Crystal structure of EuCeCuS3

Article abstract of DOI:10.1134/S0036023616110176

The crystal structure of EuCeCuS₃, a complex sulfide synthesized for the first time, has been solved using X-ray powder diffraction data. Crystals are rhombic, space group Pnma, Ba₂MnS₃ structural type, a = 8.1023(1) ?, b = 4.0386(1) ?, c = 15.9022(2) ?, V = 520.36(1) ?³, Z = 4, ρ_calcd = 5.767 g/cm³. The Eu,CeS₇ polyhedron incorporates the Eu and Ce atoms, which are randomly disordered over two crystallographic sites. The bond lengths d_Eu,Ce–S range from 2.885 to 3.044 ?.

Full text of DOI:10.1134/S0036023616110176

ISSN 0036-0236, Russian Journal of Inorganic Chemistry, 2016, Vol. 61, No. 11, pp. 1403–1407. © Pleiades Publishing, Ltd., 2016.
Original Russian Text © A.V. Ruseikina, 2016, published in Zhurnal Neorganicheskoi Khimii, 2016, Vol. 61, No. 11, pp. 1456–1460.
COORDINATION
COMPOUNDS
Crystal Structure of EuCeCuS3
A. V. Ruseikina
Tyumen State University, ul. Semakova 10, Tyumen, 625003 Russia
e-mail: adeschina@mail.ru
Received November 10, 2015
Abstract—The crystal structure of EuCeCuS , a complex sulfide synthesized for the first time, has been
3
solved using X-ray powder diffraction data. Crystals are rhombic, space group Pnma, Ba MnS structural
2
3
3
3
type, a = 8.1023(1) Å, b = 4.0386(1) Å, c = 15.9022(2) Å, V = 520.36(1) Å , Z = 4, ρ
= 5.767 g/cm . The
calcd
Eu,CeS polyhedron incorporates the Eu and Ce atoms, which are randomly disordered over two crystallo-
7
graphic sites. The bond lengths d
range from 2.885 to 3.044 Å.
Eu,Ce–S
DOI: 10.1134/S0036023616110176
The crystal structures of АCeCuS (А = Sr, Ba) alloying a mixture of initial sulfides EuS, Ce S , and
3
2 3
were solved using X-ray powder diffraction data [1–3]. Cu S at a ratio 2 : 1 : 1 in a graphite crucible placed into
2
ВаCeCuS is isostructural to Eu CuS [1, 2]. SrCe- an evacuated and sealed quartz ampoule. The ampoule
3
2
3
CuS has two polymorphs of rhombic symmetry was heated in an electrical furnace to 1570 K and
3
(
space group Pnma): α-SrCeCuS of BaLaCuS
allowed to stand for 30 min. Cooling was performed in
the switch-off furnace. Samples were annealed at 970 K
for 4 months and at 1170 K for 2 months [6, 7].
3
3
structural type (at 970 K) with unit cell parameters a =
1.1626(2) Å, b = 4.0970(2) Å, and c = 11.5307(1) Å
and β-SrCeCuS of Ba MnS structural type (at 1170
1
X-ray powder diffraction analysis of EuCeCuS was
3
2
3
3
K) with a = 8.1393(3) Å, b = 4.0587(2) Å, and c = performed on a PANalytical X’Pert PRO diffractome-
1
5.9661(2) Å. The Sr and Ce atoms in α- and β-SrСe- ter (CoK radiation, graphite monochromator, PIXcel
α
CuS are observed to be disordered over two crystallo- detector) within the angle range of 10° ≤ 2θ ≤ 140°.
3
graphic sites. The site occupancy is 0.84:0.16 (α-) and Samples were prepared by pounding with addition of
0
.58:0.42 (β-), respectively [3]. The ratio between the octane in an agate mortar. The unit cell parameters
were determined with the ITO software [8].
radii of seven-coordinated ions rBa2+ : rSr2+ : rEu2+ = 1.38 :
According to the data of X-ray powder diffraction
and microstructural analysis (METAM LV-31 micro-
scope), the 2EuS: 1Ce S : 1Cu S sample annealed at
1
.21 : 1.2 [4] allows us to predict the formation of
EuCeCuS . Close values of r
Sr2+
and rEu2+ enable
3
2
3
2
EuCeCuS to crystallize in one of the Ba MnS /
3
2
3
1
170 K contained EuCeCuS alone. Element distribu-
3
BaLaCuS structural types, and there is also some
3
tion spectra were determined on a Philips SEM JEOL
JSM-6510 LM scanning electron microscope at five
different points on the surface of a sample. The com-
positions of all the analyzed areas corresponded to
probability for the existence of polymorphs. No crys-
tallographic data were found for EuCeCuS in the lit-
3
erature.
Here, we report some results of solving the crystal
EuCeCuS . X-ray spectral microanalysis results coin-
3
structure of EuCeCuS with the use of X-ray powder
diffraction data.
3
cided with theoretical values within a measurement
accuracy of 0.2 wt %. The crystal structure of EuCe-
CuS (annealing at 1170 K) was refined by the deriva-
3
tive difference minimization (DDM) method in the
anisotropic approximation for all atoms with the reli-
EXPERIMENTAL
Cu S was synthesized from elementary copper (11-4
2
ability factors R-DDM = 4.88% and R = 1.61%. The
F
high purity grade) and sulfur (15-3 high purity grade)
in ampoules. Се S and EuS were synthesized from
data for isostructural PbLaCuS were used as an initial
3
2
3
structural model [9]. Refinement was performed tak-
ing into account the effects of preferred orientation,
anisotropic broadening of peaks, and sample surface
oxides of TseO-L and EvO-Zh grade in an Н S and
2
СS flow at 1300 K [5]. According to X-ray powder
2
diffraction data, the synthesized sulfides were single roughness and displacement. Anion–cation distances
phases and had a stoichiometric composition within and selected bond angles are given in Tables 1 and 2,
chemical analysis error. EuCeCuS was prepared by respectively. The experimental, calculated, and differ-
3
1403

1404
RUSEIKINA
Table 1. Interatomic distances (d) in the structure of β-EuСeCuS3
Bond
d, Å
Bond
d, Å
3.014(4)
2 × 2.925(3)
2 × 2.984(3
2 × 3.058(4)
2.992(2)
Bond
Cu–S1
Cu–S2
Cu–S3
〈Cu–S〉
d, Å
(
(
(
(
(
Ce1,Eu2)–S1
Ce1,Eu2)–S1
Ce1,Eu2)–S2
Ce1,Eu2)–S3
Ce1,Eu2)–S3
2 × 2.923(3)
3.044(4)
2.969(5)
2 × 2.885(3)
3.052(5)
(Eu1,Ce2)–S1
(Eu1,Ce2)–S2
(Eu1,Ce2)–S2
(Eu1,Ce2)–S3
〈(Eu1,Ce2–S)〉
2 × 2.354(2)
2.365(5)
2.356(5)
2.357(2)
〈
(Ce1,Eu2)–S〉
2.954(2)
ence X-ray powder diffraction patterns after DDM occupancies). Longer annealing is required for the
refinement are shown in comparison in Fig. 1. The synthesis of a homogeneous α-EuCeCuS sample.
3
crystal structures were visualized using the Diamond 3
software suite [10].
RESULTS AND DISCUSSION
The 2EuS : 1Ce S : Cu S sample annealed at 970 K
2
3
2
The X-ray powder diffraction pattern of β-EuCe-
contained two EuCeCuS polymorphs, namely, 73.8%
3
CuS (annealing at 1170 K) was indexed in in terms of
3
of Ba MnS structural type (a = 8.0991(1) Å, b =
2
3
orthorhombic crystal system, Ba MnS structural
2
3
4
.03978(4) Å, c = 15.8979(1) Å) and 20.1% of
type, with unit cell parameters a = 8.1023(1) Å, b =
BaLaCuS structural type (a = 11.1174(2) Å, b =
3
3
4.0386(1) Å, c = 15.9022(2) Å; V = 520.36(1) Å , Z = 4,
3
4
.07142(9) Å, c = 11.4837(2) Å), which were denoted
and ρ
= 5.767 g/cm . β-EuCeCuS has a layered-
calcd
3
as β- and α-modifications, respectively, alongside
block structure (Fig. 2). Continuous chains of dis-
with some admixtures, such as 0.6% of EuS, 0.9% of
torted СuS tetrahedra sharing apical S1 atoms along
4
CuCeS , and 4.6% of Eu CuS . Since the sample rep-
2
2
3
direction [010] are spaced by seven-coordinated Sr
resented a mixed phase and was poorly crystallized, no and Ce atoms, which form one-capped trigonal
refinement was performed for the structure of EuCе- (Eu,Ce)S prisms. The crystallographic sites of euro-
7
CuS (coordinates, thermal parameters, atomic site pium and cerium are mixed by 35%. Similar disorder-
3
I1/2
1
2
3
20
30
40
50
60
70
80
90 100 110 120 130 140
2θ, deg
Fig. 1. (1) Experimental, (2) calculated, and (3) difference X-ray powder diffraction patterns of the 2EuS : 1Сe S : 1Cu S sample
2
3
2
after DDM refinement of its structure. Main phase peak positions are shown with strokes.
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY
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CRYSTAL STRUCTURE OF EuCeCuS3
Table 2. Selected bond angles in the structure of β-EuCeCuS3
1405
Angle
ω, deg
Angle
ω, deg
Angle
ω, deg
S1(Ce1,Eu2)S1
S1(Ce1,Eu2)S1
S1(Ce1,Eu2)S2
S1(Ce1,Eu2)S3
S1(Ce1,Eu2)S3
S2(Ce1,Eu2)S1
S2(Ce1,Eu2)S3
S3(Ce1,Eu2)S1
S3(Ce1,Eu2)S1
S3(Ce1,Eu2)S1
S3(Ce1,Eu2)S2
S3(Ce1,Eu2)S3
S3(Ce1,Eu2)S3
87.40(9)
78.00(8)
78.47(9)
S1(Eu1,Ce2)S3
S2(Eu1,Ce2)S1
S2(Eu1,Ce2)S1
S2(Eu1,Ce2)S2
S2(Eu1,Ce2)S2
S2(Eu1,Ce2)S2
S2(Eu1,Ce2)S2
S2(Eu1,Ce2)S3
S2(Eu1,Ce2)S3
S2(Eu1,Ce2)S3
S2(Eu1,Ce2)S3
S3(Eu1,Ce2)S3
138.35(10)
79.63(9)
77.71(9)
S1CuS1
118.12(13)
S1CuS3
S1CuS2
S3CuS2
108.64(13)
108.96(13)
102.36(14)
125.12(10)
143.98(10)
147.24(10)
68.78(10)
80.34(9)
158.33(10)
87.84(10)
121.12(10)
74.19(10)
88.83(10)
157.30(10)
87.34(10)
89.3(10)
85.18(10)
131.86(10)
75.84(98)
121.82(10)
68.50(10)
82.65(10)
ing also appears in isostructural ALnCuS crystals
dLn–S: 2.975 (dLa1–S [11]) → 2.954 (dCe1–S, Table 1)
→ 2.719 (dPr1–S [12]) Å;
3
(
А = Eu, Sr, Pb; Ln = La, Ce, Pr) [3, 5, 9, 11, 12].
A one-capped trigonal Се1S prism is built of 2S1 +
7
3.003 (dLa2–S [11]) → 2.992 (dCe2–S, Table 1)
S1 + S2 + 2S3 + S3 atoms with an average Се1–S dis-
→
2.983 (dPr1–S [12]) Å;
tance of 2.954 Å (Table 1) at a theoretical value of
.955 Å calculated from the ionic radii rCe3+ = 1.07 and
rEu2+ = 1.20 Å (CN = 7) [4] with consideration for the
dCu–S: 2.359 [11] → 2.357 (Table 1)
2.348 [12] Å.
2
→
Hence, the established X-ray and structural
site occupancy Ce1 : Eu2 = 0.652 : 0.348. One-capped
parameters of β-EuCeCuS agree with a natural
3
trigonal Ce1S prisms share 2 × S1S1 and 2 × S3S3
7
change in the parameters, bond lengths, and structural
edges along axis a and 2 × S3S1 edges along axis b to
form two-dimensional networks in plane аb. A one-
types obtained for the series of EuLnCuS (Ln = La,
3
Pr, Nd, Sm–Dy, Tm–Lu) correlated with a change in
capped trigonal Eu1S prism is built of S1 + 2S2 + 2S2 +
7
3+
the Ln ionic radius in the earlier works [5–7, 11–13].
2
(
S3 atoms with an average Eu1–S distance of 2.992 Å
theoretical value, 2.994 Å). Eu1S prisms share 2 ×
The crystal structures of AСeCuS (А = Sr, Eu) are
3
7
S2S2 edges along axis а and 2 × S2S2S3 faces along observed to have some similarity due to close rSr2+ and
axis b to form two-dimensional networks in plane аb.
rEu2+. The various bond lengths d(А,Сe)–S in ACeCuS3
One-capped trigonal Eu1S and Се1S prims share
7
7
(
A = Sr, Eu) produce a difference between their unit
cell parameters and volumes and X-ray densities.
edges to form a three-dimensional network with chan-
2+
nels accommodating Cu ions.
The structural characteristics of β-EuCeCuS are
Small values of the average bond lengths d
=
=
Eu1–S
3
2.992(2) Å and d
= 2.954(2) Å (EuCeCuS ) in
Сe1–S
3
intermediate between EuLaCuS [11] and β-EuPr-
3
comparison with d
= 3.004(2) Å and d
Sr1–S Сe1–S
CuS [12]. The unit cell parameters of EuLnCuS (Ln =
3
3
2.971(2) Å (SrCeCuS [3]) are due to the facts that
3
La [11], Ce, Pr [12]) annealed at 1170 K naturally
decrease:
(
1) The covalent component of the (Eu,Ce)–S
bond is less pronounced than for the (Sr,Ce)–S bond.
a = 8.1366 (EuLaCuS [11]) → 8.1023 (β-EuCeCuS ) This agrees with the theoretical notions about that
3
3
rare-earth elements (as transition metals) have an
insufficient bond ionicity in comparison with alkali-
earth elements [14]; and
→
8.0786 (β-EuPrCuS [12]) Å;
3
b = 4.0586 (EuLaCuS [11]) → 4.0386 (β-EuCeCuS )
3
3
→
4.0288 (β-EuPrCuS [12]) Å;
3
(
2) rEu2+ < rSr2+. This in turn is caused by the elec-
2
7
0
2
c = 15.9822 (EuLaCuS [11]) → 15.9022 (β-EuCeCuS )
3
3
tron structure of Sr (5s ) and Eu (4f 5d 6s ) and the
→
15.8389 (β-EuPrCuS [12]) Å.
lanthanide contraction effect.
3
It is likely that small differences between r and
A2+
The average values of d
and d
are also
Ln–S
Cu–S
observed to sustain a natural decrease with descending rCe3+ (ΔrSr–Ce = 11.5%, Δr
= 10.8%) cause the dis-
Eu–Ce
3+
2+
rLn3+ in the series of EuLnCuS3:
placement of А and Сe crystallographic sites.
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 61 No. 11 2016

1406
RUSEIKINA
(а)
a
b
c
Eu, Ce
CuS4
(b)
S3
S3
S1
a
S3
S3
Ce1
c
S3
S1
S1
Cu
S2
S2
Eu1
S2
S2
S2
Eu1
Cu
S1
S1
S1
S1
S3
Ce1
Ce1
S3
S1
S1
S1
S1
Cu
S2
S2
Eu1
S2
S2
S2
Eu1
S2
Cu
S1
S1
S3
S3
S3
Ce1
S3
S3
S1
Fig. 2. Projections [010] for the structure of β-EuCeCuS3.
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY
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CRYSTAL STRUCTURE OF EuCeCuS3
1407
Hence, two polymorphs have been revealed for
2. L. A. Koscielski, Z. Anorg. Allg. Chem. 638, 2585
(
2012).
3. A. V. Ruseikina, L. A. Solov’ev, Russ. J. Inorg. Chem.
1, 482 (2016).
4. R. D. Shannon, Acta Crystallogr., Sect. A 32, 751
1976).
EuCeCuS : low-temperature α-EuCeCuS (BaLaCuS
3
3
3
structural type) and high-temperature β-EuCeCuS
3
6
(
Ba MnS structural type), which are similar to the mod-
2 3
ifications appearing for EuPrCuS [12] and SrCeCuS
3
3
(
[
3]. The crystal structure of β-EuCeCuS (annealing
3
at 1170 K) has been solved. The cerium and europium
atoms in this structure are randomly disordered over
two crystallographic sites. It should be expected that
the disordering of rare-earth element atoms over sites
will be retained at a lower annealing temperature (970 K)
5. A. V. Ruseikina, L. A. Solov’ev, and O. V. Andreev,
Russ. J. Inorg. Chem. 59, 196 (2014).
6. A. V. Ruseikina, L. A. Solovyev, O. V. Andreev, and
A. A. Kislitsyn, Russ. J. Inorg. Chem. 59, 1109 (2014).
7
. A. V. Ruseikina, L. A. Solovyev, M. S. Molokeev, and
as for SrCeCuS [3]. Longer annealing is required for the
O. V. Andreev, Russ. J. Inorg. Chem. 57, 79 (2012).
3
synthesis of a homogeneous α-EuCeCuS sample
3
8. J. W. Visser, J. Appl. Crystallogr. 2, 89 (1969).
. T. D. Brennan and J. A. Ibers, J. Solid State Chem. 97,
77 (1992).
(
annealing at 970 K).
9
3
ACKNOWLEDGMENTS
10. K. Brandenburg, DIAMOND: Visual Crystal Structure
Information System CRUSTAL IMPACT (Postfach
The author of this paper is grateful to L.A. Solov’ev, a
researcher of the Institute of Chemistry and Chemical
Technology of the Siberian Branch of the Russian
Academy of Sciences (Krasnoyarsk), for performing
the X-ray powder diffraction analysis of sulfide.
This work was financially supported by state task
no. 2014/228, research project no. 996.
1251, D-53002 Boon).
1
1. A. V. Ruseikina, L. A. Solov’ev, and O. V. Andreev,
Russ. J. Inorg. Chem. 57, 574 (2012).
1
2. A. V. Ruseikina, L. A. Solov’ev, and O. V. Andreev,
Russ. J. Inorg. Chem. 58, 1231 (2013).
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1
4. D. V. Shriver and P. W. Atkins, Inorganic Chemistry, 3rd ed.
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. P. Wu, A. E. Christuk, and J. A. Ibers, J. Solid State
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Translated by E. Glushachenkova
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 61 No. 11 2016