Simultaneous presence of (Si3O10)8- and (Si2O7)6- groups in new synthetic mixed sorosilicates: BaY4(Si2O7)(Si3O 10) and isotypic compounds, studied by single-crystal X-ray diffraction, Raman spectroscopy and DFT calculations

Article abstract of DOI:10.1016/j.jssc.2013.09.007

Three new, isotypic silicate compounds, BaY₄(Si ₂O₇)(Si₃O₁₀), SrYb ₄(Si₂O₇)(Si₃O₁₀) and SrSc₄(Si₂O₇)(Si₃O₁₀), were synthesized using high-temperature flux growth techniques, and their crystal structures were solved from single-crystal X-ray intensity data: monoclinic, P2₁/m, with a=5.532(1)/5.469(1)/5.278(1), b=19.734(4)/19.447(4)/19.221(4), c=6.868(1)/6.785(1)/6.562(1) A, β=106.53(3)/106.20(3)/106.50(3), V=718.8(2)/693.0(2)/638.3(2) A³, R(F)=0.0225/0.0204/0.0270, respectively. The topology of the novel structure type contains isolated horseshoe-shaped Si₃O ₁₀ groups (Si-Si-Si=93.15-95.98), Si₂O₇ groups (Si-O_bridge-Si=180, symmetry-restricted) and edge-sharing M(1)O ₆ and M(2)O₆ octahedra. Single-crystal Raman spectra of the title compounds were measured and compared with Raman spectroscopic data of chemically and topologically related disilicates and trisilicates, including BaY₂(Si₃O₁₀) and SrY₂(Si ₃O₁₀). The band assignments are supported by additional theoretical calculation of Raman vibrations by DFT methods.

Full text of DOI:10.1016/j.jssc.2013.09.007

Journal of Solid State Chemistry 207 (2013) 94–104
Contents lists available at ScienceDirect
Journal of Solid State Chemistry
journal homepage: www.elsevier.com/locate/jssc
Simultaneous presence of (Si3O10)8ꢀ and (Si2O7)6ꢀ groups in new
synthetic mixed sorosilicates: BaY4(Si2O7)(Si3O10) and isotypic
compounds, studied by single-crystal X-ray diffraction, Raman
spectroscopy and DFT calculations
b
c,d
Maria Wierzbicka-Wieczorek a, , Daniel M. Többens , Uwe Kolitsch
,
n
Ekkehart Tillmanns d
a Institut für Geowissenschaften, Friedrich-Schiller-Universität Jena, Carl-Zeiss-Promenade 10, D-07745 Jena, Deutschland
b Abteilung Kristallographie, Helmholtz-Zentrum Berlin, Hahn-Meitner-Platz 1, D-14109 Berlin, Deutschland
c Mineralogisch-Petrographische Abt., Naturhistorisches Museum, Burgring 7, A-1010 Wien, Austria
d Institut für Mineralogie und Kristallographie, Universität Wien, Geozentrum, Althanstraße 14, A-1090 Wien, Austria
a r t i c l e i n f o
a b s t r a c t
Article history:
Three new, isotypic silicate compounds, BaY4(Si2O7)(Si3O10), SrYb4(Si2O7)(Si3O10) and SrSc4(Si2O7)(Si3O10), were
synthesized using high-temperature flux growth techniques, and their crystal structures were solved from
single-crystal X-ray intensity data: monoclinic, P21/m, with a¼5.532(1)/5.469(1)/5.278(1), b¼19.734(4)/19.447
(4)/19.221(4), c¼6.868(1)/6.785(1)/6.562(1) Å, β¼106.53(3)/106.20(3)/106.50(3)1, V¼718.8(2)/693.0(2)/638.3
(2) Å3, R(F)¼0.0225/0.0204/0.0270, respectively. The topology of the novel structure type contains isolated
horseshoe-shaped Si3O10 groups (Si–Si–Si¼93.15–95.981), Si2O7 groups (Si–Obridge–Si¼1801, symmetry-
restricted) and edge-sharing M(1)O6 and M(2)O6 octahedra. Single-crystal Raman spectra of the title
compounds were measured and compared with Raman spectroscopic data of chemically and topologically
related disilicates and trisilicates, including BaY2(Si3O10) and SrY2(Si3O10). The band assignments are supported
by additional theoretical calculation of Raman vibrations by DFT methods.
Received 21 June 2013
Received in revised form
3 September 2013
Accepted 4 September 2013
Available online 14 September 2013
Keywords:
Flux-growth method
Crystal structure
Sorosilicates
Single-crystal X-ray diffraction
Raman spectroscopy
DFT calculations
& 2013 Elsevier Inc. All rights reserved.
1. Introduction
SrSc4(Si2O7)(Si3O10) are also reported and a comparison is made
with compounds having related topologies and chemical composi-
Natural or synthetic compounds with mixed polyhedral arrange-
ments based on M2O7 and M3O10 (M¼Si, V, As, P in tetrahedral
coordination) groups are very rare. Considering the M2O7:M3O10 ratio
for crystal structures, it is found that only one representative with the
ratio 1:1 exists, viz. the vanadate (V) NaCa3Mn(V2O7)(V3O10) [1].
Presently, only one silicate containing M2O7:M3O10 groups with the
ratio 2:1, namely BaYb6(Si2O7)2(Si3O10), is known [2]. This silicate is
isotypic to six phosphate and arsenate, compounds: NH4Cd6(P2O7)2
(P3O10) [3], KMn6(P2O7)2(P3O10), AgMn6(P2O7)2(P3O10) [4], NaMn6
(P2O7)2(P3O10), KCd6(P2O7)2(P3O10) [5], and RbMn6(As2O7)2(As3O10) [6].
This report presents the high-temperature flux-growth synth-
eses, crystal-structures and Raman spectra of three new isotypic
silicate compounds, BaY4(Si2O7)(Si3O10), SrYb4(Si2O7)(Si3O10), and
SrSc4(Si2O7)(Si3O10). DFT calculations for BaY4(Si2O7)(Si3O10), and
tions. These three silicates appear to represent the first mixed
sorosilicate representatives with arrangements of Si2O7 and Si3O10
groups in the ratio 1:1, and having no additional silicate groups.
The present contribution is part of a larger study of the synthesis,
crystal chemistry, and topologies of mixed octahedral–tetrahedral
framework MI–(MII–)MIII-silicates (MI¼Na, K, Rb, Cs; MII¼Sr, Ba;
MIII¼Sc, V, Cr, Fe, In, Y, Gd, Yb), having potential applications in
the fields of separation, ion exchange, catalysis, luminescence, and
X-ray scintillation [7–15].
2. Experimental
2.1. Synthesis and physicochemical characterization
All three silicates were synthesized at high temperature by flux-
growth [16–18]. Mixtures of oxides of the M3þ-metals, and carbonates
or hydroxide precursor compounds of the earth-alkaline and alkali
metals, and a MoO3 solvent were transferred into platinum crucibles,
n
Corresponding author. Tel.: þ49 3641 948722; fax: þ49 3641 948702.
E-mail address: maria.wierzbicka-wieczorek@uni-jena.de
(M. Wierzbicka-Wieczorek).
0022-4596/$ - see front matter & 2013 Elsevier Inc. All rights reserved.
http://dx.doi.org/10.1016/j.jssc.2013.09.007

M. Wierzbicka-Wieczorek et al. / Journal of Solid State Chemistry 207 (2013) 94–104
95
which were covered with lids to avoid excessive solvent evaporation,
and heated in air to 1150 1C over a period of 12 h in a Naber furnace.
After a holding time of 3 h, the reacted mixtures were slowly cooled at
2 K/h over a 125 h period to 900 1C, after which step the furnace was
switched off. The final products were washed in distilled water,
filtered, and dried in air at room temperature.
Trial experiments showed that the precursor-to-solvent ratio
has an important role in determining the size and amount of the
product crystals; the compounds presented here were prepared
using optimized starting mixtures. BaY4(Si2O7)(Si3O10) crystallized
from a starting mixture of 0.1630 g Y2O3, 0.1735 g SiO2, 0.4293 g
Cs2CO3, 1.0007 g BaCO3, and 1.0035 g MoO3 as small colorless
prisms (Fig. 1a). The crystals were accompanied by Cs3YSi8O19
[8,12], which is isotypic with Cs3ScSi8O19 [19], and scheelite-type
BaMoO4.
A JEOL JSM 6400 scanning electron microscope (SEM) was used
for the analysis of the chemical composition of the grown crystals
and the characterization of their morphology. Crystals were fixed
on adhesive carbon tape, made conductive by carbon-coating, and
analyzed by an energy-dispersive X-ray (EDX) analyzer (KEVEX
system with LINK analytical software). The SEM-EDX analysis of
BaY4(Si2O7)(Si3O10) showed the presence of only Ba, Y, and Si.
The molar ratio of the precursor compounds used for the
optimized crystal growth of BaY4(Si2O7)(Si3O10) was successfully
adopted to prepare two further isotypic compounds. SrYb4(Si2O7)
(Si3O10) (Fig. 1b) crystallized from a mixture containing 0.1658 g
Yb2O3, 0.1685 g SiO2, 0.8013 g Rb2CO3, 1.0005 g Sr(OH)2 ꢁ 8H2O,
and 1.0049 g MoO3. The only accompanying phase was scheelite-
type SrMoO4. No metals other than Sr, Yb and Si were detected by
SEM-EDX. SrSc4(Si2O7)(Si3O10) (Fig. 1c) was synthesized from a
starting mixture of 0.1253 g Sc2O3, 0.2122 g SiO2, 0.8017 g Rb2CO3,
0.9988 g Sr(OH)2 ꢁ 8H2O, and 0.9997 g MoO3. The only phase
accompanying the silicate was scheelite-type SrMoO4. The SEM-
EDX analysis confirmed the presence of Sr, Sc and Si.
Single-crystal unpolarized Raman spectroscopy was used to
study the vibrational modes of Si2O7 and Si3O10 units in the
synthesized sorosilicates, which were then compared to spectra
of chemically and topologically related disilicates and trisilicates
previously synthesized by us, and to data from the literature.
Spectra in the range 200ꢀ1200 cmꢀ1 were recorded at room
temperature from randomly oriented crystals under quasi-
backscattering geometry, using a notch filter-based Renishaw
RM1000 micro-Raman spectrometer equipped with a Leica DMLM
optical microscope (Leica 50 ꢂ objective, numerical aperture 0.75).
All spectra were excited with the 488 nm emission of an Arþ laser
(8 mW measured behind the objective). The wavenumber accu-
racy (calibrated using Ne lamp emissions) was 0.5 cmꢀ1, and the
spectral resolution was 2.5 cmꢀ1. The system was operated in the
quasi-confocal mode, resulting in a lateral resolution of ꢃ5 μm.
2.2. Crystal-structure determination
A
Nonius KappaCCD single-crystal X-ray diffractometer
equipped with a 300 μm diameter capillary-optics collimator was
used to determine the crystal structure of all three compounds.
The intensity data obtained from selected crystals or crystal
fragments were processed with the Nonius program suite
DENZO-SMN and corrected for Lorentz, polarization, and back-
ground effects, and, by the multi-scan method [20], for absorption.
The crystal structure of BaY4(Si2O7)(Si3O10) was solved by direct
methods (SHELXS-97, [21]) in space group P21/m and subsequent
Fourier and difference-Fourier syntheses; final atomic coordinates
and displacement parameters refined by full-matrix least-squares
techniques on F2 using SHELXL-97 [21]. PLATON [22] confirmed
the validity of the structure model. The refinements of the crystal
structures of the two other isotypic compounds, SrYb4(Si2O7)
(Si3O10), and SrSc4(Si2O7)(Si3O10), were started adopting the struc-
ture model of BaY4(Si2O7)(Si3O10). The final residuals for the
BaY-, SrYb-, and SrSc-compounds were R(F)¼0.0225, 0.0204, and
0.0270, respectively. Refinements of occupancies showed that all
sites are fully occupied. More details on crystal data, measure-
ments, and refinements are provided in Table 1. The final values of
Fig. 1. SEM images of flux-grown crystals of (a) BaY4(Si2O7)(Si3O10),
(b) SrYb4(Si2O7)(Si3O10), (c) SrSc4(Si2O7)(Si3O10).

96
M. Wierzbicka-Wieczorek et al. / Journal of Solid State Chemistry 207 (2013) 94–104
Table 1
Crystal data, data collection information and refinement details.
Formula
SrSc4(Si2O7)(Si3O10
)
SrYb4(Si2O7)(Si3O10
)
BaY4(Si2O7)(Si3O10)
Crystal data
Formula weight
Space group, Z
Crystal dimens. (mm3)
a (Å)
679.91
P21/m, 2
1192.23
P21/m, 2
905.43
P21/m, 2
0.02 ꢂ 0.06 ꢂ 0.07
0.02 ꢂ 0.04 ꢂ 0.08
0.03 ꢂ 0.04 ꢂ 0.12
5.278(1)
5.469(1)
5.532(1)
b (Å)
c (Å)
19.221(4)
6.562(1)
106.50(3)
638.3(2)
656, 3.538
6.750
19.447(4)
6.785(1)
106.20(3)
693.0(2)
1048, 5.714
31.084
19.734(4)
6.868(1)
106.53(3)
718.8(2)
836, 4.183
19.186
β (1)
V (Å3)
F (000), ρcalc (g/cm3)
m (mmꢀ1
)
Absorption correction
Multi-scan
Multi-scan
Multi-scan
Data collection
Diffractometer
Nonius KappaCCD system
Nonius KappaCCD system
Nonius KappaCCD system
Crystal-detector dist. (mm)
2θmax (1), T (K)
30
65, 293
34
65, 293
36
65, 293
Rotation axis, width (1)
Total no. of frames
Collect. time per degree (s)
φ, ω, 1
448
φ, ω, 2
492
φ, ω, 1
1001
100
150
140
ꢀ7/7, ꢀ28/29, ꢀ9/9
ꢀ8/8, ꢀ29/29, ꢀ10/10
ꢀ8/8, ꢀ29/29, ꢀ10/10
h, k, l ranges
Total reflections measured
4601
5035
5191
Unique reflections
2365 (Rint 0.0247)
2582 (Rint 0.0175)
2662(Rint 0.0209)
Refinement
Refinement on
F2
F2
F2
No. of refined parameters
131
131
131
R1(F), wR2(F2)
all
0.0270, 0.061
0.0011(5)
2024 [Fo44s(Fo)]
0.0207, 0.053
0.00153(12)
2455 [Fo44s(Fo)]
0.0225, 0.055
0.0011(2)
2419 [Fo44s(Fo)]
Extinction coefficient
‘Observed’ refls.
GooF
1.086
1.134
1.090
(Δ/s)max
0.001
0.004
0.002
Δρmin, Δρmax (e/Å3)
a, ba
ꢀ0.64, 0.89
ꢀ1.85, 0.31
ꢀ1.28, 1.17
0.023, 0.75
0.028, 2.44
0.026, 1.0
a
w¼1/[(s2(Fo2)þ(a ꢁ P)2þb ꢁ P]; P¼[max(0, Fo2)þ2 ꢁ Fo2]/3.
atom positions and anisotropic displacement parameters are given
in Tables 2 and 3. Table 4 gives selected geometric parameters and
calculated bond-valence sums [24,25] for coordination polyhedra.
Further details on the crystal structure investigation may be obtained
from the Fachinformationszentrum Karlsruhe, 76344 Eggenstein-
Leopoldshafen, Germany (Fax: þ49-7247-808-666; e-mail: crys
data@fiz-karlsruhe.de), on quoting the depository number CSD-
426325 (BaY4(Si2O7)(Si3O10)), CSD-426326 (SrSc4(Si2O7)(Si3O10)),
and CSD-426327 (SrYb4(Si2O7)(Si3O10)).
were used [33], for yttrium in form of a HAYWSC-311G(11) con-
traction based on the unpublished expansion of Gennard and Furio
given in the CRYSTAL basis sets library [34], for scandium a
HAYWSC-311G(31) contraction [35], and for strontium and barium
HAYWSC-311G(1) contractions [36]. For all basis sets the exponents
of the two most diffuse sp shells and of the most diffuse d shell
have been optimized to the following values: sp(O)¼0.448, 0.154,
d(O)¼0.615, sp(Si)¼0.476, 0.169, d(Si)¼0.682, sp(Y)¼0.351, 0.13,
d(Y)¼0.341, sp(Sc)¼0.551, 0.324, d(Sc)¼0.386, sp(Sr)¼0.667, 0.262,
d(Sr)¼0.443, sp(Ba)¼0.508, 0.213, d(Ba)¼0.312. The lattice para-
meters of the fully relaxed structures were in very good agreement
with the experimental values, with the calculated values r1.0 % too
large; the monoclinic angles agree within 0.11 (see Table 5).
The DFT calculation for SrYb4(Si2O7)(Si3O10) was unsuccessful
because the optimized structure deviated too much from the
experimental one. No adequate optimized model for the Yb atom
could be found.
The coordinate sets of all structures were standardized with the
program STRUCTURE TIDY [26]. Drawings of the polyhedral
arrangements were prepared with the program ATOMS [27].
2.3. Density functional theory (DFT) calculation of Raman shifts
2.3.1. Computational parameters
Calculations of Raman shifts were performed with the program
CRYSTAL 09 [28] from first principles using 3D-periodic density
functional theory with Gaussian basis sets. The vibrational fre-
quencies were calculated at Γ-point from numerically computed
second derivatives of the energy at a stationary point on the
potential energy surface [29]. A Pack–Monkhorst k net with
4 ꢂ 4 ꢂ 4 points in the Brillouin zone was used. Calculations were
done using the PBE(n¼6) functional [30], and the numerical
accuracy described therein. With this approach applied to silicates,
the remaining deviations between observed and calculated Raman
shifts have been shown to be very small, with standard deviations
of E3.5 cmꢀ1 and maximum deviation of E10 cmꢀ1 [30].
The basis sets of the atoms were selected as follows: for silicon
a 86-311G(1) contraction [31], and for oxygen a 8-411G(1) contrac-
tion based on the 8-411G contraction given in [32]. For the heavy
atoms Hay and Wadt small core—effective core pseudopotentials
Following the symmetry analysis, there are 78 Raman-active modes,
41 Ag and 37 Bg modes. 81 modes are only IR-active (40 Au, 44 Bu).
2.3.2. Assignment of the Raman bands
In Tables 6 and 7, the observed Raman bands are assigned to the
calculated Raman modes. Symmetry and type of the modes are
derived from the calculation. The assignment was based on the lowest
frequency deviation, taking into account the calculated neighbor
modes and the known accuracy of the method (see Figs. 2 and 3 for
a graphical representation). Many of the Raman-active modes are
close together; therefore a 1:1 mapping is not possible and most of the
observed peaks are composed of several modes.
From the resulting deviations νobs-νcalc, the following statisti-
cal indicators were obtained: for SrSc4(Si2O7)(Si3O10) s¼5.4 cmꢀ1
,

M. Wierzbicka-Wieczorek et al. / Journal of Solid State Chemistry 207 (2013) 94–104
97
Table 2
Ba/Sr, Si1, O1, and O2 atoms are located on mirror planes (y¼1/4).
The O9 atom is located on 0,0,1/2. All remaining atoms are in
general positions.
Fractional atomic coordinates and equivalent isotropic displacement parameters for
BaY4(Si2O7)(Si3O10) (first line), SrYb4(Si2O7)(Si3O10) (second line), and SrSc4(Si2O7)
(Si3O10) (third line). Uequiv according to [23].
The topology of this novel structure type is characterized by
isolated, horseshoe-shaped Si3O10 groups and Si2O7 groups
(Si3O10:Si2O7 ratio¼1:1). These silicate units link zigzag chains,
which are formed by connection of edge-sharing Y1O6 and Y2O6
octahedra; specifically, a non-linear unit with the sequence Y/Yb/
Sc2–Y/Yb/Sc1–Y/Yb/Sc1–Y/Yb/Sc2 forms the backbone of the zig-
zag chains. The zigzag chains can be recognized in views along
both [100] and [001] (Figs. 4 and 5). The [8]-coordinated Ba atoms
are located in narrow channels running parallel to [1 0 0]. The
average Ba–O bond length is 2.88 Å, with individual bond lengths
ranging from 2.684(2) to 3.086(2) Å. The Sr atoms are also bonded
to eight oxygen atoms and show average SrꢀO bond lengths of
2.77 (SrYb-analogue) and 2.71 Å (SrSc-analogue). Average M–O
bond lengths of the Y/Yb/Sc atoms (2.27/2.23/2.12 Å, respectively)
decrease, as expected, with decreasing ionic radius of the M3þ
cations. The bond-valence sums (BVSs) for all atoms are in good
accordance with their theoretical values, except for the Ba and Sr
atoms (Tab. 4). Although the value for Ba (1.72 v.u.) seems low, it is
well-known that the large Ba2þ cation often shows anomalous
BVSs due to a large variability in coordination geometries and
number of ligands [37,2]. Similarly lower values of the BVSs for Sr
are encountered in SrYb4(Si2O7)(Si3O10) and SrSc4(Si2O7)(Si3O10),
in which the sums are substantially less than 2, viz. 1.60 and 1.76 v.
u., respectively. The Sr is clearly underbonded. The energy-
optimized structures from the DFT calculations confirm the under-
bonding of the Ba2þ and Sr2þ cations. The Uequiv values of the
alkaline-earth atoms are within normal ranges (Tab. 2).
The SiꢀSiꢀSi angles in the horseshoe-shaped Si3O10 groups
amount to 93.54(4), 93.15(6), and 95.98(4)1 for BaY4(Si2O7)
(Si3O10), SrYb4(Si2O7)(Si3O10), and SrSc4(Si2O7)(Si3O10), respec-
tively, whereas the SiꢀΟbꢀSi angle in the Si2O7 units is 1801
(symmetry-restricted) (Tab. 4). In the literature, only a few
compounds with narrower SiꢀSiꢀSi angles in the Si3O10 groups
are known, e.g., kinoite, Ca2Cu2[Si3O8(OH)4] ꢀ90.81 [38], thalenite,
(Y,REE)3(OH)[Si3O10] ꢀ86.71 [39], and synthetic K3Yb[Si3O8(OH)2]
ꢀ76.41 [40]. For more details about Si–Si–Si angles in trisilicates
and a comparison to other silicates and non-silicates, the reader is
referred to our recent review [13].
Atom
x
y
z
Uequiv
Ba
Sr
Sr
Y1
Yb1
Sc1
Y2
0.24356(4)
0.24897(10)
0.23211(6)
0.30029(4)
0.29934(3)
0.30363(8)
0.64785(5)
0.65225(3)
0.64087(8)
0.06507(18)
0.0703(3)
0.06244(16)
ꢀ0.22903(13)
ꢀ0.22996(18)
ꢀ0.23540(12)
0.19627(13)
0.19862(18)
0.19765(12)
ꢀ0.1328(5)
ꢀ0.1274(7)
ꢀ0.1492(4)
0.3570(5)
0.3619(7)
0.3630(4)
0.0184(3)
0.0258(5)
0.0222(3)
ꢀ0.3611(4)
ꢀ0.3746(5)
ꢀ0.3889(3)
ꢀ0.1041(3)
ꢀ0.1036(5)
ꢀ0.0929(3)
ꢀ0.4221(3)
ꢀ0.4153(5)
ꢀ0.4215(3)
0.0443(4)
0.0463(6)
0.0283(3)
0.3731(4)
0.3769(5)
0.3850(3)
0.0
1/4
1/4
1/4
0.81524(3)
0.77923(8)
0.77895(5)
0.11818(4)
0.11534(2)
0.11242(6)
0.48159(4)
0.47558(2)
0.46150(7)
0.28224(15)
0.2686(2)
0.25853(14)
0.00708(10)
ꢀ0.00333(15)
ꢀ0.01564(10)
0.59575(11)
0.59578(15)
0.59082(10)
0.4167(4)
0.4062(6)
0.3952(4)
0.4187(4)
0.4128(6)
0.4083(4)
0.1314(3)
0.01040(6)
0.0095(1)
0.00949(8)
0.00611(6)
0.00529(5)
0.00577(9)
0.00636(6)
0.00541(5)
0.00562(9)
0.00506(17)
0.0046(2)
0.00570(16)
0.00510(13)
0.00436(17)
0.00510(11)
0.00670(13)
0.00562(17)
0.00564(12)
0.0076(5)
0.0075(7)
0.0074(4)
0.0078(5)
0.0065(7)
0.0075(4)
0.0088(3)
0.0095(5)
0.0096(3)
0.0093(4)
0.0081(5)
0.0089(3)
0.0080(3)
0.0075(5)
0.0073(3)
0.0088(3)
0.0080(5)
0.0083(3)
0.0173(4)
0.038944(13)
0.040139(8)
0.03805(2)
0.158098(13)
0.158437(8)
0.16003(2)
1/4
Yb2
Sc2
Si1
Si1
Si1
Si2
Si2
Si2
Si3
Si3
Si3
O1
O1
O1
O2
O2
O2
O3
O3
O3
O4
O4
O4
O5
O5
O5
O6
O6
O6
O7
O7
O7
O8
O8
O8
O9
O9
O9
O10
O10
O10
1/4
1/4
0.13604(4)
0.13592(5)
0.13301(3)
0.06040(4)
0.06139(5)
0.06322(3)
1/4
1/4
1/4
1/4
1/4
1/4
0.18356(10)
0.18316(15)
0.18339(8)
0.1740(1)
0.17402(14)
0.17100(8)
0.06357(10)
0.06254(13)
0.05969(8)
0.13034(10)
0.12959(15)
0.12762(8)
0.12809(12)
0.13063(17)
0.13181(8)
0.03356(10)
0.03338(14)
0.03529(8)
0.0
0.1150(4)
0.0993(3)
ꢀ0.2032(3)
ꢀ0.2131(4)
ꢀ0.2332(3)
ꢀ0.0184(3)
ꢀ0.0300(4)
ꢀ0.0335(3)
0.1472(3)
0.1475(4)
0.1444(3)
0.6159(3)
0.6176(5)
0.6022(3)
0.8126(3)
0.8130(4)
0.8184(2)
1/2
0.0142(6)
0.0100(3)
0.0079(3)
0.0076(5)
0.0066(3)
0.0343(10)
0.0256(11)
0.0177(5)
0.0087(4)
0.0091(5)
0.0088(3)
0.0
0.0
0.3685(4)
0.3716(5)
0.3732(3)
0.0
0.0
0.07345(10)
0.07398(15)
0.07539(8)
1/2
1/2
0.4406(3)
0.4373(4)
0.4241(3)
3.1.1. Comparison to related structures
The topology of the new structure type shows some structural
similarities to those of some related phosphates, arsenates, and
silicates already mentioned in the introduction, e.g., NH4Cd6
(P2O7)2(P3O10) [3] and isotypic compounds. These contain layers
based on M2O7 and M3O10 groups (M¼P, As, Si), but with the ratio
2:1. BaY2Si3O10 [7,41] and isotypic compounds BaREE2Si3O10
(REE¼Gd, Er, Yb, Sc) [8,13] contain horseshoe-shaped trisilicate
Si3O10 groups and zigzag chains formed from two REEO6 octahe-
dra. However, no additional Si2O7 disilicate group is present. The
atomic arrangement of NaCa3Mn(V2O7)(V3O10) [1] is not related to
that of the new silicates—it is built from isolated V2O7 and V3O10
groups, which are incorporated into a NaCaMn/O framework. The
cerium germanate Ce24þCe83þ[GeO4]3[Ge2O7]2[Ge3O10] described
by Becker et al. [42] contains three different types of isolated Ge
tetrahedrally coordinated anions and shows also no similarities to
our compounds.
minimum deviation¼ ꢀ9.6 cmꢀ1, maximum deviation¼ þ9.6 cmꢀ1
,
all those observed peaks for which no computed mode could be
assigned, have an intensity o1%; for BaY4(Si2O7)(Si3O10) s¼3.7 cmꢀ1
,
.
minimum deviation¼ ꢀ6.6 cmꢀ1, maximum deviation¼ þ11.5 cm ꢀ1
A few of the observed peaks cannot be assigned at all (e.g., two weak
peaks in the region 790–850 cmꢀ1). These are clearly not Raman
vibrations of the respective phases. The most likely cause of these
peaks is either a thin MoO4 surface layer (flux remnant), microscopic
inclusions of a molybdate phase, or, possibly, fluorescence.
3. Results and discussion
3.1. Crystal structure description
3.2. Measured Raman spectroscopic data, band assignments and
comparison
The asymmetric unit of BaY4(Si2O7)(Si3O10), SrYb4(Si2O7)
(Si3O10), and SrSc4(Si2O7)(Si3O10
Ba/Sr atom, two Y/Yb/Sc atoms, three Si atoms, and ten O atoms.
)
structure-type contains one
During our comprehensive study on new microporous mixed-
framework silicates containing octahedrally coordinated M3þ

98
M. Wierzbicka-Wieczorek et al. / Journal of Solid State Chemistry 207 (2013) 94–104
Table 3
Anisotropic displacement parameters for BaY4(Si2O7)(Si3O10) (first line), SrYb4(Si2O7)(Si3O10) (second line), and SrSc4(Si2O7)(Si3O10) (third line).
Atom
U11
U22
U33
U23
U13
U12
Ba
Sr
Sr
Y1
Yb1
Sc1
Y2
0.00957(10)
0.0084(2)
0.00837(14)
0.00544(11)
0.00516(8)
0.00490(17)
0.00724(11)
0.00631(8)
0.00543(17)
0.0043(4)
0.0044(5)
0.0043(3)
0.0053(3)
0.0055(4)
0.0048(3)
0.0051(3)
0.0051(4)
0.0048(2)
0.0071(11)
0.0052(15)
0.0066(10)
0.0050(11)
0.0058(15)
0.0058(9)
0.0077(8)
0.0078(11)
0.0075(7)
0.0123(9)
0.0099(11)
0.0100(7)
0.0083(8)
0.0068(11)
0.0057(7)
0.0081(8)
0.0086(11)
0.0085(7)
0.0158(10)
0.0114(12)
0.0078(7)
0.0077(8)
0.0071(11)
0.0066(7)
0.037(2)
0.01209(11)
0.0099(2)
0.01078(14)
0.00706(12)
0.00571(8)
0.00685(18)
0.00662(12)
0.00536(8)
0.00613(17)
0.0060(4)
0.0057(6)
0.0070(4)
0.0058(3)
0.0039(4)
0.0057(3)
0.0094(3)
0.0070(4)
0.0070(3)
0.0065(12)
0.0062(16)
0.0076(10)
0.0089(12)
0.0044(15)
0.0082(10)
0.0094(9)
0.0105(12)
0.0103(7)
0.0100(9)
0.0082(12)
0.0100(7)
0.0063(9)
0.0039(11)
0.0062(7)
0.0102(9)
0.0099(12)
0.0098(7)
0.0216(12)
0.0170(15)
0.0105(7)
0.0106(9)
0.0099(12)
0.0084(7)
0.037(2)
0.00977(11)
0.0101(2)
0.0
0.0
0.0
0.00313(8)
0.00243(17)
0.00254(11)
0.00115(8)
0.00110(5)
0.00115(14)
0.00188(8)
0.00174(6)
0.00183(14)
0.0011(3)
0.0007(5)
0.0012(3)
0.0008(2)
0.0014(3)
0.0015(2)
0.0002(2)
0.0007(3)
0.0009(2)
0.0047(9)
0.0040(13)
0.0038(8)
0.0007(9)
0.0018(13)
0.0004(8)
0.0022(7)
0.0021(10)
0.0022(6)
0.0024(7)
0.0021(9)
0.0023(6)
0.0018(6)
0.0020(9)
0.0010(6)
0.0040(7)
0.0045(9)
0.0037(6)
0.0085(8)
0.0059(11)
0.0026(6)
0.0005(6)
0.0023(9)
0.0013(6)
ꢀ0.0008(15)
ꢀ0.0020(19)
ꢀ0.0012(10)
0.0034(6)
0.0045(10)
0.0042(6)
0.0
0.0
0.0
0.00932(15)
0.00558(11)
0.00482(8)
0.00533(19)
0.00528(11)
0.00468(8)
0.00549(19)
0.0048(4)
0.0035(6)
0.0057(4)
0.0039(3)
0.0038(4)
0.0049(3)
0.0048(3)
0.0044(4)
0.0048(3)
0.0104(12)
0.0120(18)
0.0091(11)
0.0088(12)
0.0092(17)
0.0076(10)
0.0092(8)
0.0101(12)
0.0105(8)
0.0054(8)
0.0060(11)
0.0066(7)
0.0092(8)
0.0114(12)
0.0093(7)
0.0091(8)
0.0070(11)
0.0075(7)
0.0169(10)
0.0154(14)
0.0116(8)
ꢀ0.00098(8)
ꢀ0.00095(5)
ꢀ0.00068(13)
ꢀ0.00042(8)
ꢀ0.00042(5)
0.00000(13)
0.0
ꢀ0.00031(8)
ꢀ0.00032(4)
0.00006(13)
ꢀ0.00093(8)
ꢀ0.00091(5)
ꢀ0.00034(13)
0.0
Yb2
Sc2
Si1
Si1
Si1
Si2
Si2
Si2
Si3
Si3
Si3
O1
O1
O1
O2
O2
O2
O3
O3
O3
O4
O4
O4
O5
O5
O5
O6
O6
O6
O7
O7
O7
O8
O8
O8
O9
O9
O9
O10
O10
O10
0.0
0.0
0.0
0.0
0.0001(2)
ꢀ0.0001(3)
0.0001(2)
0.0020(2)
0.0015(3)
0.0004(2)
0.0
0.0
0.0
0.0
0.0
0.0004(2)
0.0001(3)
0.00043(19)
ꢀ0.0012(2)
ꢀ0.0011(3)
ꢀ0.0004(2)
0.0
0.0
0.0
0.0
0.0
0.0
0.0
ꢀ0.0041(7)
ꢀ0.0049(10)
ꢀ0.0040(6)
0.0017(7)
0.0023(10)
0.0016(6)
ꢀ0.0013(7)
0.0007(9)
ꢀ0.0006(5)
ꢀ0.0024(7)
ꢀ0.0024(9)
ꢀ0.0021(6)
0.0064(9)
0.0070(11)
0.0021(6)
0.0000(6)
0.0018(9)
0.0007(5)
0.0023(16)
0.0000(19)
ꢀ0.0008(10)
ꢀ0.0009(7)
ꢀ0.0019(9)
ꢀ0.0005(6)
ꢀ0.0022(7)
ꢀ0.0013(9)
ꢀ0.0028(6)
0.0038(7)
0.0016(10)
0.0024(6)
0.0005(6)
0.0021(9)
0.0001(5)
ꢀ0.0025(7)
ꢀ0.0019(9)
ꢀ0.0024(6)
0.0110(9)
0.0074(11)
0.0027(6)
0.0013(7)
0.0017(9)
0.0013(5)
ꢀ0.0302(18)
ꢀ0.022(2)
ꢀ0.0112(10)
ꢀ0.0015(7)
ꢀ0.0029(10)
ꢀ0.0014(6)
0.0048(8)
0.0060(12)
0.0046(7)
0.0228(18)
0.014(2)
0.0164(13)
0.0050(8)
0.0058(12)
0.0068(7)
0.028(3)
0.030(3)
0.0166(12)
0.0114(9)
0.0108(12)
0.0106(7)
0.0166(12)
0.0103(8)
0.0120(12)
0.0101(7)
cations, we have obtained numerous synthetic sorosilicates and
mixed sorosilicates, including the compounds presented herein.
Thus, we were able not only to measure, for the first time, Raman
spectra of mixed sorosilicates with Si2O7 and Si3O10 groups
[BaY4(Si2O7)(Si3O10) and its two isotypic analogs], but also to
compare them with recently published Raman spectra of chemi-
cally related flux-grown disilicates [14] and additionally measured
Raman spectra of the two previously prepared trisilicates, mono-
clinic BaY2Si3O10 [7] and triclinic SrY2Si3O10 [13] and two new
trisilicates, K2Ca3Si3O10 [43], and CoEu2Si3O10 [44]. The published
Raman spectra of the new, mixed SiO4–Si3O10 silicate mineral
pavlovskyite [Ca8(SiO4)2(Si3O10), 45] and of synthetic α-Y2Si2O7
[46] (a mixed SiO4–Si3O10 silicate) will also be discussed as part of
the comparison. No Raman spectra of mixed Si2O7ꢀSi3O10 silicates
have been previously reported in the literature. However, infrared
(IR) spectra of 17 natural and synthetic silicates including Si3O8
(OH)2 or Si3O10 groups were measured by Povarennykh et al. [47].
These IR spectra of kinoite, kilchoanite, and synthetic Na2Ca3Si3O10
and K3ScSi3O8(OH)2 show a large number of peaks in the range
800–1100 cm ꢀ1
.
Figs. 6 and 7 show the measured Raman spectra of the three
mixed sorosilicates and the two trisilicates, respectively.
Tables 6 and 7 contain both observed and calculated Raman bands
in BaY4(Si2O7)(Si3O10) and SrSc4(Si2O7)(Si3O10). Table 8 lists only
measured band positions in the remaining silicate compounds.
The spectral profiles of the three isotypic mixed sorosilicates are
very similar (Fig. 6). However, the spectrum of BaY4(Si2O7)(Si3O10
)
shows two additional lines at 793 and 840 cmꢀ1, and in SrSc4
(Si2O7)(Si3O10) five additional lines with very low intensities
appear at 615, 640, 762, 809, and 818 cmꢀ1. The DFT calculations
demonstrate that these signals do not correspond to any Raman-
active modes of the crystal structure. All three compounds con-
tain tetrahedral silicate units with one and two non-bridging
oxygen atoms which, according to McMillan [48], would show
the symmetric νs(SiꢀO) stretching vibrations in the region 1100–
1050 cmꢀ1 and 1000–950 cmꢀ1, respectively. In our case, these

M. Wierzbicka-Wieczorek et al. / Journal of Solid State Chemistry 207 (2013) 94–104
99
Table 4
Selected geometric parameters (Å) and calculated bond-valence sums (v.u.) for the coordination polyhedra in BaY4(Si2O7)(Si3O10), SrYb4(Si2O7)(Si3O10), and SrSc4(Si2O7)
(Si3O10).
a
b
b
BaY4(Si2O7)(Si3O10
)
SrYb4(Si2O7)(Si3O10
)
SrSc4(Si2O7)(Si3O10
)
M–O
BVS
M–O
BVS
M–O
BVS
Ba/Sr–O4 (2x)
Ba/Sr–O7 (2x)
Ba/Sr–O2
Ba/Sr–O1
Ba/Sr–O3 (2x)
Mean
2.684(2)
2.832(3)
2.964(3)
2.930(3)
3.086(2)
2.88
0.345
0.231
0.162
0.177
0.116
1.72
2.523(3)
2.672(3)
2.724(4)
2.781(4)
3.150(3)
2.77
0.335
0.224
0.194
0.167
0.061
1.60
2.5304(16)
2.6369(17)
2.711(2)
2.741(3)
2.9339(17)
2.71
0.328
0.246
0.201
0.186
0.110
1.76
Y/Yb/Sc1–O5
Y/Yb/Sc1–O10
Y/Yb/Sc1–O8
Y/Yb/Sc1–O8
Y/Yb/Sc1–O5
Y/Yb/Sc1–O6
Mean
2.2195(19)
2.2434(19)
2.2495(19)
2.2470(19)
2.306(2)
2.340(2)
2.27
0.575
0.538
0.530
0.532
0.454
0.414
3.04
2.192(3)
2.209(3)
2.212(3)
2.222(3)
2.263(3)
2.306(3)
2.23
0.572
0.545
0.541
0.527
0.471
0.420
3.08
2.0813(17)
2.0931(16)
2.0990(16)
2.1143(16)
2.1697(16)
2.2225(16)
2.13
0.534
0.517
0.509
0.489
0.421
0.365
2.83
Y/Yb/Sc2–O7
Y/Yb/Sc2–O4
Y/Yb/Sc2–O10
Y/Yb/Sc2–O6
Y/Yb/Sc2–O1
Y/Yb/Sc2–O2
Mean
2.205(2)
2.2020(19)
2.238(2)
2.2844(19)
2.2951(16)
2.3809(17)
2.27
0.597
0.602
0.546
0.482
0.468
0.371
3.06
2.169(3)
2.179(3)
2.213(3)
2.224(3)
2.272(2)
2.344(2)
2.23
0.608
0.592
0.540
0.524
0.460
0.379
3.10
2.0632(18)
2.0644(17)
2.1066(16)
2.1229(16)
2.1634(14)
2.2296(14)
2.12
0.561
0.559
0.499
0.477
0.428
0.357
2.88
Si1–O1
Si1–O2
Si1–O3 (2x)
Mean
1.620(3)
1.621(3)
1.645(2)
1.63
1.011
1.001
0.945
3.90
1.614(4)
1.622(4)
1.641(3)
1.63
1.027
1.005
0.955
3.94
1.612(2)
1.619(2)
1.6281(17)
1.62
1.033
1.014
0.989
4.02
Si2–O4
Si2–O5
Si2–O6
Si2–O3
Mean
1.606(2)
1.619(2)
1.632(2)
1.678(2)
1.63
1.050
1.014
0.979
0.864
3.91
1.604(3)
1.618(3)
1.633(3)
1.679(3)
1.63
1.055
1.016
0.976
0.862
3.91
1.6033(17)
1.6173(16)
1.6322(17)
1.6651(17)
1.63
1.058
1.019
0.979
0.895
3.95
Si3–O7
Si3–O8
Si3–O9
Si3–O10
Mean
1.620(2)
1.605(2)
1.6203(8)
1.639(2)
1.62
1.011
1.053
1.010
0.960
4.03
1.612(3)
1.618(3)
1.6229(11)
1.637(3)
1.62
1.032
1.016
1.005
0.965
4.02
1.6021(7)
1.6064(17)
1.6300(17)
1.6389(17)
1.62
1.061
1.050
0.984
0.960
4.05
Si2–Si1–Si2′ (1)
Si2–O3b–Si1 (1)c
Si3–O9b–Si3′ (1)d
93.54(4)
136.45 (2x)
180.0
93.15(6)
133.89 (2x)
180.0
95.98(4)
133.55 (2x)
180.0
Bond-valence sums (v.u.) for oxygen atoms of BaY4(Si2O7)(Si3O10), SrYb4(Si2O7)(Si3O10), and SrSc4(Si2O7)(Si3O10): O1¼2.12/2.11/2.07; O2¼1.90/1.95/1.93; O3¼1.92/1.88/1.99;
O4¼2.00/1.98/1.94; O5¼2.04/2.06/1.97; O6¼1.88/1.92/1.82; O7¼1.84/1.86/1.87; O8¼2.11/2.08/2.05; O9¼2.02/2.01/1.97; O10¼2.04/2.05/1.98, respectively.
a
Bond-valence parameters were taken from [24].
Bond-valence parameters for SrꢀO, YbꢀO and SiꢀO were taken from [24] and for ScꢀO from [25] (updated values from www.ccp14.ac.uk/ccp/web-mirrors/
b
i_d_brown).
c
In Si3O10 group.
In Si2O7 group.
d
bands lie in the broader range 1040–780 cmꢀ1. The most intense
Table 5
Observed and calculated unit-cell parameters of SrSc4(Si2O7)(Si3O10) and BaY4
(Si2O7)(Si3O10).
band for all three isotypic compounds is observed within a narrow
range, i.e., at 956 cmꢀ1 for BaY4(Si2O7)(Si3O10), 960 cmꢀ1 for
SrYb4(Si2O7)(Si3O10), and 969 cmꢀ1 for SrSc4(Si2O7)(Si3O10). It is
Parameter
Observed
Calculated
Deviation
Relative deviation (%)
attributed to the symmetric νs(SiꢀO) stretching vibration of the
Si2O7 groups, which is in good agreement with other silicates
containing disilicate groups [48–50]. Bands above 1000 cmꢀ1
[1020 cmꢀ1 in SrSc(Si2O7)(Si3O10), 1038 cmꢀ1 in BaY4(Si2O7)
(Si3O10), and 1040 cmꢀ1 in SrYb4(Si2O7)(Si3O10)] can be caused
by the symmetric SiꢀO stretching vibration (DFT calculations)
or by asymmetric stretching SiꢀOꢀSi vibration [51]. In the litera-
ture, the Raman shifts in the range between 710 and 610 cmꢀ1
were usually ascribed to the symmetric stretching vibration
νs(SiꢀOꢀSi) of Si2O7 groups [44,51–55]. According to Galuskin
et al. [45] this region is composed of a band at 709 cmꢀ1
(theoretical mode) which is caused by a properly stretching
SrSc4(Si2O7)(Si3O10
)
a (Å)
b (Å)
c (Å)
β (1)
5.278
19.221
6.562
106.50
638.3
5.306
19.368
6.596
106.58
649.6
0.028
0.147
0.034
0.08
0.5
0.8
0.5
V (Å3)
11.3
1.8
BaY4(Si2O7)(Si3O10
)
a (Å)
b (Å)
c (Å)
β (1)
5.532
19.734
6.868
106.53
718.8
5.577
19.932
6.920
106.63
736.99
0.045
0.198
0.052
0.102
18.19
0.8
1.0
0.8
V (Å3)
2.5

100
M. Wierzbicka-Wieczorek et al. / Journal of Solid State Chemistry 207 (2013) 94–104
Table 6
Assignment of the observed and calculated Raman-active modes of SrSc4(Si2O7)(Si3O10).
Observed Raman
Relative intensity of
the observed peaks
Calculated Raman
Difference
(Obs)–ν(Calc) (cmꢀ1
)
Symmetry
Typeb
shifts (cmꢀ1
)
shifts (cmꢀ1
)
ν
221
224
240
240
248
267
267
267
276
—
6
4
2
2
3
4
4
4
215.8
232.1
235.6
235.6
242.6
260.5
262.7
263.4
270.9
283.4
288.4
303.2
304.2
321.2
322.9
328.2
335.7
352.7
353.1
355.6
356.8
362.0
365.1
376.8
391.3
393.5
404.1
413.5
434.5
436.5
466.9
471.6
484.9
488.1
501.7
504.8
515.0
519.1
539.6
546.4
555.0
557.2
579.3
598.4
—
Ag
Bg
Bg
Ag
Ag
Bg
Bg
Ag
Ag
Bg
Ag
Ag
Bg
Bg
Ag
Ag
Bg
Bg
Ag
Ag
Bg
Ag
Bg
Ag
Ag
Bg
Bg
Ag
Ag
Bg
Bg
Ag
Bg
Ag
Bg
Ag
Ag
Bg
Bg
Ag
Ag
Bg
Ag
Bg
5.0
-7.9
4.0
4.0
5.7
6.9
4.8
4.0
4.7
—
b(O–Sc–O)
o(O–Sc–O)
b(O–Sc–O)
b(O–Sc–O)
b(O–Sc–O)
o(O–Sc–O)
b(O–Sc–O)
b(O–Sc–O)
b(O–Sc–O)
b(O–Si–O)
b(O–Sc–O)
b(O–Sc–O)
b(O–Sc–O)
b(O–Sc–O)
b(O–Sc–O)
b(O–Sc–O)
b(O–Sc–O)
b(Sc–O–Si)
b(O–Sc–O)
b(Sc–O–Sr)
b(O–Sc–O)
s(O–Sr)
o(O–Sc–O)
b(O–Si–O)
b(Si–O–Sr)
b(Si–O–Sc)
b(O–Sc–O)
s(O–Sc–O)
b(O–Sc–O)
s(O–Sc–O)
b(O–Sc–O)
b(Sc–O–Sc)
b(Si–O–Sc)
b(O–Si–O)
b(O–Si–O)
b(Si–O–Sr)
b(O–Si–O)
b(Si–O–Sc)
b(Si–O–Sc)
b(Si–O–Sc)
b(Si–O–Sc)
b(Si–O–Sc)
b(O–Si–O)
s(Sc–O–Sc)
2
—
—
2
2
8
—
—
295
295
313
313
—
ꢀ7.8
ꢀ8.9
ꢀ7.9
ꢀ9.6
—
8
—
11
—
—
48
48
48
48
14
26
40
40
1
337
—
1.0
—
—
—
361
361
361
361
375
385
400
400
416
426
442
—
5.7
4.5
ꢀ0.7
ꢀ3.8
ꢀ2.1
ꢀ6.5
6.7
ꢀ3.9
2.9
ꢀ8.7
6.0
—
20
6
—
39
—
—
7
7
4
4
—
477
—
5.5
—
—
—
496
509
518
518
—
ꢀ5.7
4.5
3.5
ꢀ0.7
—
547
—
5
—
3
4
1
1
1
5
3
0.7
—
558
581
599
615a
640a
674
686
692
—
0.6
2.1
1.1
—
—
—
669.8
685.4
689.3
716.8
—
Ag
Bg
Ag
Bg
4.3
0.4
2.8
—
b(O–Si–O)
b(O–Si–O)
b(O–Si–O)
s(O–Si)
3
—
a
762
809
818
1
1
1
—
a
—
—
a
—
—
853
867
899
899
913
925
935
944
944
968
968
982
—
1
4
18
18
1
858.5
861.1
890.1
903.6
919.8
927.2
928.0
934.7
934.8
962.6
962.6
975.4
1010.7
1016.6
1059.4
1067.2
Ag
Bg
Ag
Bg
Ag
Bg
Ag
Ag
Bg
Ag
Bg
Ag
Bg
Ag
Ag
Bg
ꢀ6.0
5.6
8.5
ꢀ4.9
ꢀ7.2
ꢀ2.2
7.0
9.6
9.6
5.0
5.0
6.9
—
s(O–Si)
s(O–Si)
s(O–Si)
s(O–Si)
s(O–Si)
s(O–Si)
s(O–Si)
s(O–Si)
s(O–Si)
s(O–Si)
s(O–Si)
s(O–Si)
s(O–Si)
s(O–Si)
s(O–Si)
s(O–Si)
4
2
15
15
100
100
11
—
25
2
1020
1059
—
3.7
ꢀ0.8
—
—
a
No fit with calculated Raman shift.
s—stretching, b—bending, o—other.
b

M. Wierzbicka-Wieczorek et al. / Journal of Solid State Chemistry 207 (2013) 94–104
101
Table 7
Assignment of the observed and calculated Raman-active modes of BaY4(Si2O7)(Si3O10).
Observed Raman
Relative intensity
of the observed peaks
Calculated
Symmetry
Difference ν(Obs)-ν(Calc) (cmꢀ1
)
Typeb
shifts (cmꢀ1
)
Raman shifts (cmꢀ1
)
204
204
204
204
215
229
240
—
8
8
8
8
3
5
2
—
200.5
202.3
206.8
208.1
214.0
227.5
234.4
256.8
260.7
272.1
273.9
282.5
292.0
302.9
309.5
318.4
320.2
326.8
339.8
344.9
350.5
353.5
369.4
388.1
396.8
405.4
422.8
446.5
456.0
462.7
464.4
481.5
483.8
490.1
498.6
524.4
525.9
535.6
537.9
562.5
566.1
640.3
665.3
668.5
694.2
—
Bg
Ag
Bg
Bg
Ag
Ag
Ag
Bg
Ag
Bg
Bg
Ag
Ag
Bg
Ag
Ag
Bg
Bg
Ag
Bg
Bg
Ag
Ag
Bg
Ag
Ag
Bg
Bg
Ag
Bg
Ag
Bg
Ag
Ag
Bg
Bg
Ag
Bg
Ag
Ag
Bg
Ag
Bg
Ag
Bg
3.6
1.8
ꢀ2.7
ꢀ4.0
0.8
2.0
6.0
—
s(Y–Y)
b(O–Y–O)
b(O–Y–O)
b(O–Y–O)
b(O–Y–O)
b(O–Y–Ba)
b(O–Y–O)
b(O–Y–O)
b(O–Y–O)
b(O–Y–O)
b(O–Y–O)
b(O–Y–O)
b(O–Si–O)
b(O–Y–O)
b(O–Y–O)
s(Y–O–Si)
b(O–Y–O)
s(O–Ba)
264
276
276
276
—
3
1
1
1
2.9
4.1
2.2
ꢀ6.4
—
—
300
—
4
—
2
ꢀ3.2
—
315
—
ꢀ3.4
—
—
28
—
17
—
13
15
—
—
39
5
—
—
15
15
—
—
6
—
10
10
8
8
7
7
19
9
327
—
0.5
—
s(O–Ba)
346
—
1.3
—
b(O–Y–O)
s(Y–O–Ba)
s(Y–O–Si)
b(O–Si–O)
b(Si–O–Y)
s(O–Y–O)
b(O–Y–O)
s(O–Y–O)
b(O–Y–O)
b(O–Y–O)
b(O–Si–O)
b(O–Si–O)
b(O–Si–O)
b(O–Si–O)
b(O–Si–O)
o(O–Si–O)
b(Si–O–Y)
b(Si–O–Y)
b(Si–O–Y)
b(Si–O–Y)
b(O–Si–O)
s(Y–O–Y)
b(O–Si–O)
b(O–Si–O)
b(O–Si–O)
s(O–Si)
358
376
—
4.9
6.2
—
—
—
402
429
—
ꢀ3.2
6.6
—
—
—
462
462
—
ꢀ0.9
ꢀ2.7
—
—
—
492
—
2.4
—
527
527
539
539
565
565
642
666
666
706c
793a
840a
863
863
884
893
—
—
1.0
3.2
0.9
2.1
ꢀ1.5
2.5
0.5
ꢀ2.6
11.5
—
9
30
12
9
—
—
14
14
14
47
—
19
19
10
10
100
100
20
9
859.5
865.0
876.2
886.4
915.0
921.1
923.9
938.2
939.5
951.6
957.5
965.3
976.7
977.8
1039.6
1043.4
Ag
Bg
Ag
Bg
Ag
Bg
Ag
Ag
Bg
Ag
Bg
Ag
Bg
Ag
Ag
Bg
4.0
ꢀ1.5
7.5
6.3
—
s(O–Si)
s(O–Si)
s(O–Si)
s(O–Si)
s(O–Si)
s(O–Si)
s(O–Si)
s(O–Si)
s(O–Si)
s(O–Si)
s(O–Si)
s(O–Si)
s(O–Si)
s(O–Si)
s(O–Si)
s(O–Si)
923
923
945
945
956
956
968
982
982
1040
1040
1.8
ꢀ1.0
6.6
5.3
4.6
ꢀ1.3
2.6
5.3
4.2
ꢀ0.1
ꢀ3.9
9
8
8
a
No fit with calculated Raman shift.
s—stretching, b—bending, o—other.
Shoulder.
b
c
(SiꢀO) or as bending (OꢀSiꢀO) or bending (SiꢀOꢀSi) vibration,
and a band at 670 cmꢀ1 which is due to νs(SiꢀOꢀSi) vibrations. In
the disilicate α-Y2Si2O7 [46], which contains Si3O10 trimers and
isolated SiO4 tetrahedra, the strong band at 728 cmꢀ1 has also
been assigned to SiꢀOꢀSi bending vibrations.
Our calculations allow a more sophisticated analysis of the
structural vibrations in this characteristic region, which is very
similar in all three title compounds. In all cases, two strong sharp
lines are observed (at 666 and 642 cmꢀ1 in BaY4(Si2O7)(Si3O10),
and at slightly higher shifts in the other compounds). The nature

102
M. Wierzbicka-Wieczorek et al. / Journal of Solid State Chemistry 207 (2013) 94–104
Fig. 2. Experimental Raman spectrum of BaY4(Si2O7)(Si3O10). The upper bars are
the observed frequencies of bands and the lower bars represent Raman-active
bands calculated with the PBE (n¼6) model.
Fig. 3. Experimental Raman spectrum of SrSc4(Si2O7)(Si3O10). The upper bars are
the observed frequencies of bands and the lower bars represent Raman-active
bands calculated with the PBE (n¼6) model.
Fig. 5. View of BaY4(Si2O7)(Si3O10) along [0 0 1], showing the zigzag/wave-like
connections of the edge-sharing YO6 polyhedra (Si atoms are omitted for clarity).
Fig. 4. View of BaY4(Si2O7)(Si3O10) along [1 0 0], showing zigzag chains and the tri-
and disilicate groups. The unit cell is outlined.
of the modes associated with these lines is the same for both
calculated spectra. The peak at higher shift conforms to two
unresolved modes. Both are characterized by symmetric stretching
of the SiꢀOꢀSi bond of the Si2O7 dimers, around the connecting
oxygen. The character of this mode is dominated by the associated
νb(OꢀSiꢀO) bending, involving all terminal oxygen. The peak at
lower shift comes from a single mode, in which the Si-atoms of the
Si3O10 trimers move symmetrically, so that both SiꢀOꢀSi con-
nections are stretched simultaneously. Again the movement of the
terminal oxygen results in νb(OꢀSiꢀO) bending, too. A fourth
theoretical mode in this region, at higher shifts, results from
asymmetric OꢀSi stretching in the trimer. This mode is not
observed experimentally, though it might be responsible for
the very broad peak in the spectrum of BaY4(Si2O7)(Si3O10).
Fig. 6. Observed Raman spectra of (a) SrSc4(Si2O7)(Si3O10), (b) SrYb4(Si2O7)(Si3O10),
and (c) BaY4(Si2O7)(Si3O10).
These observations are in agreement with the proposition that
the symmetric, simultaneous stretching of the bridging SiꢀO
bonds in the trimer gives rise to strong Raman bands in this
region [45]; the same seems to hold for dimers. If the trimer is in
bent conformation, these movements of the atoms result in
stretching modes and corresponding high frequencies. This is the
case in the title compounds. If the trimers are in linear conforma-
tion, as in α-Y2Si2O7, the strong band has a bending character with

M. Wierzbicka-Wieczorek et al. / Journal of Solid State Chemistry 207 (2013) 94–104
103
interpreted similarly to those of the three mixed sorosilicates. In
SrY2Si3O10 (triclinic) the most intensive, composite bands appears
at ꢃ396 cmꢀ1 and 367 cmꢀ1, which can be attributed to sym-
metric bending modes (OꢀSiꢀO) and (OꢀYꢀO), respectively.
The second strongest band is at 854 cmꢀ1, which can be assigned
to ν1 symmetric SiꢀO stretching vibrations. The spectrum of
(monoclinic) BaY2Si3O10 contains fewer bands (in agreement with
its higher crystal symmetry), and is more like those of the mixed
sorosilicates.
4. Conclusions
In conclusion, we have reported the flux-growth synthesis and
structural characterization of three new isotypic mixed sorosili-
cates, BaY4(Si2O7)(Si3O10), SrYb4(Si2O7)(Si3O10) and SrSc4(Si2O7)
(Si3O10). Their common topology represents a novel chain-based
structure type containing Si2O7 and Si3O10 groups in the ratio 1:1.
The compounds are the first representatives among silicates and
the second among non-silicate (P, As, V) oxycompounds with such
a ratio. The isolated horseshoe-shaped Si3O10 and the symmetry-
restricted Si2O7 groups are located between zigzag chains of MO6
octahedra, while the Ba/Sr cations are located in channels running
parallel to [1 0 0]. Raman spectroscopic investigations of the title
compounds and two chemically related trisilicates have helped to
characterize the vibrational behavior of the silicate units. DFT
calculations show that some of the band assignments proposed in
the literature are incorrect.
Fig. 7. Observed Raman spectra of (a) monoclinic BaY2(Si3O10) and (b) triclinic
SrY2(Si3O10).
Table 8
Observed Raman bands (cmꢀ1) of the one mixed sorosilicates and of the two
trisilicates BaY2Si3O10 (monoclinic) [7] and SrY2Si3O10 (triclinic) [13].
SrYb4(Si2O7)(Si3O10
)
BaY2(Si3O10
)
SrY2(Si3O10)
1021
1005
Shift
1040
997
971a
920
985
971
942
933
890
874
854a
716
699
675
633
559
993
960a
931
893
873
Acknowledgments
873
This work was supported by the Austrian Science Foundation
(FWF) (Grant P17623-N10) and by the Austrian Ministry of Science
BMWF as part of the UniInfrastrukturprogramm of the For-
schungsplattform Scientific Computing at LFU Innsbruck.
669
653
655
References
568
546
535
502
491
464
413
541
545
507
489
453
415
485
[1] R. Rettich, H. Müller-Buschbaum, Z. Naturforsch., B: Chem. Sci. 53 (1999)
507–511.
[2] M. Wierzbicka-Wieczorek, U. Kolitsch, Eur. J. Mineral. (2013), http://dx.doi.org/
10.1127/0935-1221/2013/0025-2289.
[3] Yu.A. Ivanov, M.A. Simonov, N.V. Belov, Dokl. Akad. Nauk SSSR 242 (1978)
599–602.
[4] J. Bennazha, A. El Maadi, A. Boukhari, E.M. Holt, Solid State Sci. 3 (2001)
587–592.
[5] J. Bennazha, A. El Maadi, A Boukhari, E.M. Holt, Acta Crystallogr., Sect. C: Cryst.
Struct. Commun. 58 (2002) i76–i78.
[6] B. Ayed, A.H. Abbdallah, A. Hadded, Acta Crystallogr., Sect. E: Struct. Rep.
Online 60 (2004) i52–i54.
[7] U. Kolitsch, M. Wierzbicka, E. Tillmanns, Acta Crystallogr., Sect. C: Cryst. Struct.
Commun. 62 (2006) i97–i99.
[8] M. Wierzbicka-Wieczorek, (2007) Syntheses, Crystal Structures and Crystal
Chemistry of New Mixed-Framework Silicates and a New Molybdate Structure
Type, Ph.D. Thesis, University of Vienna, 186 pp.
ꢃ473b
418
407
391
380
363
343
324
284
246
231
396a
382
368
379
353
324
306
279
256
227
200
313
278
256
240
226
[9] M. Wierzbicka-Wieczorek, U. Kolitsch, E. Tillmanns, 16th Annual Conference of
the DGK, Erlangen, Germany, March 3–6, 2008; Abstract CD, 2E-01.
[10] M. Wierzbicka-Wieczorek, U. Kolitsch, E. Tillmanns, Cryst. Res. Technol. 43
(2008) 1210–1219.
a
Strongest ones underlined.
Shoulder.
b
[11] M. Wierzbicka-Wieczorek, U. Kolitsch, E. Tillmanns, Acta Chim. Slov. 55 (2008)
909–917.
[12] U. Kolitsch, M. Wierzbicka-Wieczorek, E. Tillmanns, Can. Mineral. 47 (2009)
421–431.
[13] M. Wierzbicka-Wieczorek, U. Kolitsch, E. Tillmanns, Eur. J. Mineral. 22 (2010)
245–258.
[14] M. Wierzbicka-Wieczorek, U. Kolitsch, E. Tillmanns, Can. Mineral. 48 (2010) 51–68.
[15] M. Wierzbicka-Wieczorek, U. Kolitsch, E. Tillmanns, Acta Crystallogr., Sect. C:
Cryst. Struct. Commun. 66 (2010) i29–i32.
the corresponding lower frequencies. Bands between 400 and
560 cmꢀ1 are assigned, according to the DFT data, to νb(OꢀSiꢀO)
symmetric bending modes, which are in good agreement with
many authors (e.g., [43,45,49,56]). Bands below 400 cmꢀ1 are
assigned to vibrations of BaꢀO, SrꢀO, ScꢀO, YꢀO, YbꢀO modes,
and lattice modes.
[16] D. Elwell, Flux growth, in: B.R. Pamplin (Ed.), Crystal Growth. International
Series of Monographs on the Science of the Solid State, Pergamon Press,
Oxford, 1975, pp. 185–216.
[17] W. Tolksdorf, Flux growth, in: D.T.J. Hurle (Ed.), Handbook of Crystal Growth,
North-Holland, Amsterdam, 1994, pp. 563–611.
Differences between the three spectra are due to, first, orienta-
tion of the measured single crystal, and, second, different bond
strengths between tetrahedra and neighboring atoms. The Raman
spectra of the trisilicates BaY2Si3O10 and SrY2Si3O10 (Fig. 7) can be

104
M. Wierzbicka-Wieczorek et al. / Journal of Solid State Chemistry 207 (2013) 94–104
[18] B.M. Wanklyn, Practical aspects of flux growth by spontaneous nucleation, in:
B.R. Pamplin (Ed.), Crystal Growth, Pergamon Press, Oxford, 1975, pp. 217–288.
[19] U. Kolitsch, E. Tillmanns, Mineral. Mag. 68 (2004) 677–686.
[20] Z. Otwinowski, D. Borek, W. Majewski, W. Minor, Acta Crystallogr., Sect. A:
Found. Crystallogr. 59 (2003) 228–234.
[21] G.M. Sheldrick, Acta Crystallogr., Sect. A: Found. Crystallogr. 64 (2008)
112–122.
[22] A.L. Spek, J. Appl. Crystallogr. 36 (2003) 7–13.
[37] I.D. Brown, K.K. Wu, Acta Crystallogr., Sect. B: Struct. Sci. 32 (1976) 1957–1959.
[38] R.B. Laughon, Am. Mineral. 56 (1971) 195–202.
[39] A.N. Kornev, N.G. Batalieva, B.A. Maksimov, V.V. Ilyukhin, N.V. Belov, Dokl.
Akad. Nauk SSSR 202 (1972) 1324–1327.
[40] O.S. Filipenko, G.V. Shilov, L.S. Leonova, N.S. Tkacheva, O.V. Dimitrova, V.
I. Ponomarev, Russ. J. Coord. Chem. 25 (1999) 877–884.
[41] U. Kolitsch, M. Wierzbicka-Wieczorek, E. Tillmanns, 15th Slovenian–Croatian
Crystallographic Meeting, Jezersko, Slovenia, June 15–18, 2006; Book of
Abstracts, 22.
[42] U.W. Becker, J. Felsche, G. Huttner, O. Scheidsteger, Z. Naturforsch., B: Chem.
Sci. 40 (1985) 755–761.
[43] E. Arroyabe, F. Prechtel, D.M. Többens, R. Kaindl, V. Kahlenberg, Eur. J. Mineral.
23 (2011) 425–435.
[44] M. Wierzbicka-Wieczorek, C. Lenz, G. Giester, Eur. J. Inorg. Chem. 19 (2013)
3405–3411.
[23] R.X. Fischer, E. Tillmanns, Acta Crystallogr., Sect. C: Cryst. Struct. Commun. 44
(1988) 775–776.
[24] N.E. Brese, M. O′Keeffe, Acta Crystallogr., Sect. B: Struct. Sci. 47 (1991) 192–197.
[25] I.D. Brown, J. Appl. Crystallogr. 29 (1996) 479–480.
[26] L.M. Gelato, E. Parthé, J. Appl. Crystallogr. 20 (1987) 139–143.
[27] Shape Software, ATOMS for Windows and Macintosh. Version 5.0.4. Shape
Software, Kingsport, Tennessee, USA (1999).
[28] R. Dovesi, V.R. Saunders, C. Roetti, R. Orlando, C.M. Zicovich-Wilson, F. Pascale,
B. Civalleri, K. Doll, N.M. Harrison, I.J. Bush, Ph. D'Arco, M. Llunell, CRYSTAL09—
A Computational Tool for Solid State Chemistry and Physics, University of
Turin, Italy, 2009.
[29] F. Pascale, C.M. Zicovich-Wilson, F. Lopez, B. Civalleri, R. Orlando, R. Dovesi, J.
Comput. Chem. 25 (2004) 888–897.
[30] D.M. Többens, V. Kahlenberg, Vib. Spectrosc. 56 (2011) 265–272.
[31] F. Pascale, C.M. Zicovich-Wilson, R. Orlando, C. Roetti, P. Ugliengo, R. Dovesi, J.
Phys. Chem. B 109 (2005) 6146–6152.
[32] M.D. Towler, N.L. Allan, N.M. Harrison, V.R. Saunders, W.C. Mackrodt, E. Apra,
Phys. Rev. B: Condens. Matter 50 (1994) 5041–5054.
[45] E.V. Galuskin, F. Gfeller, V.B. Savelyeva, T. Armbruster, B. Lazic, I.O. Galuskina,
D.M. Többens, A.E. Zadov, P. Dzierzanowski, N.N Pertsev, V.M. Gazeev, Am.
Mineral. 97 (2012) 503–512.
[46] V. Kahlenberg, W. Wertl, D.M. Többens, R. Kaindl, P. Schuster,
H. Schottenberger, Z. Anorg. Allg. Chem. 634 (2008) 1166–1172.
[47] A.S. Povarennykh, B.N. Litvin, M. Bednar, Geol. Zh. (Russian Ed.) 36 (1976)
76–85. (in Russian).
[48] P. McMillan, Am. Mineral. 69 (1984) 622–644.
[49] R.L Frost, J.M. Bouzaid, B.J. Reddy, Polyhedron 26 (2007) 2405–2412.
[50] J.-L. You, G.-C. Jiang, H.-Y. Hou, H. Chen, Y.-Q. Wu, K.-D. Xu, J. Raman Spectrosc.
36 (2005) 237–249.
[33] P.J. Hay, W.R. Wadt, J. Chem. Phys. 82 (1985) 270–283.
[34] CRYSTAL Basis Sets Library, 2006, 〈http://www.crystal.unito.it/Basis Sets/
Ptable.html〉 (last accessed: 2010).
[35] T. Bredow, K. Jug, R.A. Evarestov, Phys. Status Solidi B 243 (2006) R10–R12.
[36] S. Piskunov, E. Heifets, R.I. Eglitis, G. Borstel, Comput. Mater. Sci. 29 (2004)
165–178.
[51] S.K. Sharma, B. Simons, H.S. Yoder Jr., Am. Mineral. 68 (1983) 1113–1125.
[52] M. Gabelica-Robert, J. Mol. Struct. 79 (1982) 255–260.
[53] P. Tarte, M.J. Pottier, A.M. Procès, Spectrochim. Acta, Part A 6 (1973) 1017–1027.
[54] M.E. Fleet, G.S. Henderson, Phys. Chem. Miner. 24 (1997) 345–355.
[55] S.A. Markgraf, S.K. Sharma, A.S. Bhalla, J. Mater. Res. 8 (1993) 635–648.
[56] H. Poulet, J.P. Mathieu, Bull. Soc. Fr. Minéral. Cristallogr. 98 (1975) 3–5.