Hydrothermal synthesis and crystal structures of Li,Ba-nanoborate, LiBaB9O15, and Ba-borophosphate, BaBPO5

Article abstract of DOI:10.1016/S0925-8388(01)02017-5

The crystal structure determination of lithium and barium nanoborates synthesized under hydrothermal conditions was reported. The structure of BaBPO₅ was refined by Rietveld method in contrast to the structure of PbBAsO₅, which was determined on a single crystal. The phase transformation at high temperature in the stillwellite structure type accompanied by the replacement of the polar space group was also reported. The phase expansion of the La-polyhedron was compared to BO₄ and GeO₄ tetrahedra.

Full text of DOI:10.1016/S0925-8388(01)02017-5

Journal of Alloys and Compounds 339 (2002) 70–75
L
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Hydrothermal synthesis and crystal structures of Li,Ba-nanoborate,
LiBaB O , and Ba-borophosphate, BaBPO
9
15
5
a ,
a
b
b
a
*
D.Yu. Pushcharovsky , E.R. Gobetchia , M. Pasero , S. Merlino , O .V . Dimitrova
a
Geology Department, Moscow State University, 119899 Moscow, Russia
Department of Earth Sciences, University of Pisa, via Santa Maria 53, 56126 Pisa, Italy
b
Received 2 November 2001; accepted 11 December 2001
Abstract
Two compounds Li,Ba-nanoborate LiBaB O (I) and Ba-borophosphate BaBPO (II) were synthesized in the hydrothermal systems
9
15
5
BaCl –Li CO –B O –H O and BaO–B O –P O –H O (T5280 8C, P5100 bar, 20 days). The crystal structures of I and II were
2
2
3
2
3
2
2
3
2
5
2
3
¯
˚
˚
established from X-ray single crystal diffraction: (I) space group R3c, a510.982(2), c517.067(3) A, V51782.6(5) A , R 50.033 for
47 uF u . 4s(F ); (II) space group P3 2, a57.114(1), c56.993(1) A, V5306.49(8) A , R 50.0252 for 576 uF u $ 4s(F ). While (II)
hkl
3
˚
˚
3
o
o
2
hkl
o
o
is isotypic to the stillwellite, LiBaB O represents a completely novel type of crystal structure. It comprises a borate framework with
9
15
tunnels filled by Ba atoms in 12-fold coordination and by Li atoms in unusual 3-fold coordination.
rights reserved.
 2002 Elsevier Science B .V . All
Keywords: Optical materials; Chemical synthesis; Crystal structure; X-ray diffraction
1
. Introduction
due to the perspectives of exploring new functional
materials which exhibit non-linearity in optical properties.
The crystal structure and the results of thermal de-
The study of synthetic Li,Ba-nanoborate LiBaB O is
9
15
part of a program on the crystal chemistry of lithium and
barium borates that includes structure determination of
phases obtained under hydrothermal conditions. The
reason of search for new borates is the relationship
between crystal structure and optical properties of non-
linear optical materials—alkaline and alkaline-earth bo-
composition studies of BaBPO were recently reported in
Ref. [9]. Similarly to CaBPO5 and SrBPO5 [7], the
5
structure of BaBPO was refined by the Rietveld method
5
in the space group P3 2 in contrast to the structure of the
1
chemically related PbBAsO which was determined on a
5
single crystal to belong to space group P31 [10]. It is
rates. Five Li,Ba-borates, namely Li Ba B O
[1],
worthy to note that the c parameter of BaBPO according
6
2
4
11
5
LiBa B O [1,2], LiBaB O , synthesized by solid state
to data in Ref. [9] should be two times smaller as
compared with that reported in Ref. [11]: 6.990 vs. 13.977
2
5
10
9
15
reaction [3], LiBaBO3 [4] and LiBa [B O (OH) ] [5]
2
10 16
3
˚
have been reported sofar. The crystal structures of
LiBa B O [2], LiBaBO [4] and LiBa [B O (OH) ]
A. Apart from that, the relatively high values of R 50.084
p
and Rwp 50.123, of the thermal displacement parameter for
2
5
10
3
2
10 16
3
[
5] are already known whereas the crystal structure of
the P atom and the unusual set of interatomic distances
˚
LiBaB O is described herein.
B–O (1.338–1.604 A) in the BO tetrahedra [9], prompted
9
15
4
Ba-borophosphate BaBPO5 belongs to the stillwellite,
us to reinvestigate the crystal structure of BaBPO . The
5
CeBSiO , structural type, which comprises a large group
results of this work are reported below.
5
2
1
51
of compounds with general formula M BX O , where
5
2
1
51
M
5Ca, Sr, Ba and X 5P, As. Some other borophos-
phates are also known, namely Zn BPO , Mg BPO [6],
2. Experimental
3
7
3
7
Ba [(PO ) BPO ] [7] and Pb [(PO ) BPO ] [8]. The
3
4
2
4
3
4
2
4
interest in their synthesis and characterization is mainly
Colourless transparent single crystals of Li,Ba-nanobo-
rate LiBaB O
and Ba-borophosphate BaBPO5 were
9
15
*
Corresponding author.
synthesised in the hydrothermal (T5280 8C, P5100 bar)
E-mail address: dmitp@geol.msu.ru (D.Yu. Pushcharovsky).
systems BaCl –Li CO –B O –H O (BaCl /Li CO /
2
2
3
2
3
2
2
2
3
0
925-8388/02/$ – see front matter
 2002 Elsevier Science B .V . All rights reserved.
PII: S0925-8388(01)02017-5

D.Yu. Pushcharovsky et al. / Journal of Alloys and Compounds 339 (2002) 70–75
71
B O 52:1:2) and BaO–B O –P O –H O (BaO/B O /
system according to the ellipsoid approximation and
reduced to uFu . The software package SHELX-97 [13]
2
3
2
3
2
5
2
2
3
2
P O 51:1:1), respectively. In the experiments which
2
5
resulted in the synthesis of the Ba-borophosphate BaBPO5,
the starting materials were put into autoclaves which
contained a small amount of HCl (0.5 M) as a solvent. The
duration of the syntheses was 20 days. The crystals of
Li,Ba-nanoborate have isometric habits and those of Ba-
borophosphate can be described as elongated plates with a
maximal size of 1 mm. The identification of both phases
was carried on through a X-ray powder diffraction study.
The experimental data were collected on an ADP-2
diffractometer (Cu Ka radiation, l51.54056, Ni-filter;
was used in the structure determination. The figures were
obtained with the use of the program ATOMS [14].
2.1. LiBaB O
9
15
The unit cell parameters were derived through a least
squares fit using 24 medium u reflections 10.5,2u ,24.48.
The crystal structure determination by direct methods and
¯
refinement were performed in space group R3c, using 347
reflections with I . 2s(I). The E synthesis presented a
peak which was assumed as due to the Ba atom. Its
position was refined in an isotropic approach and a
subsequent synthesis allowed to locate the O atoms and
part of the B atoms. The structure determination has been
completed with a Dr synthesis. Thus the formula of the
compound, LiBaB O , has been established as a result of
5
.008,2u ,80.008; 2u scan with steps of 0.028; the
exposure time per step, 5 s). The comparison of the powder
diffraction patterns with the ICDD data base [12] revealed
similarity of the synthesised phases with Li,Ba-nanoborate
LiBaB O
and with Ba-borophosphate BaBPO . The
9
15
5
qualitative electron probe microanalysis using a SEM
Philips PW 6800/70 with EDS electron probe, proved the
presence of Ba as the main element in both phases.
Two sets of intensity data were obtained on a Siemens
P4 four circle diffractometer using graphite monochromat-
9
15
its structural investigation. The refinement of the structure
with anisotropic displacement parameters for all atoms
decreased the R factor to 0.033 for 347 uF u . 4s(F ) and
o
o
2
to 0.0478 for all 458 data; wR (F ) 5 0.0787. Refined
atomic coordinates and interatomic distances are given in
Tables 2 and 3. The final electron density map was
˚
ized Mo Ka radiation (l50.71073 A). The intensity of
three standard reflections measured every 97 observations
did not show fluctuations larger than 3%. The experimental
details of the data collection are given in Table 1. All
intensities were corrected for absorption by an c-scan
2
3
˚
featureless: maximum Dr51.44 e A , minimum Dr5
21.12 e A . The bond-strength values, calculated accord-
2
3
˚
ing to Ref. [15], are presented in Table 4.
Table 1
Experimental details of the structure determinations of LiBaB O and BaBPO5
9
15
Formula
LiBaB O
BaBPO5
9
15
Cell weight
Crystal system
Space group; Z
Unit cell dimensions (A)
Unit cell volume (A )
2889.31
Trigonal
R3c; 6
a510.982(2), c517.067(3)
1782.6(5)
777.32
Trigonal
¯
P3 2; 2
2
˚
a57.114(1), c56.993(1)
306.49(8)
3
˚
F (000)
Density (calc.) (g cm
Linear absorption coefficient (mm
Radiation; l (A)
1344
2.69
3.43
Mo Ka; 0.71073
348
4.21
10.01
Mo Ka; 0.71073
2
3
)
2
1
)
˚
Crystal size (mm)
Diffractometer
Scan type
0.1230.1030.12
Siemens P4
u–2u
0.1030.1030.16
Siemens P4
u–2u
2u range (8)
6.42–55
6.62–59.95
Indices range
21#h#13, 214#k#1, 222#l#1
29#h#9, 210#k#10, 29#l #9
Collected reflections
1224
1289
Unique reflections
458
586
R(int) from merging equivalents
Criterion for significance
Absorption correction
Structure refinement
Number of refined parameters
R1 (conventional R factor)
0.0572
I . 2s(I)
c-scan
Full-matrix least squares
42
0.0519
I . 2s(I)
c-scan
Full-matrix least squares
40
0.0257 for all 586 data;
0.0252 for 576 F . 4s(F )
0.0773
0.0480 for all 458 data;
0
.0330 for 347 F . 4s(F )
o o
o
o
2
wR2 (weighted R on on F )
0.0862
S (goodness of fit)
1.050
0.572
Program
SHELX-97 [13]
SHELX-97 [13]

7
2
D.Yu. Pushcharovsky et al. / Journal of Alloys and Compounds 339 (2002) 70–75
Table 2
Fractional atomic coordinates and equivalent displacement parameters U
(
Table 4
Bond–valence parameters for LiBaB O [15]
eq
9
15
2
˚
in A ) for LiBaB O
9 15
Atom
O1
O2
O3
–
Scations
Atom
x/a
y/b
z/c
Ueq
[36]
[36]
Ba
B1
B2
Li
Sanions
0.128
1.070
0.745
–
0.192
1.058
0.771
–
1.920
3.030
3.032
0.960
–
[
32]
Ba
B1
B2
Li
O1
O2
O3
0
0
0
0.0162(3)
0.014(1)
0.011(1)
0.09(2)
0.0138(6)
0.0148(7)
0.0167(10)
0.902
[
32]
[32]
0.2681(5)
1/3
1/3
0.2263(3)
0.2521(4)
0
0.8699(5)
0.0974(6)
2/3
0.1148(3)
0.9837(3)
0.1719(4)
0.9784(3)
11/12
11/12
0.8732(2)
0.9726(2)
1/4
–
[
33]
0.320
2.124
1.943
2.021
Left and right superscripts indicate the number of equivalent bonds for
anions and cations, respectively.
Table 5
Fractional atomic coordinates and equivalent displacement parameters U
eq
2
.2. BaBPO5
The unit cell parameters were derived by a least-squares
2
˚
(
in A ) for BaBPO
5
Atom
x/a
y/b
0.39502(6)
z/c
Ueq
fit using 32 medium u reflections 13,2u ,228. The crystal
structure determination and refinement were performed in
space group P3 2. After merging, R50.0252 for 576
uF u $ 4s(F ) and R50.0257 for all 586 independent
reflections. Refined atomic coordinates and interatomic
distances are given in Tables 5 and 6. The final electron
density map was featureless: maximum Dr 5 1.82 e A
minimum Dr521.50 e A . A bond–valence analysis is
presented in Table 7.
Ba
P
B
O1
O2
O3
0
1/3
1/6
1/3
20.0379(7)
20.0350(7)
5/6
0.0092(2)
0.0077(4)
0.010(2)
0.0104(9)
0.0156(10)
0.0109(11)
0.3896(3)
0
0.1395(7)
0.8562(8)
0
0
20.093(2)
0.3230(7)
0.4274(8)
20.0411(9)
2
o
o
2
3
˚
,
2
3
˚
Considering that the structures of natural stillwellites
were described in the polar axial space group P3 , the
1
have the general formulas REE[BSiO ] (REE5Ce, La
structure of BaBPO was also refined in P3 up to R5
5
5
2
(
dominant), Pr, Nd, Th) [16,17] and that some of their
0.0398 for 1048 uF u $ 4s(F ) and 0.0407 for all 1069
o
o
synthetic analogues, namely PbBAsO [8], LaBGeO [18],
independent reflections. The assumption of twinning did
5
5
Table 3
˚
Interatomic distances (A) for LiBaB O
9
15
Barium polyhedron
Boron polyhedra
Lithium polyhedron
a
m
n
Ba–O2
2.900(3)
2.900(3)
2.900(3)
2.900(3)
2.900(3)
2.900(3)
3.052(3)
3.052(3)
3.052(3)
3.052(3)
3.052(3)
3.052(3)
B1–O1
–O2
–O3
1.346(5)
1.350(6)
1.409(5)
Li–O3
–O3
1.888(5)
1.888(5)
1.888(5)
b
c
d
e
f
r
–
–
–
–
–
–
–
–
–
–
–
O2
O2
O2
O2
O2
O1
O1
O1
O1
O1
O1
n
s
–O3
kB1–Ol
1.368
kLi–Ol
1.888
g
h
i
o
B2–O2
1.467(5)
1.467(5)
1.480(5)
1.480(5)
p
–O2
–O1
–O1
j
q
k
l
kB2–Ol
1.473
kBa–Ol
2.976
Symmetry code
a: x 2 y 1 1, x, 2 z 1 1
b: 2 x 1 y 2 1, 2 x, z 2 1
c: y 2 1, 2 x 1 y 2 1, 2 z 1 1
d: 2 y 1 1, x 2 y 1 1, z 2 1
e: x, y 2 1, z 2 1
h: x 2 y, x, 2 z 1 1
i: 2 y, x 2 y, z 2 1
j: y, 2 x 1 y, 2 z 1 1
k: x, y, z 2 1
o: x, y 2 1, z
p: 2 x 1 2/3, 2 x 1 y 2 2/3, 2 z 1 11/6
q: 2 x 1 2/3, 2 x 1 y 1 1/3, 2 z 1 11/6
r: 2 y 1 1/3, x 2 y 1 2/3, z 1 2/3
s: 2 x 1 y 1 1/3, 2 x 1 2/3, z 1 2/3
l: 2 x, 2 y, 2 z 1 1
f: 2 x, 2 y 1 1, 2 z 1 1
g: 2 x 1 y, 2 x, z 2 1
m: 2 x 1 y 1 1/3, y 1 2/3, z 1 1/6
n: x 1 1/3, y 1 2/3, z 1 2/3

D.Yu. Pushcharovsky et al. / Journal of Alloys and Compounds 339 (2002) 70–75
73
Table 6
˚
Interatomic distances (A) for BaBPO
5
Barium polyhedron
Phosphorus polyhedron
Boron polyhedron
a
h
g
Ba–O2
2.666(5)
2.666(5)
2.823(3)
2.823(5)
2.901(4)
2.901(4)
2.915(5)
2.915(5)
2.919(5)
2.919(5)
P–O2
1.497(5)
1.497(5)
1.578(4)
1.578(4)
B–O3
–O3
1.439(6)
1.439(6)
1.523(9)
1.523(9)
b
i
f
l
j
–
–
–
–
–
–
–
–
–
O2
O2
O2
O1
O1
O1
O1
O3
O3
–O2
–O1
–O1
c
d
a
b
j
–O1
–O1
k
kP–Ol
1.537
kB–Ol
1.481
e
f
h
i
g
f
l
j
O2 –O2
O2 –O1
O2 –O1
O2 –O1
O2 –O1
O1 –O1
2.556(10)
2.472(6)
2.527(6)
2.472(6)
2.527(6)
2.490(9)
O3 –O3
O3 –O1
O3 –O1
O3 –O1
O3 –O1
O1 –O1
2.385(6)
2.436(7)
2.454(4)
2.436(7)
2.454(4)
2.322(8)
h
j
g
g
h
k
g
i
j
f
l
i
k
f
j
kBa–Ol
2.845
j
k
l
j
kO–Ol
2.507
kO–Ol
2.415
Symmetry code
a: 2 x 1 y, 2 x 1 1, z 1 1/3
b: x 2 y, 2 y 1 1, 2 z 1 1/3
c: x 2 1, y, z
e: 2 x, 2 x 1 y, 2 z 1 2/3
f: 2 x 1 y, 2 x, z 2 2/3
g: 2 y, x 2 y, z 2 1/3
i: y, x 2 1, 2 z
j: 2 x 1 y, 2 x, z 1 1/3
k: y, x, 2 z
d: 2 x 1 1, 2 x 1 y 1 1, 2 z 1 2/3
h: 2 x 1 y 1 1, 2 x 1 1, z 1 1/3
l: x 2 y, 2 y, 2 z 1 1/3
not improve the R factor and indicated that the volume of
the second individual is close to 0. Thus the space group
and larderellite presents the same FBB 4n1h connected to
build an infinite chain. So ameghinite is the only natural
borate presenting FBB 2n1h. The scheme given below
reproduces the structure of the FBB 2n1h, with three
P3 2 reported previously for the structures of alkaline
2
2
1
21
earth stillwellites, M BPO (M 5Ca, Sr) [7] and for
5
HT form of LaBGeO [18] was confirmed.
oxygen atoms (O ) linked to two B atoms and four
5
br
oxygen atoms (Onbr) linked to only one B atom (‘free’
vertices of the FBB unit) (Fig. 3). In the crystal structure
3
. Discussion
3
.1. LiBaB O
9
15
The structure contains a three-dimensional borate frame-
work, formed by B(1)O triangles and B(2)O tetrahedra
3
4
(
Figs. 1 and 2). Three-membered polyhedral rings (2n1h)
composed of two BO triangles and one BO tetrahedron
3
4
can be considered as a fundamental building block (FBB)
19] within the framework. This kind of FBB form the
[
finite clusters in the structures of ameghinite, sborgite, and
ammonioborite. Infinite chains based on similar type of
FBB were revealed in the larderellite.
As a matter of fact the FBB unit appears as finite cluster
only in the structure of ameghinite, because sborgite and
ammonioborite are based on the FBB 4n1h (two 3-
membered rings 2n1h share the same BO tetrahedron)
Fig. 1. Projection of LiBaB O on (001).
4
9
15
Table 7
Bond–valence parameters for BaBPO5 [15]
Atom
O1
O2
O3
Scations
[
32]
[32]
[32]
[32]
[32]
[32]
[32]
[32]
Ba
P
B
Sanions
0.192 10.185
0.362
1.335
–
10.237
0.183
0.832
2.318
4.816
2.990
–
[
[
32]
32]
1.073
0.663
2.113
–
[32]
1.934
2.030
Left and right superscripts indicate the number of equivalent bonds for anions and cations, respectively.

7
4
D.Yu. Pushcharovsky et al. / Journal of Alloys and Compounds 339 (2002) 70–75
Fig. 4. Crystal structure of BaBPO5 as seen along [001].
˚
interatomic distances Li–O(3) of 1.888 A. The LiO
Fig. 2. The crystal structure of LiBaB O15, perspective view..
3
9
triangles with similar Li–O distances were already re-
vealed in a series of metalloorganic compounds, namely in
bicyclic structures of lithium ester enolates [20], in
homoleptic titanium (III) thiolate complexes [21], and in
lithium borylamide salts [22]. This kind of co-ordination is
also anticipated for Li in the structure of bikitaite heated at
temperatures higher than 480 8C [23].
of Li,Ba-nanoborate each free vertex is linked to another
FBB; in particular the two free vertices of the tetrahedron
are linked to triangular B of adjacent FBBs, whereas the
two free vertices of the triangles are linked to tetrahedral B
of adjacent FBBs. In summary, each FBB has the formula
B O[br]3O[nbr]4 with the four non-bridging oxygens being
3
common to two adjacent FBB and therefore counting for
half. As a consequence, the stoichiometry of the frame-
work is B O O , namely B O as it appears in the formula
3
.2. BaBPO5
3
3
2
3
5
Similar to all stillwellite-like compounds, the main
of the compound LiBaB O .
9
15
structural elements of BaBPO are spiral tetrahedral chains
5
The borate framework in LiBaB O contains large
9
15
[001] (Figs. 4 and 5) built of three-membered rings. The
tunnels parallel to [001], filled by Ba and Li cations which
contacts between the BO tetrahedra that form the central
part of these chains are reinforced by PO tetrahedra and
thus [BPO ] heterotetrahedral chain complexes are pro-
duced. Like many other structures which contain complex
chains formed by chemically different tetrahedra (for
example, euclase, v a¨ ryrynenite, hellandite etc.) the tetra-
hedra of cations with higher valence can be considered as
¯
4
alternate along the 3 inversional axes. The Ba atoms are
4
located in typical 12-fold polyhedra whereas the Li atoms
are within unusual triangles formed by O(3) atoms with
5
the ‘branches’. Spiral chains formed by BO tetrahedra,
4
screwing along the 3 axis, provide the linkage between
2
the columns along [001] composed of Ba 10-fold poly-
hedra alternated with PO tetrahedra. This kind of columns
4
formed by alternating large cation polyhedra and tetrahedra
2
2
Fig. 3. The FBB composed of two BO3 triangles and one BO4 tetra-
Fig. 5. The heterotetrahedral chain [BPO5] , running parallel to [001],
hedron in the crystal structure of LiBaB O15.
in BaBPO5.
9

D.Yu. Pushcharovsky et al. / Journal of Alloys and Compounds 339 (2002) 70–75
75
[
2] Q. Huang, L. Shaofang, D. Guiqin, J. Liang, Acta Crystallogr. 48
were revealed in the structures of rhabdophane, xenotime,
zircon, anhydrite and garnet.
(
1992) 1576–1578.
[3] Y.-C. Song, Z.-K. Huang, Mater. Lett. 12 (1991) 363–368.
The possible phase transformation at high temperature in
the stillwellite structure type which is accompanied by the
replacement of the polar space group P3 (3 ) by P3 2 was
[4] M. Schlaeger, R. Hoppe, Z. Anorg. Allg. Chem. 619 (1993) 976–
9
82.
[5] D.Yu. Pushcharovsky, S. Merlino, O. Ferro, S.A. Vinogradova, O .V .
Dimitrova, J. Alloys Comp. 306 (2000) 163–169.
1
2
1
reported in Ref. [17]. Later on it was confirmed by the
results of high-resolution neutron powder diffraction of
LaBGeO5 [18] which adopts at 530 8C the space group
[
[
6] J. Liebertz, S. St a¨ hr, Z. Kristallogr. 160 (1982) 135–137.
7] R. Kniep, G. G o¨ zel, B. Eisenmann, C. R o¨ hr, M. Asbrand, M.
Kizilyalli, Angew. Chem. Int. Ed. Engl. 33 (1994) 749–751.
P3 2. During the heating of this phase the expansion of the
1
[8] Ch.-H. Park, K. Bluhm, Z. Naturforsch. B 50 (1995) 1617.
[9] Y. Shi, J. Liang, H. Zhang, Q. Liu, X. Chen, J. Yang, W. Zhuang, G.
Rao, J. Solid State Chem. 135 (1998) 43–51.
La-polyhedron is higher compared to BO4 and GeO4
tetrahedra and the 9-fold coordination of La is replaced by
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[11] H. Bauer, Z. Anorg. Allg. Chem. 345 (1966) 225–229.
[12] JCPDS, PCPDFWIN: A Windows Retrieval/Display Program for
Accessing the ICDD PDF-2 Database, International Center for
Diffraction Data, 1998.
a 10-fold coordination in the HT form. In this connection,
the crystallization of BaBPO5 with even bigger BaO10
polyhedra in space group P3 2 does not look completely
2
unusual.
[
13] G.M. Sheldrick, SHELX-97: Program for the Solution and Refine-
ment of Crystal Structures, Siemens Energy and Automation,
Madison, WI, 1997.
Acknowledgements
[14] E. Dowty, Atoms 3.2. A Computer Program for Displaying Atomic
Structures, Kingsport, Tennessee 37663, 1995.
This work was supported in part by the Russian Sci-
entific Foundation (grants 00-05-65399 and 00-15-96633),
and by the Russian Universities Programme. S. Merlino
acknowledges the support of MURST, through a grant to
the national project ‘Structural complexity and mineral
properties: microstructures, modularity, modulations’. A
grant for a research stay in Pisa (project 62, enclosure 6:
[
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[16] A. Callegari, G. Giuseppetti, F. Mazzi, C. Tadini, N. Jb. Miner. Mh.
H 2 (1992) 49–57.
[
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731–762.
‘Crystal structures and topology of rare and new minerals’
within the frame of the agreement for scientific and
technological cooperation between Italy and Russia) is
gratefully acknowledged.
[20] J.L. Garcia Ruano, D. Barros, M.C. Maestro, R. Araya-Maturana, J.
Fischer, J. Org. Chem. 61 (1996) 9462–9470.
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[
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