed
from distorted CuS4 tetrahedra and monocapped trigꢀ
onal prisms NdS7 with Eu ions between them. The
crystals of the compounds studied have the identical
symmetry and the same set of atomic positions but
they differ in the bonding system and the coordination
of Nd and Sm.
4. L. A. Solovyov, J. Appl. Crystallogr. 37, 743 (2004).
5. A. E. Christuk, P. Wu, and J. A. Ibers, J. Solid State
Chem. 110, 330 (1994).
6. P. Wu, A. E. Christuk, and J. A. Ibers, J. Solid State
Chem. 110, 337 (1994).
7. P. Lemoine, D. Carré, and M. Guittard, Acta Crystalꢀ
logr. 42, 390.
8. F. Furuuchi, M. Wakeshima, and Y. Hinatsu, J. Solid
State Chem. 177, 3853 (2004).
ACKNOWLEDGMENTS
9. K. Brandenburg, DIAMOND—Visual Crystal Structure
Information System (CRYSTAL IMPACT, Postfach
1251, Dꢀ53002 Boon, Germany).
This work was supported by the Federal Target Proꢀ
gram “Scientific and Pedagogical Personnel of Innoꢀ
vative Russia” for 2009–2013 (grant nos. 6K/143ꢀ09
(P 646) and NKꢀ409/5 (P2263)) and the President of
the Russian Federation (Support Program for Leading
Scientific Schools of the Russian Federation, grant
NShꢀ4645.2010.2).
10. R. D. Shannon, Acta Crystallogr., Sect. A: 32, 751
(1976).
11. A. V. Ruseikina, O. V. Andreev, and L. A. Solov’ev, Proꢀ
ceedings of the 10th International Conference “Solid
State Chemistry: Nanomaterials, Nanotechnologies
,
Stavropol, 2010” (SevKavGTU, Stavropol, 2010), p. 89
[in Russian].
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RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 57 No. 1 2012