Synthesis and crystal structure of a new magnesium phosphate Na3RbMg7(PO4)6

Ben Hamed, T.; Boukhris, A.; Badri, A.; Ben Amara, M.

doi:10.1107/S2056989017006363

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ISSN: 2056-9890

Volume 73| Part 6| June 2017| Pages 817-820

https://doi.org/10.1107/S2056989017006363

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Synthesis and crystal structure of a new magnesium phosphate Na₃RbMg₇(PO₄)₆

Teycir Ben Hamed,^a ^* Amal Boukhris,^a Abdessalem Badri ^a and Mongi Ben Amara ^a

^aUnité de recherche, Matériaux Inorganiques, Faculté des Sciences, Université de Monastir, 5019, Monastir, Tunisia
^*Correspondence e-mail: teycirbenhamed@yahoo.fr

Edited by I. D. Brown, McMaster University, Canada (Received 15 March 2017; accepted 27 April 2017; online 5 May 2017)

A new magnesium phosphate, Na₃RbMg₇(PO₄)₆ [trisodium rubidium heptamagnesium hexakis(orthophosphate)], has been synthesized as single crystals by the flux method and exhibits a new structure type. Its original structure is built up from MgO_x (x = 5 and 6) polyhedra linked directly to each other through common corners or edges and reinforced by corner-sharing with PO₄ tetrahedra. The resulting anionic three-dimensional framework leads to the formation of channels along the [010] direction, in which the Na⁺ cations are located, while the Rb⁺ cations are located in large interstitial cavities.

Keywords: crystal structure; magnesium phosphate; anionic framework.

CCDC reference: 1546558

1. Chemical context

Magnesium phosphates are of increasing interest because of their potential applications as host materials for optically active rare earth ions (Seo, 2013 ; Kim et al., 2013 ; Boukhris et al., 2015 ). Moreover, these materials are very attractive in terms of basic research because they exhibit a rich structural chemistry due to their polymorphism (Ait Benhamou et al., 2010 ; Orlova et al., 2015 ).

Among the variety of magnesium monophosphates synthesized and characterized up to now, only four compounds belong to the system Na₃PO₄–Mg₃(PO₄)₂, namely NaMgPO₄, NaMg₄(PO₄)₃, Na₂Mg₅(PO₄)₄ and Na₄Mg(PO₄)₂ (Imura & Kawahara, 1997 ; Ben Amara et al., 1983 ; Yamakawa et al., 1994 ; Ghorbel et al., 1974 ). NaMgPO₄ compound crystallizes in the orthorhombic system with space group P2₁2₁2₁. Its structure involves MgO₆ and MgO₅ polyhedra linked by the monophosphate groups that form a three-dimensional framework. NaMg₄(PO₄)₃ is also orthorhombic, space group Pnma. Its structure is built up from three kinds of MgO₅ units sharing edges and corners and linked to each other by the PO₄ tetrahedra, leading to a three-dimensional framework. Na₂Mg₅(PO₄)₄, synthesized under pressure, crystallizes in the triclinic system. Its structure results from a three-dimensional framework of MgO₆ and MgO₅ polyhedra connected either directly via common corners or by means of the phosphate groups. Na₄Mg(PO₄)₂ exhibits two polymorphs, which were only identified by their powder diffraction patterns.

Starting from these compounds, suitable replacements of magnesium and/or sodium by large cations induces their transformation into several structural types for different Mg/P atomic ratios. NaMMg(PO₄)₂ (M = Ca, Sr and Ba) compounds are related to the glaserite-type structure (Alkemper & Fuess, 1998 ; Boukhris et al., 2012 , 2013 ). They adopt an anionic two-dimensional network with different symmetries as a function of the size of the M²⁺ cation. For an atomic ratio M:P of 7:6, magnesium phosphate compounds adopt a three-dimensional network related to the fillowite-type structure, as observed in Na₄Ca₄Mg₂₁(PO₄)₁₈, Na₂CaMg₇(PO₄)₆ and Na_2.5Y_0.5Mg₇(PO₄)₆ (Domanskii et al., 1982 ; McCoy et al., 1994 ; Jerbi et al., 2010a ). All of them crystallize with trigonal symmetry (space group R $[\overline{3}]$ ) and differ only by their cationic distributions. Three-dimensional anionic networks includes also original structures such as those observed in Na₁₈Ca₁₃Mg₅(PO₄)₁₈, NaCa₉Mg(PO₄)₇, Na₇LnMg₁₃(PO₄)₁₂ (Ln = La, Eu, Nd) (Yamakawa et al., 1994; Morozov et al., 1997 ; Jerbi et al., 2010b , 2012 ).

As a contribution to the investigation of the above-mentioned systems, we report here the structural characterization of a new magnesium phosphate Na₃RbMg₇(PO₄)₆, which is, to our knowledge, the first magnesium phosphate revealing an original structure for an atomic ratio Mg/P equal to 7/6.

2. Structural commentary

To the best of our knowledge, Na₃RbMg₇(PO₄)₆ exhibits a new structure type. A projection along the [010] direction of its structure (Fig. 1) clearly evidences the three-dimensional character of its anionic framework, which is built up from five different polyhedra MgO_x (x = 5, 6) and three kinds of PO₄ tetrahedra connected together by sharing edges and corners. The Na⁺ cations are located within channels running along the [010] direction while the Rb⁺ cations are found in the large interstitial cavities.

Figure 1
A view of the Na₃RbMg₇(PO₄)₆ structure along [010]. Colour key: MgO_x (x = 5 and 6; blue polyhedra), PO₄ (purple polyhedra), Rb (green spheres) and Na (yellow spheres).

A projection of the structure on the (012) plane (Fig. 2) shows that it can also be described on the basis of three kinds of rows (A, B and C) running parallel to the [100] direction. The first row (A; Fig. 3), consists of units with edge-sharing between one Na1O₈ and two Na2O₆ polyhedra. Such units alternate with Mg1O₅ polyhedra, leading to the sequence –Mg1–Na2–Na1–Na2–. The second row (B) consists of corner-sharing P2O₄, P3O₄, Mg4O₆ and Mg5O₅ polyhedra, forming the sequence –P3–Mg4–P2–Mg5–. Rows B and B′ are symmetrical with respect to the inversion centre located on the A row. The last row (C) includes units with corner-sharing between P1O₄ tetrahedra and Mg₂O₁₀ dimers, which consist of edge-sharing MgiO₆ (i = 2, 3) octahedra. These units alternate with RbO₁₂ polyhedra to form a –P1–[Mg2,Mg3]–P1–Rb– sequence. These rows, connected to each other through common corners or edges, occur with a sequence of ABCB′.

Figure 2
A view down the b axis, showing ABCB' rows made of PO₄ tetrahedra and Mg, Na and Rb atoms.

Figure 3
A view of parallel rows of ABC polyhedra.

There are five distinct Mg sites. The Mg1 atom is displaced slightly from the inversion center, statistically occupying two symmetry-related positions. As a consequence, the Mg1O₆ polyhedron exhibits two distances that are long [2.241 (5) Å] compared to the other Mg1—O distances, which vary from 1.969 (10) to 2.030 (10) Å. Thus, this environment can be considered as [4 + 1]. The average value of 2.005 (10) Å calculated from the four short distances is slightly higher but consistent with that of 1.930 (2) Å reported for the tetra-coordinated Mg²⁺ cation in KMgPO₄ (Wallez et al.,1998 ). Sites Mg2 and Mg3 are located on twofold rotation axes and have slightly distorted octahedral environments with Mg—O distances varying from 2.052 (3) to 2.202 (2) Å for Mg2 and from 2.042 (2) to 2.169 (2) Å for Mg3. The corresponding average values of 2.123 and 2.103 Å, respectively, are in a good agreement with that of 2.14 Å observed for hexa-coordinated Mg²⁺ ions in Mg₃(PO₄)₂ (Jaulmes et al., 1997 ). Site Mg4 is [5 + 1]-coordinated, with five short distances varying from 1.981 (3) to 2.050 (3) Å and a sixth longer distance of 2.5734 (3) Å. A similar environment has already been observed in Mg₃(PO₄)₂ (Jaulmes et al., 1997). Site Mg5 is five-coordinated with Mg—O distances ranging from 2.020 (3) to 2.148 (3) Å. The corresponding mean distance of 2.07 Å is close to that of 2.08 Å observed for Mg²⁺ with the same coordination in NaMg₄(PO₄)₃ (Ben Amara et al., 1983). The P—O distances within the PO₄ tetrahedra are in the range of 1.518 (2)–1.552 (2) Å with an overall mean value of 1.539 Å, very close to that of 1.537 Å predicted by Baur (1974 ) for monophosphate groups.

The environments of the alkali cations are shown in Fig. 4. Those of the two crystallographic distinct Na sites were determined assuming a maximum sodium–oxygen distance L_max of 3.13 Å, as suggested by Donnay & Allmann (1970 ). As in the case of the Mg1 atom, the sodium atom Na1 is also moved slightly away from the inversion center and statistically occupying two symmetry-related positions. This moving probably occurs to accommodate the environment of the Na1 site, which then consists of eight oxygen atoms with Na—O distances varying from 2.303 (7) to 2.963 (6) Å. Na2 is bound to only six oxygen atoms, with Na2—O distances in the range 2.246 (3)–2.962 (3) Å. The Rb⁺ ion is located on a twofold rotation axis and occupies a single site whose environment was determined assuming all Rb—O distances to be shorter than the shortest distance between Rb⁺ and its nearest cation. This environment then consists of twelve oxygen atoms with Rb—O distances ranging from 2.923 (3) to 3.517 (2) Å.

Figure 4
The environment of the (a) Na1⁺, (b) Na2⁺ and (c) Rb⁺ cations, showing displacement ellipsoids drawn at the 50% probability level.

3. Synthesis and crystallization

Single crystals of Na₃RbMg₇(PO₄)₆ were grown in a flux of sodium molybdate, Na₂MoO₄, with a P:Mo atomic ratio of 2:1. Appropriate amounts of the starting reactants (NH₄)H₂PO₄, Na₂CO₃, Rb₂CO₃, (MgCO₃)₄Mg(OH)₂·5H₂O and Na₂MoO₄·2H₂O were dissolved in nitric acid and the obtained solution was evaporated to dryness. The residue was homogenized by grinding in an agate mortar, and subsequently heated in a platinum crucible for 24 h at 673 K and then for 12 h at 873 K. After being reground, the sample was melted for 2 h at 1273 K and then cooled slowly down to room temperature at a rate of 10 K h⁻¹. The solidified melt was washed with boiling water to dissolve the flux. Colourless, irregularly shaped crystals were extracted from the final product.

4. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 1. The refinement was performed on the basis of electric neutrality and similar works. The atomic positions are determined by comparison with the refinements reported by Jerbi et al. (2010a) and McCoy et al. (1994).

Table 1
Experimental details

Crystal data
Chemical formula	Na₃RbMg₇(PO₄)₆
M_r	894.43
Crystal system, space group	Monoclinic, C2/c
Temperature (K)	293
a, b, c (Å)	12.734 (3), 10.685 (3), 15.498 (5)
β (°)	112.83 (2)
V (Å³)	1943.5 (10)
Z	4
Radiation type	Mo Kα
μ (mm⁻¹)	3.47
Crystal size (mm)	0.16 × 0.10 × 0.07

Data collection
Diffractometer	Enraf–Nonius Turbo CAD-4
Absorption correction	Part of the refinement model (ΔF) (Parkin et al., 1995 )
T_min, T_max	0.377, 0.485
No. of measured, independent and observed [I > 2σ(I)] reflections	2333, 2333, 1968
R_int	0.020
(sin θ/λ)_max (Å⁻¹)	0.660

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.036, 0.100, 1.07
No. of reflections	2333
No. of parameters	196
Δρ_max, Δρ_min (e Å⁻³)	0.87, −1.49
Computer programs: CAD-4 EXPRESS (Enraf–Nonius, 1994 ), XCAD4 (Harms & Wocadlo, 1995 ), SIR92 (Altomare et al., 1993 ), SHELXL2014 (Sheldrick, 2015 ), DIAMOND (Brandenburg et al., 1999 ) and WinGX (Farrugia, 2012 ).

Supporting information

CCDC reference: 1546558

Crystal structure: contains datablocks global, I. DOI: https://doi.org/10.1107/S2056989017006363/br2264sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989017006363/br2264Isup2.hkl

checkCIF report

Computing details top

Data collection: CAD-4 EXPRESS (Enraf–Nonius, 1994); cell refinement: CAD-4 EXPRESS (Enraf–Nonius, 1994); data reduction: XCAD4 (Harms & Wocadlo, 1995); program(s) used to solve structure: SIR92 (Altomare et al., 1993); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015); molecular graphics: DIAMOND (Brandenburg et al., 1999); software used to prepare material for publication: WinGX (Farrugia, 2012).

Trisodium rubidium heptamagnesium hexakis(orthophosphate) top

Crystal data top

Mg₇Na₃O₂₄P₆Rb	F(000) = 1744
M_r = 894.43	D_x = 3.057 Mg m⁻³
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
a = 12.734 (3) Å	Cell parameters from 25 reflections
b = 10.685 (3) Å	θ = 7.5–10.8°
c = 15.498 (5) Å	µ = 3.47 mm⁻¹
β = 112.83 (2)°	T = 293 K
V = 1943.5 (10) Å³	Prism, colourless
Z = 4	0.16 × 0.10 × 0.07 mm

Data collection top

Enraf–Nonius Turbo CAD-4 diffractometer	R_int = 0.020
non–profiled ω/2τ scans	θ_max = 28.0°, θ_min = 2.6°
Absorption correction: part of the refinement model (ΔF) (Parkin et al., 1995)	h = −16→15
T_min = 0.377, T_max = 0.485	k = 0→14
2333 measured reflections	l = 0→20
2333 independent reflections	2 standard reflections every 60 min
1968 reflections with I > 2σ(I)	intensity decay: −2%

Refinement top

Refinement on F²	196 parameters
Least-squares matrix: full	0 restraints
R[F² > 2σ(F²)] = 0.036	w = 1/[σ²(F_o²) + (0.0549P)² + 7.6361P] where P = (F_o² + 2F_c²)/3
wR(F²) = 0.100	(Δ/σ)_max < 0.001
S = 1.07	Δρ_max = 0.87 e Å⁻³
2333 reflections	Δρ_min = −1.49 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.

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

	x	y	z	U_iso*/U_eq	Occ. (<1)
Rb	0.5000	0.74607 (5)	0.7500	0.02406 (16)
Na1	0.2552 (5)	0.7550 (6)	0.0226 (3)	0.0279 (12)	0.5
Na2	−0.01858 (14)	0.76242 (14)	0.98277 (13)	0.0226 (4)
Mg1	0.2487 (8)	0.2471 (9)	0.0142 (4)	0.0098 (10)	0.5
Mg2	0.0000	0.58859 (15)	0.7500	0.0071 (3)
Mg3	0.5000	0.62142 (14)	0.2500	0.0059 (3)
Mg4	0.18422 (9)	0.54259 (10)	0.12717 (7)	0.0065 (2)
Mg5	0.19042 (9)	0.99696 (11)	0.14183 (7)	0.0081 (2)
P1	0.28980 (7)	0.76938 (7)	0.27439 (6)	0.00668 (18)
O11	0.41297 (19)	0.7658 (2)	0.27801 (17)	0.0097 (5)
O12	0.25429 (18)	0.9074 (2)	0.27435 (15)	0.0084 (4)
O13	0.2043 (2)	0.7106 (3)	0.18543 (18)	0.0164 (5)
O14	0.2884 (2)	0.6963 (2)	0.36018 (17)	0.0146 (5)
P2	0.41165 (6)	0.50005 (7)	0.08098 (5)	0.00531 (18)
O21	0.53692 (18)	0.5150 (2)	0.15135 (15)	0.0084 (4)
O22	0.38853 (19)	0.5698 (2)	0.98959 (16)	0.0113 (5)
O23	0.34627 (19)	0.5654 (2)	0.13363 (15)	0.0085 (4)
O24	0.38345 (19)	0.3619 (2)	0.06370 (17)	0.0119 (5)
P3	0.09357 (6)	0.50198 (7)	0.92791 (5)	0.00484 (18)
O31	−0.03126 (18)	0.4851 (2)	0.86059 (16)	0.0100 (5)
O32	0.10990 (18)	0.6126 (2)	0.99444 (15)	0.0103 (5)
O33	0.15211 (18)	0.5301 (2)	0.85956 (16)	0.0109 (5)
O34	0.1418 (2)	0.3884 (2)	0.99025 (18)	0.0136 (5)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Rb	0.0278 (3)	0.0250 (3)	0.0200 (3)	0.000	0.0099 (2)	0.000
Na1	0.0132 (16)	0.0218 (17)	0.050 (4)	−0.0034 (12)	0.014 (3)	0.009 (3)
Na2	0.0180 (8)	0.0166 (7)	0.0412 (10)	−0.0006 (6)	0.0202 (7)	−0.0027 (6)
Mg1	0.0043 (9)	0.0081 (11)	0.015 (3)	0.0002 (8)	0.001 (2)	−0.001 (3)
Mg2	0.0052 (7)	0.0109 (7)	0.0054 (7)	0.000	0.0021 (5)	0.000
Mg3	0.0044 (7)	0.0099 (7)	0.0050 (6)	0.000	0.0037 (5)	0.000
Mg4	0.0035 (5)	0.0114 (5)	0.0052 (5)	−0.0010 (4)	0.0024 (4)	0.0014 (4)
Mg5	0.0036 (5)	0.0166 (6)	0.0055 (5)	0.0009 (4)	0.0033 (4)	−0.0002 (4)
P1	0.0030 (3)	0.0093 (4)	0.0098 (4)	−0.0003 (3)	0.0046 (3)	−0.0010 (3)
O11	0.0045 (10)	0.0115 (11)	0.0158 (11)	0.0007 (8)	0.0070 (9)	0.0000 (9)
O12	0.0059 (10)	0.0106 (11)	0.0097 (11)	0.0019 (8)	0.0042 (9)	−0.0004 (8)
O13	0.0076 (11)	0.0216 (13)	0.0179 (12)	−0.0027 (10)	0.0026 (9)	−0.0117 (11)
O14	0.0149 (12)	0.0142 (12)	0.0203 (13)	0.0005 (10)	0.0129 (10)	0.0051 (10)
P2	0.0029 (4)	0.0105 (4)	0.0038 (4)	−0.0006 (3)	0.0028 (3)	−0.0011 (3)
O21	0.0027 (10)	0.0169 (11)	0.0056 (10)	−0.0002 (8)	0.0017 (8)	−0.0028 (8)
O22	0.0098 (11)	0.0191 (12)	0.0060 (10)	−0.0007 (9)	0.0043 (9)	0.0011 (9)
O23	0.0065 (10)	0.0139 (11)	0.0072 (10)	0.0000 (8)	0.0049 (8)	−0.0026 (9)
O24	0.0081 (11)	0.0112 (11)	0.0165 (12)	−0.0023 (9)	0.0049 (9)	−0.0042 (9)
P3	0.0025 (4)	0.0090 (4)	0.0040 (4)	0.0005 (3)	0.0024 (3)	0.0008 (3)
O31	0.0027 (10)	0.0181 (12)	0.0089 (11)	−0.0016 (9)	0.0018 (8)	−0.0003 (9)
O32	0.0091 (11)	0.0144 (11)	0.0082 (11)	0.0003 (9)	0.0041 (9)	−0.0034 (9)
O33	0.0044 (10)	0.0232 (12)	0.0066 (10)	0.0001 (9)	0.0037 (8)	0.0014 (9)
O34	0.0093 (11)	0.0141 (11)	0.0197 (12)	0.0061 (9)	0.0080 (9)	0.0088 (10)

Geometric parameters (Å, º) top

Rb—O24ⁱ	2.923 (3)	Mg2—O33^xvi	2.115 (2)
Rb—O24ⁱⁱ	2.923 (3)	Mg2—O33	2.115 (2)
Rb—O13ⁱⁱⁱ	3.163 (3)	Mg2—O31	2.202 (2)
Rb—O13^iv	3.163 (3)	Mg2—O31^xvi	2.202 (2)
Rb—O31^v	3.186 (2)	Mg3—O11	2.042 (2)
Rb—O31^vi	3.186 (2)	Mg3—O11^xvii	2.042 (2)
Rb—O21ⁱ	3.301 (2)	Mg3—O21	2.100 (2)
Rb—O21ⁱⁱ	3.301 (2)	Mg3—O21^xvii	2.100 (2)
Rb—O14ⁱⁱⁱ	3.452 (3)	Mg3—O23^xvii	2.169 (2)
Rb—O14^iv	3.452 (3)	Mg3—O23	2.169 (2)
Rb—O12^iv	3.517 (2)	Mg4—O13	1.981 (3)
Rb—O12ⁱⁱⁱ	3.517 (2)	Mg4—O12^xv	2.026 (3)
Na1—O32^vii	2.303 (7)	Mg4—O23	2.041 (2)
Na1—O32^iv	2.318 (7)	Mg4—O32^vii	2.043 (3)
Na1—O22^iv	2.573 (7)	Mg4—O31^xviii	2.050 (2)
Na1—O23	2.620 (7)	Mg4—O34^vii	2.573 (3)
Na1—O22^vii	2.782 (7)	Mg5—O22^iv	2.020 (3)
Na1—O13	2.878 (5)	Mg5—O21^xix	2.026 (2)
Na1—O33^iv	2.886 (6)	Mg5—O33^iv	2.034 (2)
Na1—O23^viii	2.963 (6)	Mg5—O12	2.121 (3)
Na2—O32	2.246 (3)	Mg5—O14^xx	2.148 (3)
Na2—O24^ix	2.340 (3)	P1—O13	1.521 (3)
Na2—O22^x	2.365 (3)	P1—O12	1.542 (2)
Na2—O34^xi	2.396 (3)	P1—O11	1.548 (2)
Na2—O14^xii	2.495 (3)	P1—O14	1.548 (2)
Na2—O11^xii	2.962 (3)	P2—O24	1.518 (2)
Mg1—O34^vii	1.969 (10)	P2—O22^vii	1.524 (2)
Mg1—O24	2.004 (10)	P2—O23	1.541 (2)
Mg1—O24^xiii	2.017 (10)	P2—O21	1.552 (2)
Mg1—O34^xiv	2.030 (10)	P3—O34	1.524 (2)
Mg1—O14^xv	2.241 (4)	P3—O32	1.528 (2)
Mg2—O11^iv	2.052 (3)	P3—O31	1.537 (2)
Mg2—O11^xii	2.052 (3)	P3—O33	1.543 (2)

O24ⁱ—Rb—O24ⁱⁱ	133.51 (9)	O24^ix—Na2—O22^x	92.29 (10)
O24ⁱ—Rb—O13ⁱⁱⁱ	84.83 (7)	O32—Na2—O34^xi	90.71 (10)
O24ⁱⁱ—Rb—O13ⁱⁱⁱ	101.86 (7)	O24^ix—Na2—O34^xi	71.97 (10)
O24ⁱ—Rb—O13^iv	101.86 (7)	O22^x—Na2—O34^xi	159.77 (12)
O24ⁱⁱ—Rb—O13^iv	84.83 (7)	O32—Na2—O14^xii	131.25 (11)
O13ⁱⁱⁱ—Rb—O13^iv	163.19 (10)	O24^ix—Na2—O14^xii	75.82 (9)
O24ⁱ—Rb—O31^v	136.57 (6)	O22^x—Na2—O14^xii	114.69 (10)
O24ⁱⁱ—Rb—O31^v	84.63 (6)	O34^xi—Na2—O14^xii	74.54 (9)
O13ⁱⁱⁱ—Rb—O31^v	110.05 (7)	O32—Na2—O11^xii	85.19 (9)
O13^iv—Rb—O31^v	54.74 (6)	O24^ix—Na2—O11^xii	128.61 (10)
O24ⁱ—Rb—O31^vi	84.63 (6)	O22^x—Na2—O11^xii	99.52 (9)
O24ⁱⁱ—Rb—O31^vi	136.57 (6)	O34^xi—Na2—O11^xii	100.27 (10)
O13ⁱⁱⁱ—Rb—O31^vi	54.74 (6)	O14^xii—Na2—O11^xii	53.75 (8)
O13^iv—Rb—O31^vi	110.05 (7)	O34^vii—Mg1—O24	91.7 (4)
O31^v—Rb—O31^vi	73.42 (9)	O34^vii—Mg1—O24^xiii	88.6 (4)
O24ⁱ—Rb—O21ⁱ	47.00 (6)	O24—Mg1—O24^xiii	166.9 (2)
O24ⁱⁱ—Rb—O21ⁱ	90.86 (6)	O34^vii—Mg1—O34^xiv	167.0 (2)
O13ⁱⁱⁱ—Rb—O21ⁱ	72.22 (6)	O24—Mg1—O34^xiv	87.2 (4)
O13^iv—Rb—O21ⁱ	123.54 (6)	O24^xiii—Mg1—O34^xiv	89.6 (4)
O31^v—Rb—O21ⁱ	175.28 (6)	O34^vii—Mg1—O14^xv	89.2 (3)
O31^vi—Rb—O21ⁱ	110.99 (6)	O24—Mg1—O14^xv	104.7 (3)
O24ⁱ—Rb—O21ⁱⁱ	90.86 (6)	O24^xiii—Mg1—O14^xv	88.4 (3)
O24ⁱⁱ—Rb—O21ⁱⁱ	47.00 (6)	O34^xiv—Mg1—O14^xv	103.6 (3)
O13ⁱⁱⁱ—Rb—O21ⁱⁱ	123.54 (6)	O11^iv—Mg2—O11^xii	81.37 (14)
O13^iv—Rb—O21ⁱⁱ	72.22 (7)	O11^iv—Mg2—O33^xvi	117.11 (10)
O31^v—Rb—O21ⁱⁱ	110.99 (6)	O11^xii—Mg2—O33^xvi	89.56 (10)
O31^vi—Rb—O21ⁱⁱ	175.28 (6)	O11^iv—Mg2—O33	89.56 (10)
O21ⁱ—Rb—O21ⁱⁱ	64.66 (8)	O11^xii—Mg2—O33	117.11 (10)
O24ⁱ—Rb—O14ⁱⁱⁱ	126.45 (6)	O33^xvi—Mg2—O33	145.64 (16)
O24ⁱⁱ—Rb—O14ⁱⁱⁱ	63.05 (6)	O11^iv—Mg2—O31	145.19 (10)
O13ⁱⁱⁱ—Rb—O14ⁱⁱⁱ	44.16 (6)	O11^xii—Mg2—O31	86.60 (9)
O13^iv—Rb—O14ⁱⁱⁱ	131.70 (6)	O33^xvi—Mg2—O31	95.21 (10)
O31^v—Rb—O14ⁱⁱⁱ	85.51 (6)	O33—Mg2—O31	67.21 (9)
O31^vi—Rb—O14ⁱⁱⁱ	78.00 (6)	O11^iv—Mg2—O31^xvi	86.60 (9)
O21ⁱ—Rb—O14ⁱⁱⁱ	93.70 (6)	O11^xii—Mg2—O31^xvi	145.19 (10)
O21ⁱⁱ—Rb—O14ⁱⁱⁱ	103.71 (6)	O33^xvi—Mg2—O31^xvi	67.21 (9)
O24ⁱ—Rb—O14^iv	63.05 (6)	O33—Mg2—O31^xvi	95.20 (9)
O24ⁱⁱ—Rb—O14^iv	126.45 (6)	O31—Mg2—O31^xvi	119.70 (14)
O13ⁱⁱⁱ—Rb—O14^iv	131.70 (6)	O11—Mg3—O11^xvii	81.88 (14)
O13^iv—Rb—O14^iv	44.16 (6)	O11—Mg3—O21	149.00 (10)
O31^v—Rb—O14^iv	78.00 (6)	O11^xvii—Mg3—O21	87.76 (9)
O31^vi—Rb—O14^iv	85.51 (6)	O11—Mg3—O21^xvii	87.76 (9)
O21ⁱ—Rb—O14^iv	103.71 (6)	O11^xvii—Mg3—O21^xvii	149.00 (10)
O21ⁱⁱ—Rb—O14^iv	93.70 (6)	O21—Mg3—O21^xvii	114.43 (14)
O14ⁱⁱⁱ—Rb—O14^iv	159.44 (9)	O11—Mg3—O23^xvii	114.89 (10)
O24ⁱ—Rb—O12^iv	67.45 (6)	O11^xvii—Mg3—O23^xvii	89.77 (9)
O24ⁱⁱ—Rb—O12^iv	90.89 (6)	O21—Mg3—O23^xvii	94.09 (9)
O13ⁱⁱⁱ—Rb—O12^iv	150.50 (6)	O21^xvii—Mg3—O23^xvii	68.28 (9)
O13^iv—Rb—O12^iv	42.77 (6)	O11—Mg3—O23	89.77 (9)
O31^v—Rb—O12^iv	97.43 (6)	O11^xvii—Mg3—O23	114.89 (10)
O31^vi—Rb—O12^iv	128.18 (6)	O21—Mg3—O23	68.28 (9)
O21ⁱ—Rb—O12^iv	81.20 (5)	O21^xvii—Mg3—O23	94.09 (9)
O21ⁱⁱ—Rb—O12^iv	50.59 (5)	O23^xvii—Mg3—O23	147.97 (14)
O14ⁱⁱⁱ—Rb—O12^iv	153.49 (6)	O13—Mg4—O12^xv	111.06 (11)
O14^iv—Rb—O12^iv	43.24 (6)	O13—Mg4—O23	85.41 (10)
O24ⁱ—Rb—O12ⁱⁱⁱ	90.89 (6)	O12^xv—Mg4—O23	87.74 (10)
O24ⁱⁱ—Rb—O12ⁱⁱⁱ	67.45 (6)	O13—Mg4—O32^vii	93.13 (12)
O13ⁱⁱⁱ—Rb—O12ⁱⁱⁱ	42.77 (6)	O12^xv—Mg4—O32^vii	155.80 (11)
O13^iv—Rb—O12ⁱⁱⁱ	150.50 (6)	O23—Mg4—O32^vii	94.02 (10)
O31^v—Rb—O12ⁱⁱⁱ	128.18 (6)	O13—Mg4—O31^xviii	92.75 (11)
O31^vi—Rb—O12ⁱⁱⁱ	97.43 (6)	O12^xv—Mg4—O31^xviii	86.03 (10)
O21ⁱ—Rb—O12ⁱⁱⁱ	50.59 (5)	O23—Mg4—O31^xviii	172.38 (11)
O21ⁱⁱ—Rb—O12ⁱⁱⁱ	81.20 (5)	O32^vii—Mg4—O31^xviii	93.46 (10)
O14ⁱⁱⁱ—Rb—O12ⁱⁱⁱ	43.24 (6)	O13—Mg4—O34^vii	154.80 (11)
O14^iv—Rb—O12ⁱⁱⁱ	153.49 (6)	O12^xv—Mg4—O34^vii	93.48 (10)
O12^iv—Rb—O12ⁱⁱⁱ	124.43 (8)	O23—Mg4—O34^vii	90.10 (9)
O32^vii—Na1—O32^iv	163.38 (18)	O32^vii—Mg4—O34^vii	62.42 (9)
O32^vii—Na1—O22^iv	88.3 (2)	O31^xviii—Mg4—O34^vii	94.64 (9)
O32^iv—Na1—O22^iv	94.9 (3)	O22^iv—Mg5—O21^xix	89.44 (10)
O32^vii—Na1—O23	74.4 (2)	O22^iv—Mg5—O33^iv	92.64 (10)
O32^iv—Na1—O23	112.8 (3)	O21^xix—Mg5—O33^iv	175.75 (11)
O22^iv—Na1—O23	137.03 (19)	O22^iv—Mg5—O12	132.14 (11)
O32^vii—Na1—O22^vii	89.9 (2)	O21^xix—Mg5—O12	89.48 (10)
O32^iv—Na1—O22^vii	83.2 (2)	O33^iv—Mg5—O12	86.38 (10)
O22^iv—Na1—O22^vii	166.37 (17)	O22^iv—Mg5—O14^xx	110.57 (11)
O23—Na1—O22^vii	54.84 (15)	O21^xix—Mg5—O14^xx	92.12 (10)
Na1^viii—Na1—O13	150.6 (12)	O33^iv—Mg5—O14^xx	90.63 (10)
O32^vii—Na1—O13	67.64 (15)	O12—Mg5—O14^xx	117.28 (10)
O32^iv—Na1—O13	129.0 (2)	O13—P1—O12	106.71 (14)
O22^iv—Na1—O13	77.79 (16)	O13—P1—O11	112.40 (14)
O23—Na1—O13	59.29 (12)	O12—P1—O11	108.47 (12)
O22^vii—Na1—O13	113.9 (2)	O13—P1—O14	109.11 (15)
O32^vii—Na1—O33^iv	138.3 (2)	O12—P1—O14	112.44 (13)
O32^iv—Na1—O33^iv	56.44 (15)	O11—P1—O14	107.79 (13)
O22^iv—Na1—O33^iv	64.67 (16)	O24—P2—O22^vii	111.34 (14)
O23—Na1—O33^iv	103.37 (17)	O24—P2—O23	113.25 (13)
O22^vii—Na1—O33^iv	123.6 (2)	O22^vii—P2—O23	108.74 (13)
O13—Na1—O33^iv	75.63 (12)	O24—P2—O21	109.41 (13)
O32^vii—Na1—O23^viii	102.1 (2)	O22^vii—P2—O21	112.20 (13)
O32^iv—Na1—O23^viii	67.63 (16)	O23—P2—O21	101.56 (12)
O22^iv—Na1—O23^viii	52.91 (14)	O34—P3—O32	105.79 (14)
O23—Na1—O23^viii	168.2 (2)	O34—P3—O31	113.15 (14)
O22^vii—Na1—O23^viii	114.48 (15)	O32—P3—O31	112.52 (13)
O13—Na1—O23^viii	130.4 (2)	O34—P3—O33	114.02 (13)
O33^iv—Na1—O23^viii	86.8 (2)	O32—P3—O33	109.69 (14)
O32—Na2—O24^ix	143.52 (12)	O31—P3—O33	101.82 (13)
O32—Na2—O22^x	95.11 (10)

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

References

Ait Benhamou, R., Wallez, G., Loiseau, P., Viana, B., Elaatmani, M., Daoud, M. & Zegzouti, A. (2010). J. Solid State Chem. 183, 2082–2086. Web of Science CrossRef CAS Google Scholar
Alkemper, J. & Fuess, H. (1998). Z. Kristallogr. 213, 282–287. Web of Science CrossRef CAS Google Scholar
Altomare, A., Cascarano, G., Giacovazzo, C. & Guagliardi, A. (1993). J. Appl. Cryst. 26, 343–350. CrossRef Web of Science IUCr Journals Google Scholar
Baur, W. H. (1974). Acta Cryst. B30, 1195–1215. CrossRef CAS IUCr Journals Web of Science Google Scholar
Ben Amara, M., Vlasse, M., Olazcuaga, R., Le Flem, G. & Hagenmuller, P. (1983). Acta Cryst. C39, 936–939. CrossRef CAS Web of Science IUCr Journals Google Scholar
Boukhris, A., Glorieux, B. & Ben Amara, M. (2015). J. Mol. Struct. 1083, 319–329. Web of Science CrossRef CAS Google Scholar
Boukhris, A., Hidouri, M., Glorieux, B. & Ben Amara, M. (2013). J. Rare Earths, 31, 849–856. Web of Science CrossRef CAS Google Scholar
Boukhris, A., Hidouri, M., Glorieux, B. & Ben Amara, M. (2012). Mater. Chem. Phys. 137, 26–33. Web of Science CrossRef CAS Google Scholar
Brandenburg, K. (1999). DIAMOND. University of Bonn, Germany. Google Scholar
Domanskii, A. I., Smolin, Yu. I., Shepelev, Yu. F. & Majling, J. (1982). Sov. Phys. Crystallogr. 27, 535–537. Google Scholar
Donnay, G. & Allmann, R. (1970). Am. Mineral. 55, 1003–1015. CAS Google Scholar
Enraf–Nonius (1994). CAD-4 EXPRESS. Enraf–Nonius, Delft, The Net. Google Scholar
Farrugia, L. J. (2012). J. Appl. Cryst. 45, 849–854. Web of Science CrossRef CAS IUCr Journals Google Scholar
Ghorbel, A., d'Yvoire, F. & Dorrmieux-Morin, C. (1974). Bull. Soc. Chim. Fr. pp. 1239–1242. Google Scholar
Harms, K. & Wocadlo, S. (1995). XCAD4. University of Marburg, Germany. Google Scholar
Imura, H. & Kawahara, A. (1997). Acta Cryst. C53, 1733–1735. Web of Science CrossRef CAS IUCr Journals Google Scholar
Jaulmes, S., Elfakir, A., Quarton, M., Brunet, F. & Chopin, C. (1997). J. Solid State Chem. 129, 341–345. CrossRef CAS Web of Science Google Scholar
Jerbi, H., Hidouri, M. & Ben Amara, M. (2010a). J. Rare Earths, 28, 481–487. Web of Science CrossRef CAS Google Scholar
Jerbi, H., Hidouri, M., Glorieux, B., Darriet, J., Garcia, A., Jubera, V. & Ben Amara, M. (2010b). J. Solid State Chem. 183, 1752–1760. Web of Science CrossRef CAS Google Scholar
Jerbi, H., Hidouri, M. & Ben Amara, M. (2012). Acta Cryst. E68, i44. CrossRef IUCr Journals Google Scholar
Kim, S. W., Hasegawa, T., Ishigaki, T. K., Uematsu, K., Toda, K. & Sato, M. (2013). ECS Solid State Letters, 2, R49–R51. Google Scholar
McCoy, T. J., Steele, I. M., Keil, K., Leonard, B. F. & Endress, M. (1994). Am. Mineral. 79, 375–380. CAS Google Scholar
Morozov, V. A., Presnyakov, I. A., Belik, A. A., Khasanov, S. S. & Lazoryak, B. I. (1997). Kristallografiya, 42, 825–836. CAS Google Scholar
Orlova, M., Khainakov, S., Michailov, D., Perfler, L., Langes, Ch., Kahlenberg, V. & Orlova, A. (2015). J. Solid State Chem. 221, 224–229. Web of Science CSD CrossRef CAS Google Scholar
Parkin, S., Moezzi, B. & Hope, H. (1995). J. Appl. Cryst. 28, 53–56. CrossRef CAS Web of Science IUCr Journals Google Scholar
Seo, H. J. (2013). J. Ceram. Process. Res. 14(1), 22–25. Google Scholar
Sheldrick, G. M. (2015). Acta Cryst. C71, 3–8. Web of Science CrossRef IUCr Journals Google Scholar
Wallez, G., Colbeau-Justin, C., Le Mercier, T., Quarton, M. & Robert, F. (1998). J. Solid State Chem. 136, 175–180. Web of Science CrossRef CAS Google Scholar
Yamakawa, J., Yamada, T. & Kawahara, A. (1994). Acta Cryst. C50, 986–988. CrossRef CAS Web of Science IUCr Journals Google Scholar

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