BaCo2(AsO4)2

Đordević, T.

doi:10.1107/S1600536808025865

inorganic compounds

CRYSTALLOGRAPHIC
COMMUNICATIONS

ISSN: 2056-9890

Volume 64| Part 9| September 2008| Pages i58-i59

doi:10.1107/S1600536808025865

Open

access

BaCo₂(AsO₄)₂

Tamara Đordević ^a ^*

^aInstitut für Mineralogie und Kristallographie, Universität Wien-Geozentrum, Althanstrasse 14, A-1090 Vienna, Austria
^*Correspondence e-mail: tamara.djordjevic@univie.ac.at

(Received 6 August 2008; accepted 11 August 2008; online 16 August 2008)

Suitable single crystals of the title compound, barium dicobalt(II) bis[orthoarsenate(V)], were prepared under hydrothermal conditions. This phase belongs to a series of compounds with general formula AM₂(XO₄)₂, where A = alkaline earth metal, M = Mg or a divalent first-row transition element, and X = P, As or V. BaCo₂(AsO₄)₂ is isotypic with BaNi₂(XO₄)₂ (X = P, V or As) and is characterized by brucite-like sheets of edge-sharing CoO₆ octahedra (3 symmetry) parallel to (001), with one-third of the octahedral positions being vacant. The sheets are capped above and below by AsO₄ tetrahedra (3 symmetry) and are interconnected by distorted BaO₁₂ cuboctahedra ( $[\overline{3}]$ symmetry).

Related literature

For isostructural compounds, see: Eymond et al. (1969a ,b ); Bircsak & Harrison (1998 ); El-Bali et al. (1999 ); Faza et al. (2001 ); Rogado et al. (2002 ); Wichmann, & Müller-Buschbaum (1984 ). For magnetic properties of BaCo₂(AsO₄)₂, see: Dojčilović et al. (1994 ); Regnault et al. (2006 ). For related compounds, see: Effenberger & Pertlik (1993 ); El-Bali et al. (1993a ,b ); Hemon & Courbion (1990 ); Kreidler & Hummel (1961 ); Lucas et al. (1998 ); Mihajlović et al. (2004 ); Moquine et al. (1993 ); Osterloh & Müller-Buschbaum (1994 ). For general background, see: Brese & O'Keeffe (1991 ).

Experimental

Crystal data

BaCo₂(AsO₄)₂
M_r = 533.04
Hexagonal, $[R \overline 3]$
a = 5.007 (1) Å
c = 23.491 (5) Å
V = 510.02 (18) Å³
Z = 3
Mo Kα radiation
μ = 20.22 mm⁻¹
T = 293 (2) K
0.09 × 0.05 × 0.05 mm

Data collection

Nonius KappaCCD diffractometer
Absorption correction: multi-scan (Otwinowski & Minor, 1997 ; Otwinowski et al., 2003 ) T_min = 0.221, T_max = 0.362
681 measured reflections
341 independent reflections
336 reflections with I > 2σ(I)
R_int = 0.009

Refinement

R[F² > 2σ(F²)] = 0.014
wR(F²) = 0.038
S = 1.30
341 reflections
22 parameters
Δρ_max = 0.96 e Å⁻³
Δρ_min = −1.09 e Å⁻³

Table 1
Selected bond lengths (Å)

Ba1—O1	2.9344 (8)
Ba1—O2	3.1611 (17)
Co1—O2ⁱ	2.0791 (17)
Co1—O2	2.1017 (17)
As1—O1	1.656 (3)
As1—O2	1.7050 (17)
Symmetry code: (i) $[x-y+{\script{2\over 3}}, x+{\script{1\over 3}}, -z+{\script{1\over 3}}]$ .

Data collection: COLLECT (Nonius, 2002 ); cell refinement: SCALEPACK (Otwinowski & Minor, 1997); data reduction: DENZO-SMN (Otwinowski et al., 2003); method used to solve structure: starting parameters from an isostructural compound (Eymond et al., 1969a); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ) and WinGX (Farrugia, 1999 ); molecular graphics: ATOMS (Dowty, 2000 ); software used to prepare material for publication: publCIF (Westrip, 2008 ).

Supporting information

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536808025865/wm2189sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536808025865/wm2189Isup2.hkl

checkCIF report

Comment top

The crystal structures of phosphates, arsenates and vanadates with the general formula AM₂(XO₄)₂ where A = alkaline earth metal, M = Mg or divalent first row transition elements and X = P, As or V, are relatively well known (Bircsak & Harrison, 1998; El-Bali et al., 1993a,b, 1999; Eymond et al., 1969a,b; Hemon & Courbion, 1990; Kreidler & Hummel, 1961; Lucas et al., 1998; Moquine et al., 1993; Osterloh & Müller-Buschbaum, 1994; Wichmann & Müller-Buschbaum, 1984, and references therein). These phases adopt different structure types and exhibit interesting physical properties (phase transitions, magnetism). Six compounds, viz. BaMg₂(AsO₄)₂, BaCo₂(AsO₄)₂ (Eymond et al., 1969b), BaNi₂(AsO₄)₂ (Eymond et al., 1969a,b), BaCo₂(PO₄)₂ (Bircsak & Harrison, 1998), BaNi₂(PO₄)₂ (El-Bali et al., 1999; Faza et al., 2001) and BaNi₂(VO₄)₂ (Wichmann & Müller-Buschbaum, 1984; Rogado et al., 2002) are isostructural with the title compound, BaCo₂(AsO₄)₂. The underlying crystal structure was described for the first time for BaNi₂(AsO₄)₂ by Eymond et al. (1969a). Although two-dimensional magnetic properties of these compounds have been widely studied (Dojčilović et al., 1994; Regnault et al., 2006, and references therein), a full determination of their crystal structures was not given for all members of this structural family. Hydrothermal synthesis and the crystal structure of BaCo₂(AsO₄)₂ are presented in this communication.

Besides BaCoAs₂O₇ (Mihajlović et al., 2004), BaCo₂(AsO₄)₂ represents the second compound structurally characterised in the system BaO–CoO–As₂O₅. Its crystal structure is made up of brucite-like sheets of edge-sharing CoO₆ octahedra parallel to (001), with one-thirds of the octahedral positions being vacant. AsO₄ tetrahedra are situated above and below the sheets. The resulting anionic [Co₂(AsO₄)₂]^2- layers are stacked with a sequence ABCABC along [001] and are laterally displaced by Δx = 2/3a, with Δx = 1/3b between the layers. Adjacent layers are interconnected by BaO₁₂ polyhedra to form a three-dimensional framework (Fig. 1).

The Ba1 atom has site symmetry 3 and is coordinated by twelve oxygen atoms (Fig. 2) with an average Ba1—O bond length of 3.048 Å. This bond length compares well with the average bond length for Ba—O distances of 3.015 Å in the isostructural Ni compound BaNi₂(AsO₄)₂ (Eymond et al., 1969a,b). The Ba1 atom is bonded to six O1 and six O2 atoms, resulting in a distorted cuboctahedral coordination polyhedron. The Co1 atom has site-symmetry 3 and is octahedrally coordinated to O1 atoms with a mean Co1—O1 distance of 2.091 Å. The As1O₄ tetrahedron (3 symmetry) exhibits an average bond length of 1.692 Å, with two symmetrically independent As1—O bonds of 1.656 (3) Å (O1) and of 1.7050 (17) Å (O2, 3×) due to the different other coordination partners of the two oxygen atoms. O1, which bridges the barium ions, shows a shorter As1—O bond than O2, which bridges the cobalt ions (Fig. 2).

Bond-valence calculations for all atoms, using the parameters of Brese & O'Keeffe (1991), give 1.63 v.u. (valence units) for Ba1, 2.04 v.u. for Co1, 4.89 v.u. for As1, and 1.53 v.u and 1.96 v.u for O1 and O2, respectively. If one takes into account that the O2 atom is bonded to two Co1, one As1, and one Ba1 atom, and the O1 atom is bonded to one As1 and three Ba1 neighbours, the calculated values are close to the theoretical valences. However, it is worth mentioning that in BaCo₂(AsO₄)₂ and all isostructural compounds the Ba1 atom is strongly undersaturated in terms of its bond valence.

Related literature top

For isostructural compounds, see: Eymond et al. (1969a,b); Bircsak & Harrison (1998); El-Bali et al. (1999); Faza et al. (2001); Rogado et al. (2002); Wichmann, & Müller-Buschbaum (1984). For magnetic properties of BaCo₂(AsO₄)₂, see: Dojčilović et al. (1994); Regnault et al. (2006). For related compounds, see: Effenberger & Pertlik (1993); El-Bali et al. (1993a,b); Hemon & Courbion (1990); Kreidler & Hummel (1961); Lucas et al. (1998); Mihajlović et al. (2004); Moquine et al. (1993); Osterloh & Müller-Buschbaum (1994). For general background, see: Brese & O'Keeffe (1991).

Experimental top

Single crystals of BaCo₂(AsO₄)₂ were obtained as reaction products from mixtures of Ba(OH)₂.8H₂O (Merck, >97%), Co(OH)₂ (Alfa Products) and As₂O₅ (Alfa Products, >99.9%) under hydrothermal conditions. The mixture was transferred into a Teflon vessel and filled to approximately 70% of its inner volume with distilled water (pH of the resulting solution was ≈ 2.5). Finally, the vessel was enclosed into a stainless steel autoclave and was heated from room temperature to 493 K (2 h), held at 493 K for 24 h, then cooled to 393 K within 14 h, kept at this temperature for 24 h, and finally cooled to room temperature within 4 h. At the end of the reaction the pH was ≈ 6. The solid reaction products were filtered and washed thoroughly with distilled water. BaCo₂(AsO₄)₂ (yield ca 50%) crystallized as transparent pink crystals and was accompanied with prismatic blue–green crystals of BaCoAs₂O₇ (Mihajlović et al., 2004) (yield ca 30%) and Co₂As₂O₇(H₂O)₂ (Effenberger & Pertlik, 1993) (yield ca 15%), besides very few prismatic blue crystals of an yet unidentified compound (yield ca 5%). All crystals were up to 0.2 mm in length.

Computing details top

Data collection: COLLECT (Nonius, 2002); cell refinement: SCALEPACK (Otwinowski & Minor, 1997); data reduction: DENZO-SMN (Otwinowski et al., 2003); program(s) used to solve structure: starting parameters from an isostructural compound (Eymond et al., 1969a); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008) and WinGX (Farrugia, 1999); molecular graphics: ATOMS (Dowty, 2000); software used to prepare material for publication: publCIF (Westrip, 2008).

Figures top

	Fig. 1. The crystal structure of BaCo₂(AsO₄)₂ with sheets consisting of CoO₆ octahedra and AsO₄ tetrahedra (both in polyhedral representation) parallel to (001). Ba atoms are displayed as spheres.
	Fig. 2. Coordination of Ba and Co with atoms displayed as ellipsoids at the 50% probability level.

Barium dicobalt(II) bis-arsenate(V) top

Crystal data top

BaCo₂(AsO₄)₂	D_x = 5.206 Mg m⁻³
M_r = 533.04	Mo Kα radiation, λ = 0.71073 Å
Hexagonal, R3	Cell parameters from 675 reflections
Hall symbol: -R 3	θ = 1.0–30.0°
a = 5.007 (1) Å	µ = 20.22 mm⁻¹
c = 23.491 (5) Å	T = 293 K
V = 510.02 (18) Å³	Pseudo-hexagonal plate, pink
Z = 3	0.09 × 0.05 × 0.05 mm
F(000) = 720

Data collection top

Nonius KappaCCD diffractometer	341 independent reflections
Radiation source: fine-focus sealed tube	336 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.009
ϕ and ω scans	θ_max = 30.0°, θ_min = 2.6°
Absorption correction: multi-scan (Otwinowski & Minor, 1997; Otwinowski et al., 2003)	h = −7→7
T_min = 0.221, T_max = 0.362	k = −5→5
681 measured reflections	l = −33→33

Refinement top

Refinement on F²	Primary atom site location: isomorphous structure methods
Least-squares matrix: full	w = 1/[σ²(F_o²) + (0.0133P)² + 3.104P] where P = (F_o² + 2F_c²)/3
R[F² > 2σ(F²)] = 0.014	(Δ/σ)_max < 0.001
wR(F²) = 0.038	Δρ_max = 0.96 e Å⁻³
S = 1.30	Δρ_min = −1.09 e Å⁻³
341 reflections	Extinction correction: SHELXL97 (Sheldrick, 2008), Fc^*=kFc[1+0.001xFc²λ³/sin(2θ)]^-1/4
22 parameters	Extinction coefficient: 0.0118 (5)
0 restraints

Crystal data top

BaCo₂(AsO₄)₂	Z = 3
M_r = 533.04	Mo Kα radiation
Hexagonal, R3	µ = 20.22 mm⁻¹
a = 5.007 (1) Å	T = 293 K
c = 23.491 (5) Å	0.09 × 0.05 × 0.05 mm
V = 510.02 (18) Å³

Data collection top

Nonius KappaCCD diffractometer	341 independent reflections
Absorption correction: multi-scan (Otwinowski & Minor, 1997; Otwinowski et al., 2003)	336 reflections with I > 2σ(I)
T_min = 0.221, T_max = 0.362	R_int = 0.009
681 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.014	22 parameters
wR(F²) = 0.038	0 restraints
S = 1.30	Δρ_max = 0.96 e Å⁻³
341 reflections	Δρ_min = −1.09 e Å⁻³

Special details top

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Refinement. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > 2sigma(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
Ba1	0.0000	0.0000	0.0000	0.01170 (15)
Co1	0.0000	0.0000	0.17014 (2)	0.00614 (16)
As1	0.3333	0.6667	0.091941 (18)	0.00473 (15)
O1	0.3333	0.6667	0.02145 (13)	0.0118 (6)
O2	0.0163 (4)	0.3375 (4)	0.11476 (7)	0.0077 (3)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Ba1	0.01138 (17)	0.01138 (17)	0.0124 (2)	0.00569 (8)	0.000	0.000
Co1	0.00474 (19)	0.00474 (19)	0.0089 (3)	0.00237 (9)	0.000	0.000
As1	0.00414 (16)	0.00414 (16)	0.0059 (2)	0.00207 (8)	0.000	0.000
O1	0.0149 (9)	0.0149 (9)	0.0055 (13)	0.0075 (5)	0.000	0.000
O2	0.0055 (7)	0.0050 (7)	0.0116 (8)	0.0019 (6)	0.0017 (6)	0.0020 (6)

Geometric parameters (Å, º) top

Ba1—O1ⁱ	2.9344 (8)	Ba1—O2^ix	3.1611 (17)
Ba1—O1ⁱⁱ	2.9344 (8)	Co1—O2^x	2.0791 (17)
Ba1—O1ⁱⁱⁱ	2.9344 (8)	Co1—O2^xi	2.0791 (17)
Ba1—O1	2.9344 (8)	Co1—O2^xii	2.0792 (17)
Ba1—O1^iv	2.9344 (8)	Co1—O2^vii	2.1017 (17)
Ba1—O1^v	2.9344 (8)	Co1—O2	2.1017 (17)
Ba1—O2^vi	3.1611 (17)	Co1—O2^vi	2.1017 (17)
Ba1—O2	3.1611 (17)	As1—O1	1.656 (3)
Ba1—O2^vii	3.1611 (17)	As1—O2^xiii	1.7050 (17)
Ba1—O2ⁱⁱⁱ	3.1611 (17)	As1—O2	1.7050 (17)
Ba1—O2^viii	3.1611 (17)	As1—O2^xiv	1.7050 (17)

O1ⁱ—Ba1—O1ⁱⁱ	180.00 (12)	O2^vii—Ba1—O2ⁱⁱⁱ	126.22 (5)
O1ⁱ—Ba1—O1ⁱⁱⁱ	117.11 (3)	O1ⁱ—Ba1—O2^viii	52.94 (6)
O1ⁱⁱ—Ba1—O1ⁱⁱⁱ	62.89 (3)	O1ⁱⁱ—Ba1—O2^viii	127.06 (6)
O1ⁱ—Ba1—O1	62.89 (3)	O1ⁱⁱⁱ—Ba1—O2^viii	82.85 (6)
O1ⁱⁱ—Ba1—O1	117.11 (3)	O1—Ba1—O2^viii	97.15 (6)
O1ⁱⁱⁱ—Ba1—O1	180.00 (12)	O1^iv—Ba1—O2^viii	106.72 (6)
O1ⁱ—Ba1—O1^iv	117.11 (3)	O1^v—Ba1—O2^viii	73.28 (6)
O1ⁱⁱ—Ba1—O1^iv	62.89 (3)	O2^vi—Ba1—O2^viii	180.00 (7)
O1ⁱⁱⁱ—Ba1—O1^iv	117.11 (3)	O2—Ba1—O2^viii	126.22 (5)
O1—Ba1—O1^iv	62.89 (3)	O2^vii—Ba1—O2^viii	126.22 (5)
O1ⁱ—Ba1—O1^v	62.89 (3)	O2ⁱⁱⁱ—Ba1—O2^viii	53.78 (5)
O1ⁱⁱ—Ba1—O1^v	117.11 (3)	O1ⁱ—Ba1—O2^ix	82.85 (6)
O1ⁱⁱⁱ—Ba1—O1^v	62.89 (3)	O1ⁱⁱ—Ba1—O2^ix	97.15 (6)
O1—Ba1—O1^v	117.11 (3)	O1ⁱⁱⁱ—Ba1—O2^ix	106.72 (6)
O1^iv—Ba1—O1^v	180.00 (12)	O1—Ba1—O2^ix	73.28 (6)
O1ⁱ—Ba1—O2^vi	127.06 (6)	O1^iv—Ba1—O2^ix	52.94 (6)
O1ⁱⁱ—Ba1—O2^vi	52.94 (6)	O1^v—Ba1—O2^ix	127.06 (6)
O1ⁱⁱⁱ—Ba1—O2^vi	97.15 (6)	O2^vi—Ba1—O2^ix	126.22 (5)
O1—Ba1—O2^vi	82.85 (6)	O2—Ba1—O2^ix	126.22 (5)
O1^iv—Ba1—O2^vi	73.28 (6)	O2^vii—Ba1—O2^ix	180.00 (3)
O1^v—Ba1—O2^vi	106.72 (6)	O2ⁱⁱⁱ—Ba1—O2^ix	53.78 (5)
O1ⁱ—Ba1—O2	73.28 (6)	O2^viii—Ba1—O2^ix	53.78 (5)
O1ⁱⁱ—Ba1—O2	106.72 (6)	O2^x—Co1—O2^xi	92.91 (7)
O1ⁱⁱⁱ—Ba1—O2	127.06 (6)	O2^x—Co1—O2^xii	92.91 (7)
O1—Ba1—O2	52.94 (6)	O2^xi—Co1—O2^xii	92.91 (7)
O1^iv—Ba1—O2	97.15 (6)	O2^x—Co1—O2^vii	92.34 (6)
O1^v—Ba1—O2	82.85 (6)	O2^xi—Co1—O2^vii	174.36 (6)
O2^vi—Ba1—O2	53.78 (5)	O2^xii—Co1—O2^vii	88.86 (9)
O1ⁱ—Ba1—O2^vii	97.15 (6)	O2^x—Co1—O2	174.36 (6)
O1ⁱⁱ—Ba1—O2^vii	82.85 (6)	O2^xi—Co1—O2	88.86 (9)
O1ⁱⁱⁱ—Ba1—O2^vii	73.28 (6)	O2^xii—Co1—O2	92.34 (6)
O1—Ba1—O2^vii	106.72 (6)	O2^vii—Co1—O2	85.72 (7)
O1^iv—Ba1—O2^vii	127.06 (6)	O2^x—Co1—O2^vi	88.86 (9)
O1^v—Ba1—O2^vii	52.94 (6)	O2^xi—Co1—O2^vi	92.34 (6)
O2^vi—Ba1—O2^vii	53.78 (5)	O2^xii—Co1—O2^vi	174.36 (6)
O2—Ba1—O2^vii	53.78 (5)	O2^vii—Co1—O2^vi	85.72 (7)
O1ⁱ—Ba1—O2ⁱⁱⁱ	106.72 (6)	O2—Co1—O2^vi	85.72 (7)
O1ⁱⁱ—Ba1—O2ⁱⁱⁱ	73.28 (6)	O1—As1—O2^xiii	108.33 (6)
O1ⁱⁱⁱ—Ba1—O2ⁱⁱⁱ	52.94 (6)	O1—As1—O2	108.33 (6)
O1—Ba1—O2ⁱⁱⁱ	127.06 (6)	O2^xiii—As1—O2	110.59 (5)
O1^iv—Ba1—O2ⁱⁱⁱ	82.85 (6)	O1—As1—O2^xiv	108.33 (6)
O1^v—Ba1—O2ⁱⁱⁱ	97.15 (6)	O2^xiii—As1—O2^xiv	110.59 (5)
O2^vi—Ba1—O2ⁱⁱⁱ	126.22 (5)	O2—As1—O2^xiv	110.59 (5)
O2—Ba1—O2ⁱⁱⁱ	180.00 (7)

Symmetry codes: (i) −x, −y+1, −z; (ii) x, y−1, z; (iii) −x, −y, −z; (iv) −x+1, −y+1, −z; (v) x−1, y−1, z; (vi) −x+y, −x, z; (vii) −y, x−y, z; (viii) x−y, x, −z; (ix) y, −x+y, −z; (x) y−1/3, −x+y−2/3, −z+1/3; (xi) x−y+2/3, x+1/3, −z+1/3; (xii) −x−1/3, −y+1/3, −z+1/3; (xiii) −x+y, −x+1, z; (xiv) −y+1, x−y+1, z.

Experimental details

Crystal data
Chemical formula	BaCo₂(AsO₄)₂
M_r	533.04
Crystal system, space group	Hexagonal, R3
Temperature (K)	293
a, c (Å)	5.007 (1), 23.491 (5)
V (Å³)	510.02 (18)
Z	3
Radiation type	Mo Kα
µ (mm⁻¹)	20.22
Crystal size (mm)	0.09 × 0.05 × 0.05

Data collection
Diffractometer	Nonius KappaCCD diffractometer
Absorption correction	Multi-scan (Otwinowski & Minor, 1997; Otwinowski et al., 2003)
T_min, T_max	0.221, 0.362
No. of measured, independent and observed [I > 2σ(I)] reflections	681, 341, 336
R_int	0.009
(sin θ/λ)_max (Å⁻¹)	0.704

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.014, 0.038, 1.30
No. of reflections	341
No. of parameters	22
Δρ_max, Δρ_min (e Å⁻³)	0.96, −1.09

Computer programs: COLLECT (Nonius, 2002), SCALEPACK (Otwinowski & Minor, 1997), DENZO-SMN (Otwinowski et al., 2003), starting parameters from an isostructural compound (Eymond et al., 1969a), SHELXL97 (Sheldrick, 2008) and WinGX (Farrugia, 1999), ATOMS (Dowty, 2000), publCIF (Westrip, 2008).

Selected bond lengths (Å) top

Ba1—O1	2.9344 (8)	Co1—O2	2.1017 (17)
Ba1—O2	3.1611 (17)	As1—O1	1.656 (3)
Co1—O2ⁱ	2.0791 (17)	As1—O2	1.7050 (17)

Symmetry code: (i) x−y+2/3, x+1/3, −z+1/3.

Acknowledgements

The author gratefully acknowledges financial support by the Austrian Science Foundation (FWF) (grant No. T300-N19).

References

Bircsak, Z. & Harrison, W. T. A. (1998). Acta Cryst. C54, 1554–1556. Web of Science CrossRef CAS IUCr Journals Google Scholar
Brese, N. E. & O'Keeffe, M. (1991). Acta Cryst. B47, 192–197. CrossRef CAS Web of Science IUCr Journals Google Scholar
Dojčilović, J., Novaković, L., Napijalo, M. & Napijalo, M. (1994). Proc. Nat. Sci. Matica Srpska 85, 269–273. Google Scholar
Dowty, E. (2000). ATOMS for Windows. Shape Software, Kingsport, Tennessee, USA. Google Scholar
Effenberger, H. & Pertlik, F. (1993). Monatsch. Chem. 124, 381–389. CrossRef CAS Google Scholar
El-Bali, B., Bolte, M., Boukhari, A., Aride, J. & Taibe, M. (1999). Acta Cryst. C55, 701–702. Web of Science CSD CrossRef CAS IUCr Journals Google Scholar
El-Bali, B., Boukhari, A., Aride, J. & Abraham, F. (1993a). J. Solid State Chem. 104, 453–459. CrossRef CAS Web of Science Google Scholar
El-Bali, B., Boukhari, A., Holt, E. M. & Aride, J. (1993b). J. Crystallogr. Spectrosc. Res. 23, 1001–1004. CrossRef CAS Web of Science Google Scholar
Eymond, S., Martin, M. C. & Durif, A. (1969a). C. R. Acad. Sci. Ser. C, 286, 1694–1696. Google Scholar
Eymond, S., Martin, M. C. & Durif, A. (1969b). Mater. Res. Bull. 4, 595–600. CrossRef CAS Web of Science Google Scholar
Farrugia, L. J. (1999). J. Appl. Cryst. 32, 837–838. CrossRef CAS IUCr Journals Google Scholar
Faza, N., Treutmann, W. & Babel, D. (2001). Z. Anorg. Allg. Chem. 627, 687–692. Web of Science CrossRef CAS Google Scholar
Hemon, A. & Courbion, G. (1990). J. Solid State Chem. 85, 164–148. CrossRef CAS Web of Science Google Scholar
Kreidler, E. R. & Hummel, F. A. (1961). Inorg. Chem. 6, 524–528. CrossRef Web of Science Google Scholar
Lucas, F., Elfakir, A., Wallez, G. & Quarton, M. (1998). Can. Mineral. 36, 1045–1051. CAS Google Scholar
Mihajlović, T., Kolitsch, U. & Effenberger, H. (2004). J. Alloys Compd, 379, 103–109. Web of Science CrossRef Google Scholar
Moquine, A., Boukhari, A. & Darriet, J. (1993). J. Solid State Chem. 107, 362–367. Google Scholar
Nonius (2002). COLLECT. Nonius BV, Delft, The Netherlands. Google Scholar
Osterloh, D. & Müller-Buschbaum, Hk. (1994). Z. Anorg. Allg. Chem. 620, 651–654. CrossRef CAS Web of Science Google Scholar
Otwinowski, Z., Borek, D., Majewski, W. & Minor, W. (2003). Acta Cryst. A59, 228–234. Web of Science CrossRef CAS IUCr Journals Google Scholar
Otwinowski, Z. & Minor, W. (1997). Methods in Enzymology, Vol. 276, Macromolecular Crystallography, Part A, edited by C. W. Carter Jr & R. M. Sweet, pp. 307–326. New York: Academic Press. Google Scholar
Regnault, L. P., Boullier, C. & Henry, J. Y. (2006). Physica B, 385–386, 425–427. Web of Science CrossRef CAS Google Scholar
Rogado, N., Huang, Q., Lynn, J. W., Ramirez, A. P., Huse, D. & Cava, R. J. (2002). Phys. Rev. B, 65, 144443. Web of Science CrossRef Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
Westrip, S. P. (2008). publCIF. In preparation. Google Scholar
Wichmann, R. & Müller-Buschbaum, Hk. (1984). Rev. Chim. Miner. 21, 824–829. CAS Google Scholar