research communications\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

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ISSN: 2056-9890

Crystal structure of Na4Co7−xAl0.67x(As1−yPyO4)6 (x = 1.60; y = 0.116)

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aUniversité de Tunis El Manar, Faculté des Sciences, Laboratoire de Matériaux, Cristallochimie et Thermodynamique Appliquée, El Manar II, 2092 Tunis, Tunisia, bUniversité de Tunis, Institut Préparatoire aux Etudes d'Ingénieurs de Tunis, Rue Jawaher Lel Nehru, 1089 Montfleury, Tunis, Tunisia, and cAl-Baha University, Faculty of Sciences and Arts in Al Mukhwah, Al Mukhwah, Al Baha Region, Kingdom of Saudi Arabia
*Correspondence e-mail: abderrahmen.guesmi@ipeim.rnu.tn

Edited by I. D. Brown, McMaster University, Canada (Received 3 March 2016; accepted 9 March 2016; online 15 March 2016)

The title compound, tetra­sodium hepta­(cobalt/aluminium) hexa­(arsenate/phosphate), Na4Co5.40Al1.07(As0.883P0.116O4)6, was prepared by a solid-state reaction. It is a new member of the family of isostructural compounds with the general formula A4M7(XO4)6 (A: Na, K; M: Ni, Co; X: P, As) that is most similar to Na4Co5.63Al0.91(AsO4)6. The Co2+ ions in the title compound are substituted by Al3+ in a fully occupied octa­hedral site (site symmetry 2/m) and a partially occupied tetra­hedral site (site symmetry 2). A third octa­hedral site is fully occupied by Co2+ ions only. With regard to the P and As atoms, one site (site symmetry m) is simultaneously occupied by As and P, whereas in the second site there is only arsenic. The alkali cations are, as in the isostructural compounds, distributed over half-occupied crystallographic sites, with a positional disorder of one of them. The proposed structural model is based both on a careful investigation of the crystal data, as well as validation by means of bond-valence-sum (BVS) and charge-distribution (CHARDI) calculations. The correlation between the X-ray refinement and the validation results is discussed.

1. Chemical context

Metal-substituted aluminophosphates and aluminoarsenates form an important group of materials with many inter­esting properties such as mol­ecular sieves, catalysts, etc. Li et al. (2012[Li, J., Yu, J. & Xu, R. (2012). Proc. R. Soc. A, 468, 1955-1967.]) reported the progress in heteroatom-containing alumino­phosphate mol­ecular sieves. With regard to their As homologues, one can cite AlAsO4-5 and AlAsO4-6, two aluminoarsenates with occluded ethyl­enedi­amine (Chen et al. 1990[Chen, J., Xu, R., Xu, Y. & Qiu, J. (1990). J. Chem. Soc. Dalton Trans. pp. 3319-3323.]). The analogous cobalt compounds, such as ammonium-templated cobalt aluminophosphates with zeolite-like structures (Bontchev & Sevov, 1999[Bontchev, R. P. & Sevov, S. C. (1999). J. Mater. Chem. 9, 2679-2682.]), possess similar structural properties.

The title compound, Na4Co7−xAl0.67x(As1−yPyO4)6 (x = 1.60; y = 0.116), was obtained during the exploration of the Na–Co–P–As–O system by solid-state reaction; as for many aluminophosphates, aluminum was incorporated from the reaction container. The chemical composition and crystal structure were determined by energy-dispersive X-ray spectroscopy (EDX) analysis (Fig. 1[link]) and single-crystal X-ray diffraction; the proposed structural model is supported by validation tools by means of bond-valence-sum (BVS) calculations and charge-distribution (CHARDI) analysis (Brown, 2002[Brown, I. D. (2002). The Chemical Bond in Inorganic Chemistry - The Bond Valence Model. IUCr Monographs on Crystallography, 12. Oxford University Press.]; Adams, 2003[Adams, S. (2003). softBV. University of Göttingen, Germany. https://kristall.uni-mki. gwdg. de/softBV/.], Nespolo, 2015[Nespolo, M. (2015). CHARDI-2015. https://www.crystallography.fr/chardi.], 2016[Nespolo, M. (2016). Acta Cryst. B72, 51-66.]; Eon & Nespolo, 2015[Eon, J.-G. & Nespolo, M. (2015). Acta Cryst. B71, 34-47.]). The correlation between the experimental and the validation results is discussed.

[Figure 1]
Figure 1
The EDX spectrum of the title compound. The inset shows the morphology of one crystal.

2. Structural commentary

The title compound is a new member of the isostructural compounds family with the general formula A4M7(XO4)6 (A: Na, K; M: Ni, Co; X: P, As) (Moring & Kostiner, 1986[Moring, J. & Kostiner, E. (1986). J. Solid State Chem. 62, 105-111.]; Kobashi et al., 1998[Kobashi, D., Kohara, S., Yamakawa, J. & Kawahara, A. (1998). Acta Cryst. C54, 7-9.]; Ben Smail et al., 1999[Ben Smail, R., Driss, A. & Jouini, T. (1999). Acta Cryst. C55, 284-286.]; Marzouki et al., 2010[Marzouki, R., Guesmi, A. & Driss, A. (2010). Acta Cryst. C66, i95-i98.], 2013[Marzouki, R., Guesmi, A., Zid, M. F. & Driss, A. (2013). J. Inorg. Chem. pp. 9-16.]).

The asymmetric unit of the title compound (I) (Fig. 2[link]) contains seven metallic sites of which four are occupied by Na+ cations (occupancies ranging from 0.23 to 0.50) with eight cations per unit cell, two others (denoted MA and MB) are simultaneously shared by Co2+ and Al3+ ions, and one is fully occupied by Co2+ ions: the same distribution is observed in the homologous arsenate Na4Co7−xAl0.67x(AsO4)6 (x = 1.37) (II) (Marzouki et al., 2010[Marzouki, R., Guesmi, A. & Driss, A. (2010). Acta Cryst. C66, i95-i98.]).

[Figure 2]
Figure 2
The asymmetric unit of (I), showing the atom-labelling scheme. The full coordination polyhedra are shown, including the corresponding symmetry-related O atoms. Displacement ellipsoids are drawn at the 50% probability level. [MA = Co0.189Al0.811; MB = Co0.605Al0.1350.260; MC = As0.65P0.35. Symmetry codes: (i) x, −y, z; (ii) −x, y, −z; (iii) −x, −y, −z; (iv) −[{1\over 2}] − x, [{1\over 2}] − y, z; (v) −[{1\over 2}] − x, [{1\over 2}] − y, −z; (vi) −1 − x, y, −z.]

3. Validation of the structural model using BVS and CHARDI

Two validation tools, BVS and CHARDI, are used to support and analyse the proposed structural model. Briefly, for a properly refined structure, the valences V according to the BVS model and charges Q from the CHARDI analysis should agree with the oxidation states of the atoms (Brown, 2002[Brown, I. D. (2002). The Chemical Bond in Inorganic Chemistry - The Bond Valence Model. IUCr Monographs on Crystallography, 12. Oxford University Press.]; Adams, 2003[Adams, S. (2003). softBV. University of Göttingen, Germany. https://kristall.uni-mki. gwdg. de/softBV/.], Nespolo, 2015[Nespolo, M. (2015). CHARDI-2015. https://www.crystallography.fr/chardi.], 2016[Nespolo, M. (2016). Acta Cryst. B72, 51-66.]; Eon & Nespolo, 2015[Eon, J.-G. & Nespolo, M. (2015). Acta Cryst. B71, 34-47.]).

The MA site, with an octa­hedral environment by oxygen atoms, is fully occupied by the two cations with overall occupancy Co0.189Al0.811. This distribution scheme is confirmed by the validation tools, with a better convergence with the CHARDI model (Table 1[link]). If compared to the homologous site in (II) with overall occupancy Co0.286Al0.714 (Marzouki et al., 2010[Marzouki, R., Guesmi, A. & Driss, A. (2010). Acta Cryst. C66, i95-i98.]), the average arithmetic distance in (I) (1.91 Å) is smaller than in (II) (1.96 Å) due to the higher fraction of the small cation (Al3+) in (I).

Table 1
BVS and CHARDI analysis of cation polyhedra in the title compound (the structure described as being built of cation-centred polyhedra)

Cation q(i)·sofi Vi Qi CNi ECoNi
MA 2.81 2.97 2.91 6 5.92
MB 1.61 1.31 1.58 4 3.95
Co3 2.00 2.05 1.99 6 5.88
MC 5.00 5.21 5.00 4 3.97
As2 5.00 5 5.09 4 3.98
Na1 0.50 0.51 0.49 5 4.53
Na2 0.50 0.52 0.49 7 6.18
Na31 0.23 0.23 0.23 7 6.06
Na32 0.27 0.28 0.27 6 5.31
Notes: MA = Co0.189Al0.811; MB = Co0.605Al0.1350.260; Mc = As0.65P0.35; q is the formal oxidation number; sof is the site-occupation factor; MAPD = 1% [the mean absolute percentage deviation MAPD measures the agreement between q and Q; for more information, see Nespolo (2016[Nespolo, M. (2016). Acta Cryst. B72, 51-66.])].

For the MB site with a tetra­hedral coordination, the Co2+/Al3+ distribution is based on the same observations as in (II), mainly if it is refined as partially occupied by just Co2+, the charge neutrality is not achieved, and then a fraction of Al3+ was introduced in the MB site yielding an overall occupancy distribution of Co0.605Al0.1350.260, with □ expressing the vacancy. The validation results for this particular distribution are: V(MB) = 1.31 and Q(MB) = 1.58, the theoretical value is 1.61 (Table 1[link]). Finally, with regard to P and As atoms, the P/As substitutional disorder is observed in one of the two sites (MC): P/As = 0.35/0.65; V = 5.21 and Q = 5.00.

The final result corresponds to the formula Na4Co5.40Al1.07(As0.883P0.116O4)6. It is the first case in its homologous family which contains such a number of elements. The similarity to (II) (Marzouki et al., 2010[Marzouki, R., Guesmi, A. & Driss, A. (2010). Acta Cryst. C66, i95-i98.]) is clear, the cell parameters of (I) are smaller than those of (II) as it contains more small elements than (II). The CHARDI method is extended, as for (II), to analyse the coordination polyhedra by means of the Effective Coordination Numbers (ECoN): the polyhedron distortion is more pronounced if the ECoN deviates more from the classical coordination number (CN).

The framework of the title compound is of an open character (Fig. 3[link]). Its aptitude for sodium conduction through the tunnels appears to be possible, as shown in experimental and theoretical studies for the similar compound (II) (Marzouki et al., 2013[Marzouki, R., Guesmi, A., Zid, M. F. & Driss, A. (2013). J. Inorg. Chem. pp. 9-16.]). These studies will be the subject of future works.

[Figure 3]
Figure 3
The structure of the title compound viewed appoximately along [100], showing the tunnels and the Na+ cations.

4. Synthesis and crystallization

A mixture of sodium nitrate, cobalt nitrate hexa­hydrate, NH4H2XO4 (X: P, As) in the molar ratio Na:Co:P:As = 2:1:0.5:1 was dissolved in deionized water and then heated at 373 K to dehydration. After grinding, it was placed in a porcelain boat and first heated at 673 K in air for 24 h and then heated gradually to 1123 K for 1 d. Some pink parallelepiped-shaped crystals were isolated from the sample. A qualitative EDX analysis confirmed the presence of Na, Co, Al, As and O (Fig. 1[link]), with the aluminium diffusing from the reaction container.

5. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2[link]. The Co and Al atoms occupying the MA and MB sites, as well as the P and As atoms occupying the MC site, were constrained using the EXYZ and EADP instructions of SHELXL97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]). Three linear free variable restraints (SUMP) were required to restrain the sum of their occupation factors. The Na1 and Na2 cations are at half-occupancy sites and the two others (Na31 and Na32) with isotropic refinement have a total occupancy of 0.50 because, when refined freely, their occupations converged to these values.

Table 2
Experimental details

Crystal data
Chemical formula Na4Co5.40Al1.07(As0.883P0.116O4)6
Mr 1242.08
Crystal system, space group Monoclinic, C2/m
Temperature (K) 293
a, b, c (Å) 10.5797 (2), 14.5528 (3), 6.6441 (3)
β (°) 105.608 (9)
V3) 985.23 (7)
Z 2
Radiation type Mo Kα
μ (mm−1) 13.60
Crystal size (mm) 0.30 × 0.20 × 0.20
 
Data collection
Diffractometer Enraf–Nonius CAD-4
Absorption correction ψ scan (North et al., 1968[North, A. C. T., Phillips, D. C. & Mathews, F. S. (1968). Acta Cryst. A24, 351-359.])
Tmin, Tmax 0.055, 0.140
No. of measured, independent and observed [I > 2σ(I)] reflections 2409, 1124, 894
Rint 0.027
(sin θ/λ)max−1) 0.638
 
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.030, 0.083, 1.07
No. of reflections 1124
No. of parameters 117
No. of restraints 2
Δρmax, Δρmin (e Å−3) 0.81, −0.85
Computer programs: CAD-4 EXPRESS (Duisenberg, 1992[Duisenberg, A. J. M. (1992). J. Appl. Cryst. 25, 92-96.]; Macíček & Yordanov, 1992[Macíček, J. & Yordanov, A. (1992). J. Appl. Cryst. 25, 73-80.]), XCAD4 (Harms & Wocadlo, 1995[Harms, K. & Wocadlo, S. (1995). XCAD4. University of Marburg, Germany.]), SHELXS97 and SHELXL97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]), DIAMOND (Brandenburg, 2006[Brandenburg, K. (2006). DIAMOND. Crystal Impact GbR, Bonn, Germany.]), WinGX (Farrugia, 2012[Farrugia, L. J. (2012). J. Appl. Cryst. 45, 849-854.]) and publCIF (Westrip, 2010[Westrip, S. P. (2010). J. Appl. Cryst. 43, 920-925.]).

Supporting information


Computing details top

Data collection: CAD-4 EXPRESS (Duisenberg, 1992; Macíček & Yordanov, 1992); cell refinement: CAD-4 EXPRESS (Duisenberg, 1992; Macíček & Yordanov, 1992); data reduction: XCAD4 (Harms & Wocadlo, 1995); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2006); software used to prepare material for publication: WinGX (Farrugia, 2012) and publCIF (Westrip, 2010).

Tetrasodium hepta(cobalt/aluminium) hexa(arsenate/phosphate) top
Crystal data top
Na4Co5.40Al1.07(As0.883P0.116O4)6F(000) = 1162
Mr = 1242.08Dx = 4.187 Mg m3
Monoclinic, C2/mMo Kα radiation, λ = 0.71073 Å
a = 10.5797 (2) ÅCell parameters from 25 reflections
b = 14.5528 (3) Åθ = 12.0–14.8°
c = 6.6441 (3) ŵ = 13.60 mm1
β = 105.608 (9)°T = 293 K
V = 985.23 (7) Å3Parallelepiped, pink
Z = 20.30 × 0.20 × 0.20 mm
Data collection top
Enraf–Nonius CAD-4
diffractometer
Rint = 0.027
ω/2θ scansθmax = 27.0°, θmin = 2.4°
Absorption correction: ψ scan
(North et al., 1968)
h = 1313
Tmin = 0.055, Tmax = 0.140k = 118
2409 measured reflectionsl = 88
1124 independent reflections2 standard reflections every 120 reflections
894 reflections with I > 2σ(I) intensity decay: 1%
Refinement top
Refinement on F2117 parameters
Least-squares matrix: full2 restraints
R[F2 > 2σ(F2)] = 0.030 w = 1/[σ2(Fo2) + (0.0401P)2 + 10.5538P]
where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.083(Δ/σ)max < 0.001
S = 1.07Δρmax = 0.81 e Å3
1124 reflectionsΔρmin = 0.85 e Å3
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
xyzUiso*/UeqOcc. (<1)
Co10.00000.00000.00000.0064 (9)0.189 (13)
Al10.00000.00000.00000.0064 (9)0.811 (13)
Co20.50000.16324 (13)0.00000.0118 (6)0.605 (9)
Al20.50000.16324 (13)0.00000.0118 (6)0.135 (9)
Co30.18046 (7)0.18027 (5)0.17925 (10)0.0062 (2)
As10.32397 (10)0.00000.06479 (16)0.0091 (4)0.649 (7)
P10.32397 (10)0.00000.06479 (16)0.0091 (4)0.351 (7)
As20.09963 (5)0.17931 (4)0.29004 (8)0.00940 (18)
Na10.4220 (5)0.1148 (4)0.5048 (8)0.0258 (12)0.5
Na20.6741 (7)0.00000.4195 (11)0.0217 (16)0.5
Na310.084 (3)0.00000.469 (3)0.017 (2)*0.229 (19)
Na320.036 (2)0.00000.487 (2)0.017 (2)*0.271 (19)
O10.0101 (4)0.0937 (3)0.2026 (6)0.0090 (8)
O20.3346 (4)0.0895 (3)0.0802 (6)0.0127 (8)
O30.0063 (4)0.2670 (3)0.2696 (6)0.0100 (8)
O40.1921 (4)0.2070 (3)0.1327 (6)0.0111 (8)
O50.4356 (6)0.00000.2789 (10)0.0202 (14)
O60.1900 (4)0.1511 (3)0.5228 (6)0.0134 (9)
O70.1813 (6)0.00000.1116 (10)0.0141 (13)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Co10.0061 (14)0.0053 (15)0.0075 (14)0.0000.0013 (9)0.000
Al10.0061 (14)0.0053 (15)0.0075 (14)0.0000.0013 (9)0.000
Co20.0103 (8)0.0146 (10)0.0102 (9)0.0000.0021 (6)0.000
Al20.0103 (8)0.0146 (10)0.0102 (9)0.0000.0021 (6)0.000
Co30.0065 (3)0.0070 (4)0.0048 (3)0.0004 (3)0.0007 (3)0.0005 (3)
As10.0070 (5)0.0067 (6)0.0131 (6)0.0000.0019 (4)0.000
P10.0070 (5)0.0067 (6)0.0131 (6)0.0000.0019 (4)0.000
As20.0090 (3)0.0115 (3)0.0070 (3)0.0007 (2)0.0010 (2)0.0008 (2)
Na10.026 (3)0.020 (3)0.027 (3)0.005 (2)0.001 (2)0.011 (2)
Na20.022 (4)0.029 (5)0.018 (4)0.0000.012 (3)0.000
O10.0112 (17)0.0083 (19)0.0072 (18)0.0014 (15)0.0018 (14)0.0006 (16)
O20.0149 (19)0.011 (2)0.0122 (19)0.0039 (16)0.0043 (15)0.0052 (17)
O30.0076 (18)0.010 (2)0.0112 (19)0.0023 (16)0.0002 (14)0.0004 (16)
O40.0150 (19)0.016 (2)0.0041 (18)0.0056 (17)0.0050 (15)0.0040 (16)
O50.019 (3)0.016 (4)0.022 (3)0.0000.000 (3)0.000
O60.0145 (19)0.023 (2)0.0022 (17)0.0030 (18)0.0009 (15)0.0017 (16)
O70.009 (3)0.011 (3)0.023 (3)0.0000.006 (2)0.000
Geometric parameters (Å, º) top
Co1—O7i1.861 (6)Na2—Na1ix2.086 (8)
Co1—O71.861 (6)Na2—Na1xi2.086 (8)
Co1—O11.939 (4)Na2—O52.443 (10)
Co1—O1i1.939 (4)Na2—Na31xii2.49 (3)
Co1—O1ii1.939 (4)Na2—O5ix2.572 (10)
Co1—O1iii1.939 (4)Na2—O2iv2.584 (7)
Co2—O2iv1.999 (4)Na2—O2xii2.584 (7)
Co2—O21.999 (4)Na2—O6xiii2.598 (6)
Co2—O3v2.075 (4)Na2—O6xiv2.598 (6)
Co2—O3vi2.075 (4)Na2—Na32xii2.98 (2)
Co3—O6vii2.054 (4)Na31—Na32xv1.23 (5)
Co3—O22.064 (4)Na31—Na31xv1.72 (6)
Co3—O4iii2.080 (4)Na31—O6xv2.473 (15)
Co3—O4v2.092 (4)Na31—O6vii2.473 (15)
Co3—O12.171 (4)Na31—Na2xii2.49 (3)
Co3—O32.181 (4)Na31—O12.524 (17)
As1—O51.586 (6)Na31—O1ii2.524 (17)
As1—O71.621 (6)Na31—O1vii2.536 (17)
As1—O2ii1.642 (4)Na31—O1xv2.536 (17)
As1—O21.642 (4)Na32—Na32xv0.73 (4)
As2—O61.637 (4)Na32—Na31xv1.23 (5)
As2—O41.662 (4)Na32—O1vii2.408 (13)
As2—O31.680 (4)Na32—O1xv2.408 (13)
As2—O11.695 (4)Na32—O12.407 (13)
Na1—O52.276 (7)Na32—O1ii2.407 (13)
Na1—O3viii2.298 (7)Na32—O6xv2.727 (14)
Na1—O5ix2.441 (7)Na32—O6vii2.727 (14)
Na1—O6i2.545 (7)Na32—Na2xii2.98 (2)
Na1—O3x2.572 (8)
O7i—Co1—O7180.0O2iv—Co2—O3vi105.15 (15)
O7i—Co1—O188.09 (17)O2—Co2—O3vi105.29 (15)
O7—Co1—O191.91 (17)O3v—Co2—O3vi121.5 (2)
O7i—Co1—O1i91.91 (17)O6vii—Co3—O286.29 (16)
O7—Co1—O1i88.09 (17)O6vii—Co3—O4iii173.90 (16)
O1—Co1—O1i180.0O2—Co3—O4iii88.41 (16)
O7i—Co1—O1ii88.09 (17)O6vii—Co3—O4v96.19 (16)
O7—Co1—O1ii91.91 (17)O2—Co3—O4v91.84 (17)
O1—Co1—O1ii89.4 (2)O4iii—Co3—O4v80.95 (17)
O1i—Co1—O1ii90.6 (2)O6vii—Co3—O193.80 (16)
O7i—Co1—O1iii91.91 (17)O2—Co3—O1102.77 (16)
O7—Co1—O1iii88.09 (17)O4iii—Co3—O190.31 (15)
O1—Co1—O1iii90.6 (2)O4v—Co3—O1162.79 (16)
O1i—Co1—O1iii89.4 (2)O6vii—Co3—O396.40 (16)
O1ii—Co1—O1iii180.0 (3)O2—Co3—O3174.29 (16)
O2iv—Co2—O2115.1 (3)O4iii—Co3—O389.15 (16)
O2iv—Co2—O3v105.29 (15)O4v—Co3—O392.87 (16)
O2—Co2—O3v105.15 (15)O1—Co3—O372.08 (15)
Symmetry codes: (i) x, y, z; (ii) x, y, z; (iii) x, y, z; (iv) x1, y, z; (v) x1/2, y+1/2, z; (vi) x1/2, y+1/2, z; (vii) x, y, z+1; (viii) x1/2, y1/2, z1; (ix) x1, y, z1; (x) x1/2, y1/2, z; (xi) x1, y, z1; (xii) x1, y, z; (xiii) x1, y, z1; (xiv) x1, y, z1; (xv) x, y, z+1.
BVS and CHARDI analysis of cation polyhedra in the title compound (structure described as being built of cation-centred polyhedra) top
Cationq(i)·sofiViQiCNiECoNi
MA2.812.972.9165.92
MB1.611.311.5843.95
Co32.002.051.9965.88
MC5.005.215.0043.97
As25.0055.0943.98
Na10.500.510.4954.53
Na20.500.520.4976.18
Na310.230.230.2376.06
Na320.270.280.2765.31
Notes: MA = Co0.189Al0.811; MB = Co0.605Al0.1350.260; Mc = As0.65P0.35; q is the formal oxidation number; sof is the site-occupation factor; MAPD = 1% [the mean absolute percentage deviation MAPD measures of the agreement between q and Q; for more information, see Nespolo (2016)].
 

Acknowledgements

The authors are grateful to Professor M. F. Zid, Université Tunis El Manar, Faculté des Sciences, for the X-ray data and to Professor M. Nespolo, Kyoto University, Faculty of Sciences, for fruitful discussions.

References

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