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Redetermination and new description of the crystal structure of vanthoffite, Na6Mg(SO4)4

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aUniversity of Copenhagen, Department of Geosciences, Denmark, and bDepartment of Geosciences, University of Padova, Italy
*Correspondence e-mail: toncib@ign.ku.dk

Edited by M. Weil, Vienna University of Technology, Austria (Received 1 April 2020; accepted 28 April 2020; online 1 May 2020)

The crystal structure of vanthoffite {hexa­sodium magnesium tetra­kis[sulfate­(VI)]}, Na6Mg(SO4)4, was solved in the year 1964 on a synthetic sample [Fischer & Hellner (1964[Fischer, W. & Hellner, E. (1964). Acta Cryst. 17, 1613.]). Acta Cryst. 17, 1613]. Here we report a redetermination of its crystal structure on a mineral sample with improved precision. It was refined in the space group P21/c from a crystal originating from Surtsey, Iceland. The unique Mg (site symmetry [\overline{1}]) and the two S atoms are in usual, only slightly distorted octa­hedral and tetra­hedral coordinations, respectively. The three independent Na atoms are in a distorted octa­hedral coordination (1×) and distorted 7-coordinations inter­mediate between a `split octa­hedron' and a penta­gonal bipyramid (2×). [MgO6] coordination polyhedra inter­change with one half of the sulfate tetra­hedra in <011> chains forming a (100) meshed layer, with dimers formed by edge-sharing [NaO7] polyhedra filling the inter­chain spaces. The other [NaO7] polyhedra are organized in a parallel layer formed by [010] and [001] chains united through edge sharing and bonds to the remaining half of sulfate groups and to [NaO6] octa­hedra. The two types of layers inter­connect through tight bonding, which explains the lack of morphological characteristics typical of layered structures.

1. Chemical context

Vanthoffite is an evaporitic mineral that occurs worldwide in various salt, potash and sulfate marine deposits. It is also reported from the fumaroles of Kamchatka (Pekov et al., 2015[Pekov, I. V., Zubkova, N. V., Yapaskurt, V. O., Britvin, S. N., Vigasina, M. F., Sidorov, E. G. & Pushcharovsky, D. Y. (2015). Eur. J. Mineral. 27, 581-588.]) and Iceland (Balić-Žunić et al., 2016[Balić-Žunić, T., Garavelli, A., Jakobsson, S. P., Jonasson, K., Katerinopoulos, A., Kyriakopoulos, K. & Acquafredda, P. (2016). In: Updates in Volcanology - From Volcano Modelling to Volcano Geology, edited by K. Nemeth. London: InTechOpen. DOI: 10.5772/64129.]). Fischer & Hellner (1964[Fischer, W. & Hellner, E. (1964). Acta Cryst. 17, 1613.]) solved its crystal structure giving the crystal lattice parameters, space group and atomic coordinates with isotropic atomic displacement parameters. To the best of our knowledge the only other crystal structure determination and refinement of an isostructural compound is for Na6Mn(SO4)4 (Sharma et al., 2017[Sharma, V., Swain, D. & Guru Row, T. N. (2017). Inorg. Chem. 56, 6048-6051.]).

Here we report a redetermination and refinement of the crystal structure of vanthoffite, complete with anisotropic displacement parameters and provide a more detailed description. The precision of the present results is significantly better compared to the previous data of Fischer & Hellner (1964[Fischer, W. & Hellner, E. (1964). Acta Cryst. 17, 1613.]) because of the capabilities of modern X-ray diffraction equipment based on a hybrid photon-counting detector. The obtained R factor for the observed reflection data is 3.2% compared to 6.4% for the previous refinement, and the standard deviations of the atomic coordinates and displacement parameters are three to five times smaller. Consequently, the standard deviations of bond lengths and angles are generally ten or more times smaller than previously reported. Comparing our results with those of Fischer & Hellner (1964[Fischer, W. & Hellner, E. (1964). Acta Cryst. 17, 1613.]), we conclude that no differences of substantial character can be observed, and this pays a special credit to the latter work done with significantly more effort than needed for the present one. The improvement in precision that we obtained, however, allows us to evaluate important structural details that were until now lacking for vanthoffite.

2. Structural commentary

In this work, we use three distortion parameters for the description of deviations of atomic coordinations from an ideal geometrical arrangement, viz. asphericity, eccentricity and volume distortion, as defined by Balić-Žunić & Makovicky (1996[Balić Žunić, T. & Makovicky, E. (1996). Acta Cryst. B52, 78-81.]), and Makovicky & Balić-Žunić (1998[Makovicky, E. & Balić-Žunić, T. (1998). Acta Cryst. B54, 766-773.]). Numerical values of these parameters are collated in Table 1[link]. They are useful because they clearly define the type and reason for distortion (in the case of a Jahn–Teller effect or the presence of lone electron pairs), and at the same time define the closest type of the coordination polyhedron.

Table 1
The parameters of the coordination polyhedra calculated with the program IVTON (Balić-Žunić & Vicković, 1996[Balić Žunić, T. & Vicković, I. (1996). J. Appl. Cryst. 29, 305-306.])

Cation CN <d> (Å) bvs Vp (Å3) vd asp ecc
S1 4 1.474 6.002 1.643 (4) 0.0003 0 0.0115
S2 4 1.473 6.027 1.637 (4) 0.0006 0 0.0124
Mg 6 2.083 2.094 11.99 (2) 0.0046 0.0060 0
Na1 6 2.408 1.177 17.18 (2) 0.0716 0.0119 0.0392
Na2 7 2.561 1.074 24.64 (4) 0.0674 0.0586 0.0480
Na3 7 2.524 1.071 22.76 (3) 0.0957 0.0602 0.1492
Notes: CN = coordination number; <d> = average bond length; bvs = bond valence sum, calculated using the exponential function of Brown & Altermatt (1985[Brown, I. D. & Altermatt, D. (1985). Acta Cryst. B41, 244-247.]) with the parameters of Brese & O'Keeffe (1991[Brese, N. E. & O'Keeffe, M. (1991). Acta Cryst. B47, 192-197.]); Vp = polyhedral volume; vd = volume distortion; asp = asphericity; ecc = eccentricity.

2.1. Coordination polyhedra of Mg and S atoms

The unique Mg atom is located on a symmetry centre and is octa­hedrally coordinated by O atoms, whereas the two independent S atoms form tetra­hedral sulfate groups with oxygen atoms (Fig. 1[link]). The coordinations of Mg and S show very small distortions from the ideal octa­hedral and tetra­hedral arrangements, respectively. As can be seen from Table 1[link], both S coordination polyhedra have very similar parameters. They are slightly eccentric; the longest bonds are to the O atoms that they share with Mg. This is plausible, because Mg has a larger electronegativity and a higher charge than Na. The Mg coordination polyhedron is even less distorted than those of S. The eccentricity is zero, in accordance with the site being on a symmetry centre and the other two distortion parameters are very low. The anisotropy of the displacement parameters of oxygen atoms bonded to S and Mg, with the overall oblate character of their ellipsoids and the longest diameters approximately perpendicular to the bonding directions, suggests, together with a low anisotropy of S and Mg displacement parameters, a rotational displacement of the coord­ination polyhedra around their centres (Fig. 1[link]). Each of the vertices of an [MgO6] octa­hedron is shared with one sulfate tetra­hedron, in an arrangement known as a pinwheel structure (Moore, 1973[Moore, P. B. (1973). Am. Mineral. 58, 32-42.]).

[Figure 1]
Figure 1
The atomic grouping around the [MgO6] coordination polyhedron. Anisotropic displacement ellipsoids are drawn at the 50% probability level.

2.2. Coordination polyhedra of Na atoms

The coordination environment for Na atoms is distorted octa­hedral in the case of Na1 and split-octa­hedral with a coordination number (CN) of 7 for the other two independent Na sites (Figs. 2[link] and 3[link]). We consider only the O atoms closer than 3 Å to be bonded to Na. There are further O atoms in the neighbourhood of Na, listed by Fischer & Hellner (1964[Fischer, W. & Hellner, E. (1964). Acta Cryst. 17, 1613.]), but we note that the distance gap to these additional O atoms is significant and their bonding contribution negligible according to bond-valence calculations. The volume distortions of the coordination polyhedra around Na2 and Na3 lie between those of an ideal penta­gonal bipyramid (0) and an ideal `split octa­hedron' (0.1333). The latter type of coordination was described in detail by Edenharter (1976[Edenharter, A. (1976). Schweiz. Miner. Petro. Mitt. 56, 195-217.]) and Makovicky & Balić-Žunić (1998[Makovicky, E. & Balić-Žunić, T. (1998). Acta Cryst. B54, 766-773.]). The coordination polyhedron of Na2 (Fig. 2[link]) can either be described as a penta­gonal bipyramid with O4 and O6 as polar vertices, or as a split octa­hedron with O5 and O8 as a split vertex. Likewise, the coordination polyhedron of Na3 (Fig. 3[link]) can either be described as a distorted penta­gonal bipyramid with O2 and O6 as polar vertices, or as a split octa­hedron with the second O2 and O5 as a split vertex. It can, furthermore, be seen from Figs. 2[link] and 3[link] that coordination polyhedra of Na2 and Na3 each share two edges with sulfate tetra­hedra. Edges O5–O8 and O6–O8 of [Na2O7] are shared with two [S2O4] tetra­hedra, whereas edges O2–O3 and O5–O7 of [Na3O7] are shared with a S1 and a S2 coordination tetra­hedron, respectively.

[Figure 2]
Figure 2
Atomic coordination of the Na2 atom. Displacement ellipsoids are as in Fig. 1[link]. [Symmetry codes: (i) 1 − x, −[{1\over 2}] + y, [{1\over 2}] − z; (v) x, [{1\over 2}] − y, −[{1\over 2}] + z].
[Figure 3]
Figure 3
Atomic coordination of the Na3 atom. Displacement ellipsoids are as in Fig. 1[link]. [Symmetry codes: (i) 1 − x, −[{1\over 2}] + y, [{1\over 2}] − z; (v) x, [{1\over 2}] − y, −[{1\over 2}] + z; (viii) 1 + x, y, z; (ix) 1 + x, [{1\over 2}] − y, [{1\over 2}] + z].

2.3. Description of the crystal structure as an arrangement of coordination polyhedra of cations

The crystal structure of vanthoffite can be described as an inter­change of two types of layers parallel to {100}, here labelled A and B (Figs. 4[link] and 5[link]). Layer A is centred on the (0, y, z) plane and built of coordination polyhedra of Mg, S1 and Na3 (Fig. 6[link]). [MgO6] octa­hedra share four vertices with four [S1O4] tetra­hedra. They form inter­secting chains running along the <011> directions. Sharma et al. (2017[Sharma, V., Swain, D. & Guru Row, T. N. (2017). Inorg. Chem. 56, 6048-6051.]) described the crystal structure of the vanthoffite type as having an infinite two-dimensional framework of Mg coordination polyhedra and sulphate groups in the bc plane (which we confirm), but describe this framework as being composed of inter­connected chains parallel to [010], which is an obvious mistake, as can be seen from Fig. 6[link]. In layer A, [Na3O7] coordination polyhedra are arranged in pairs that share a common edge (O2–O2′). If we consider the coordination polyhedra of Mg and Na3 alone, they form chains parallel to [001] in which the Mg and Na coordination polyhedra also share edges (O1–O3). The chains inter­connect through common O7 vertices, belonging to both the Mg and Na3 coordination polyhedra. The [Na3O7] polyhedron also shares its O2–O3 edge with an [S1O4] tetra­hedron as mentioned above, plus an O1 vertex with another [S1O4] tetra­hedron.

[Figure 4]
Figure 4
Projection of the crystal structure of vanthoffite along [001] with indication of the A and B structural layers.
[Figure 5]
Figure 5
Projection of the crystal structure of vanthoffite along [010] with indication of the A and B structural layers.
[Figure 6]
Figure 6
Layer A formed by the coordination polyhedra of Mg, S1 and Na3, projected on (100), with the c axis vertical. Attachment of S2 and Na1, both visualized as spheres, is shown.

Layer B is centred on the (1/2, y, z) plane and built of coordination polyhedra of Na1, Na2 and S2 (Fig. 7[link]). [Na2O7] coordination polyhedra form chains around the c symmetry planes, by sharing O4 vertices. These chains run along [001]. They also form chains along [010] and around 21 axes by sharing O8 vertices. The two types of chains inter­connect by sharing O6–O6′ edges, in the middle of which are situated symmetry centres. As mentioned above, [S2O4] tetra­hedra, located in this layer, share two edges (O5–O8 and O6–O8) with [Na2O7] polyhedra. Na1 atoms lie in distorted octa­hedral holes formed between neighbouring A and B layers. The corresponding [Na1O6] octa­hedra share O4–O8 and O5–O8 edges with [Na2O7] and O2–O5 edges with [Na3O7]. There are further inter­connections between the two types of layers (O5–O6 edges shared by Na3 and Na2, O5–O7 edges shared by Na3 and S2, plus several shared vertices).

[Figure 7]
Figure 7
Layer B formed by the coordination polyhedra of Na1, Na2 and S2, projected on (100), with the c axis vertical. To enhance clarity, the coordination polyhedra of Na1 are not filled; attachment of S1 visualized as a sphere is shown.

Fischer & Hellner (1964[Fischer, W. & Hellner, E. (1964). Acta Cryst. 17, 1613.]) described the crystal structure of vanthoffite as a distorted hexa­gonal close packing of sulfate groups, with Mg in ¼ of the octa­hedral holes. The authors did not specify the orientation of the close-packed sulfate layers. There are indeed approximately eutactic layers of sulfate groups parallel to the (001) plane. Their composition and stacking, however, deviate considerably from an ideal eutaxy. Moreover, considering the full framework of coordination polyhedra and chemical bonds, the structure is best described as layered parallel to (100) as in this work and in Hawthorne et al. (2000[Hawthorne, F. C., Krivovichev, S. V. & Burns, P. C. (2000). Rev. Mineral. Geochem. 40, 1-112.]). Most of the previous authors essentially ignored the function of the [NaOx] coordination polyhedra in building the crystal structure, and just mentioned the placement of Na in the holes of the framework of the Mg and S coordination polyhedra. Only Fischer (1973[Fischer, W. (1973). Z. Kristallogr. 137, 445-446.]) discussed the three Na coordination types in this structure in a conference abstract. Since Na is the dominating cation in vanthoffite, the structure-building role of the [NaOx] coordination polyhedra also needs to be considered, as we have tried to do in this article.

Vanthoffite is characterized by having six times as many Na atoms as Mg ones. The availability of Na coordination polyhedra in close contact, defining a three-dimensional framework, makes it a potential Na+ ionic conductor. Sharma et al. (2017[Sharma, V., Swain, D. & Guru Row, T. N. (2017). Inorg. Chem. 56, 6048-6051.]) found a high Na+ conductivity only in the material obtained after the transition of vanthoffite-type Na6Mn(SO4)4 to a high-temperature phase. We hope that the present detailed description can help in understanding why Na+ conductivity is observed in the high-temperature form only (once its structure is known), but not in the vanthoffite structure itself.

3. Synthesis and crystallization

The crystal used for the crystal structure analysis originates from a sample from Surtsey, collected in 1971 by Dr Svein Peter Jakobsson from the Icelandic Institute of Natural History, four years after the end of eruption that formed this volcanic island. The sample number in the mineral collection of the Institute is IN7484.

4. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2[link]. Atomic sites were labelled to correspond to the original description of the crystal structure (Fischer & Hellner, 1964[Fischer, W. & Hellner, E. (1964). Acta Cryst. 17, 1613.]). A chemical analysis of the analysed crystal was not performed because of its very small size. As is typical for minerals from volcanic fumaroles, the mineral is fine grained and intimately mixed with several other phases, which makes an accurate chemical analysis extremely difficult, even on a larger sample. The correspondence of the current crystal-structure parameters to those of the synthetic compound and the results of structural refinement indicate that the chemical composition is indeed very close to ideal without apparent influence from chemical impurities.

Table 2
Experimental details

Crystal data
Chemical formula Na6Mg(SO4)4
Mr 546.5
Crystal system, space group Monoclinic, P21/c
Temperature (K) 296
a, b, c (Å) 9.7761 (6), 9.1998 (4), 8.2040 (5)
β (°) 113.518 (7)
V3) 676.56 (7)
Z 2
Radiation type Mo Kα
μ (mm−1) 1.04
Crystal size (mm) 0.03 × 0.02 × 0.004
 
Data collection
Diffractometer SuperNova Rigaku Oxford Diffraction diffractometer with Pilatus200K detector
Absorption correction Multi-scan (CrysAlis PRO; Rigaku OD, 2019[Rigaku OD (2019). CrysAlis PRO. Rigaku Oxford Diffraction, Yarnton, England.])
Tmin, Tmax 0.860, 1.000
No. of measured, independent and observed [I > 3σ(I)] reflections 18695, 2211, 1432
Rint 0.087
(sin θ/λ)max−1) 0.744
 
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.032, 0.037, 1.29
No. of reflections 2211
No. of parameters 124
Δρmax, Δρmin (e Å−3) 0.61, −0.67
Computer programs: CrysAlis PRO (Rigaku OD, 2019[Rigaku OD (2019). CrysAlis PRO. Rigaku Oxford Diffraction, Yarnton, England.]), SUPERFLIP (Oszlányi & Sütő, 2004[Oszlányi, G. & Sütő, A. (2004). Acta Cryst. A60, 134-141.]; Palatinus & Chapuis, 2007[Palatinus, L. & Chapuis, G. (2007). J. Appl. Cryst. 40, 786-790.]), JANA2006 (Petříček et al., 2014[Petříček, V., Dušek, M. & Palatinus, L. (2014). Z. Kristallogr. 229, 345-352.]), ATOMS (Dowty, 2005[Dowty, E. (2005). ATOMS. Shape Software, Kingsport, Tennessee, USA.]).

Supporting information


Computing details top

Data collection: CrysAlis PRO (Rigaku OD, 2019); cell refinement: CrysAlis PRO (Rigaku OD, 2019); data reduction: CrysAlis PRO (Rigaku OD, 2019); program(s) used to solve structure: Superflip (Oszlányi & Sütő, 2004; Palatinus & Chapuis, 2007); program(s) used to refine structure: Jana2006 (Petříček et al., 2014); molecular graphics: ATOMS (Dowty, 2005).

Hexasodium magnesium tetrakis[sulfate(VI)] top
Crystal data top
Na6Mg(SO4)4F(000) = 540
Mr = 546.5Dx = 2.682 Mg m3
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ycbCell parameters from 3897 reflections
a = 9.7761 (6) Åθ = 2.3–31.7°
b = 9.1998 (4) ŵ = 1.04 mm1
c = 8.2040 (5) ÅT = 296 K
β = 113.518 (7)°Plate, colourless
V = 676.56 (7) Å30.03 × 0.02 × 0.004 mm
Z = 2
Data collection top
SuperNova Rigaku Oxford Diffraction
diffractometer with Pilatus200K detector
2211 independent reflections
Radiation source: micro-focus sealed X-ray tube, SuperNova (Mo) X-ray Source1432 reflections with I > 3σ(I)
Mirror monochromatorRint = 0.087
Detector resolution: 5.8140 pixels mm-1θmax = 31.9°, θmin = 2.3°
ω scansh = 1414
Absorption correction: multi-scan
(CrysAlisPro; Rigaku OD, 2019)
k = 1313
Tmin = 0.860, Tmax = 1.000l = 1211
18695 measured reflections
Refinement top
Refinement on F0 restraints
R[F2 > 2σ(F2)] = 0.0320 constraints
wR(F2) = 0.037Weighting scheme based on measured s.u.'s w = 1/(σ2(F) + 0.0001F2)
S = 1.29(Δ/σ)max = 0.047
2211 reflectionsΔρmax = 0.61 e Å3
124 parametersΔρmin = 0.67 e Å3
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
S10.14002 (6)0.30539 (6)0.22425 (8)0.01023 (19)
S20.66143 (6)0.35283 (6)0.34685 (8)0.01116 (19)
Mg10000.0097 (4)
Na10.31120 (11)0.01426 (11)0.46772 (12)0.0173 (4)
Na20.44443 (12)0.15141 (12)0.09037 (14)0.0262 (4)
Na30.88822 (12)0.13860 (11)0.31627 (14)0.0231 (4)
O10.03029 (18)0.18470 (18)0.1553 (2)0.0153 (6)
O20.13531 (19)0.39708 (19)0.0752 (2)0.0169 (6)
O30.0954 (2)0.39427 (19)0.3441 (2)0.0197 (7)
O40.28894 (18)0.24382 (19)0.3187 (2)0.0198 (7)
O50.66765 (19)0.19352 (18)0.3593 (2)0.0175 (6)
O60.6464 (2)0.4160 (2)0.5023 (2)0.0208 (7)
O70.80007 (17)0.40614 (19)0.3324 (2)0.0154 (6)
O80.53693 (18)0.39792 (19)0.1825 (2)0.0190 (6)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
S10.0103 (3)0.0099 (3)0.0103 (3)0.0010 (2)0.0039 (2)0.0008 (2)
S20.0109 (3)0.0099 (3)0.0126 (3)0.0001 (2)0.0046 (2)0.0006 (2)
Mg10.0096 (5)0.0090 (6)0.0101 (5)0.0002 (4)0.0034 (4)0.0002 (4)
Na10.0195 (5)0.0154 (5)0.0181 (5)0.0002 (4)0.0088 (4)0.0005 (4)
Na20.0266 (6)0.0187 (6)0.0259 (6)0.0064 (4)0.0026 (5)0.0002 (5)
Na30.0257 (6)0.0206 (6)0.0305 (6)0.0040 (4)0.0190 (5)0.0039 (5)
O10.0156 (8)0.0149 (9)0.0167 (9)0.0076 (7)0.0077 (7)0.0072 (7)
O20.0222 (9)0.0155 (9)0.0159 (9)0.0009 (7)0.0105 (7)0.0041 (7)
O30.0267 (10)0.0184 (10)0.0189 (10)0.0037 (8)0.0145 (8)0.0073 (8)
O40.0118 (8)0.0182 (10)0.0251 (10)0.0011 (7)0.0028 (7)0.0031 (8)
O50.0223 (9)0.0111 (9)0.0195 (9)0.0010 (7)0.0088 (7)0.0027 (7)
O60.0270 (10)0.0198 (10)0.0219 (10)0.0028 (8)0.0165 (8)0.0052 (8)
O70.0095 (8)0.0208 (9)0.0144 (9)0.0026 (7)0.0031 (7)0.0005 (7)
O80.0113 (8)0.0231 (10)0.0174 (9)0.0007 (7)0.0003 (7)0.0061 (8)
Geometric parameters (Å, º) top
S1—O11.4897 (17)Na1—O8i2.516 (2)
S1—O21.4710 (19)Na1—O8vii2.3504 (17)
S1—O31.472 (2)Na1—O42.406 (2)
S1—O41.4630 (16)Na3—O72.628 (2)
S2—O71.490 (2)Na3—O1viii2.305 (2)
S2—O51.4687 (18)Na3—O52.374 (2)
S2—O81.4703 (15)Na3—O2i2.438 (2)
S2—O61.461 (2)Na3—O2ix2.5219 (18)
Mg1—O7i2.0765 (15)Na3—O3i2.641 (2)
Mg1—O7ii2.0765 (15)Na3—O6v2.7595 (18)
Mg1—O12.0732 (17)Na2—O52.4368 (18)
Mg1—O1iii2.0732 (17)Na2—O82.447 (2)
Mg1—O3iv2.099 (2)Na2—O8i2.945 (2)
Mg1—O3v2.099 (2)Na2—O42.969 (3)
Na1—O7i2.4691 (19)Na2—O4v2.3460 (19)
Na1—O5vi2.340 (2)Na2—O6i2.349 (2)
Na1—O2vii2.369 (2)Na2—O6v2.438 (3)
O1—S1—O2109.45 (9)O7—Na3—O1viii98.11 (7)
O1—S1—O3107.87 (11)O7—Na3—O557.17 (6)
O1—S1—O4109.04 (10)O7—Na3—O2i138.97 (9)
O2—S1—O3108.49 (11)O7—Na3—O2ix107.61 (6)
O2—S1—O4110.90 (12)O7—Na3—O3i155.25 (6)
O3—S1—O4111.03 (10)O7—Na3—O6v92.37 (6)
O7—S2—O5108.68 (11)O1viii—Na3—O5146.76 (7)
O7—S2—O8106.29 (11)O1viii—Na3—O2i122.88 (8)
O7—S2—O6110.50 (11)O1viii—Na3—O2ix85.01 (7)
O5—S2—O8109.97 (9)O1viii—Na3—O3i72.61 (7)
O5—S2—O6110.59 (11)O1viii—Na3—O6v89.22 (7)
O8—S2—O6110.70 (11)O5—Na3—O2i85.18 (7)
O7i—Mg1—O7ii180O5—Na3—O2ix121.59 (8)
O7i—Mg1—O193.89 (6)O5—Na3—O3i119.63 (7)
O7i—Mg1—O1iii86.11 (6)O5—Na3—O6v71.75 (7)
O7i—Mg1—O3iv86.17 (7)O2i—Na3—O2ix76.82 (6)
O7i—Mg1—O3v93.83 (7)O2i—Na3—O3i55.92 (7)
O7ii—Mg1—O186.11 (6)O2i—Na3—O6v90.26 (6)
O7ii—Mg1—O1iii93.89 (6)O2ix—Na3—O3i94.63 (6)
O7ii—Mg1—O3iv93.83 (7)O2ix—Na3—O6v159.78 (7)
O7ii—Mg1—O3v86.17 (7)O3i—Na3—O6v65.16 (6)
O1—Mg1—O1iii180O5—Na2—O859.06 (6)
O1—Mg1—O3iv89.68 (7)O5—Na2—O8i75.29 (6)
O1—Mg1—O3v90.32 (7)O5—Na2—O483.23 (7)
O1iii—Mg1—O3iv90.32 (7)O5—Na2—O4v143.28 (8)
O1iii—Mg1—O3v89.68 (7)O5—Na2—O6i121.73 (7)
O3iv—Mg1—O3v180O5—Na2—O6v76.71 (7)
O7i—Na1—O5vi99.95 (7)O8—Na2—O8i128.07 (7)
O7i—Na1—O2vii114.43 (7)O8—Na2—O476.04 (7)
O7i—Na1—O8i56.73 (6)O8—Na2—O4v86.11 (6)
O7i—Na1—O8vii142.59 (9)O8—Na2—O6i179.16 (7)
O7i—Na1—O486.12 (7)O8—Na2—O6v94.82 (8)
O5vi—Na1—O2vii87.54 (8)O8i—Na2—O475.26 (6)
O5vi—Na1—O8i91.31 (7)O8i—Na2—O4v141.22 (7)
O5vi—Na1—O8vii89.82 (6)O8i—Na2—O6i52.75 (6)
O5vi—Na1—O4173.33 (8)O8i—Na2—O6v97.65 (7)
O2vii—Na1—O8i170.73 (6)O4—Na2—O4v100.43 (7)
O2vii—Na1—O8vii101.91 (7)O4—Na2—O6i104.22 (8)
O2vii—Na1—O487.42 (7)O4—Na2—O6v159.86 (6)
O8i—Na1—O8vii87.27 (7)O4v—Na2—O6i93.06 (7)
O8i—Na1—O494.35 (8)O4v—Na2—O6v96.74 (8)
O8vii—Na1—O486.94 (6)O6i—Na2—O6v85.18 (8)
Symmetry codes: (i) x+1, y1/2, z+1/2; (ii) x1, y+1/2, z1/2; (iii) x, y, z; (iv) x, y1/2, z+1/2; (v) x, y+1/2, z1/2; (vi) x+1, y, z+1; (vii) x, y+1/2, z+1/2; (viii) x+1, y, z; (ix) x+1, y+1/2, z+1/2.
The parameters of the coordination polyhedra calculated with the program IVTON (Balić-Žunić &amp; Vicković, 1996) top
CationCN<d> (Å)bvsVp (Å3)vdaspecc
S141.4746.0021.643 (4)0.000300.0115
S241.4736.0271.637 (4)0.000600.0124
Mg62.0832.09411.99 (2)0.00460.00600
Na162.4081.17717.18 (2)0.07160.01190.0392
Na272.5611.07424.64 (4)0.06740.05860.0480
Na372.5241.07122.76 (3)0.09570.06020.1492
Notes: CN = coordination number; <d> = average bond length; bvs = bond valence sum, calculated using the exponential function of Brown & Altermatt (1985) with the parameters of Breese & O'Keeffe (1991); Vp = polyhedral volume; vd = volume distortion; asp = asphericity; ecc = eccentricity.
 

Acknowledgements

We are indebted to the Icelandic Institute of Natural History and the late Dr Svein Peter Jakobsson for providing us with the sample containing vanthoffite crystals.

References

First citationBalić-Žunić, T., Garavelli, A., Jakobsson, S. P., Jonasson, K., Katerinopoulos, A., Kyriakopoulos, K. & Acquafredda, P. (2016). In: Updates in Volcanology – From Volcano Modelling to Volcano Geology, edited by K. Nemeth. London: InTechOpen. DOI: 10.5772/64129.  Google Scholar
First citationBalić Žunić, T. & Makovicky, E. (1996). Acta Cryst. B52, 78–81.  CrossRef Web of Science IUCr Journals Google Scholar
First citationBalić Žunić, T. & Vicković, I. (1996). J. Appl. Cryst. 29, 305–306.  CrossRef IUCr Journals Google Scholar
First citationBrese, N. E. & O'Keeffe, M. (1991). Acta Cryst. B47, 192–197.  CrossRef CAS Web of Science IUCr Journals Google Scholar
First citationBrown, I. D. & Altermatt, D. (1985). Acta Cryst. B41, 244–247.  CrossRef CAS Web of Science IUCr Journals Google Scholar
First citationDowty, E. (2005). ATOMS. Shape Software, Kingsport, Tennessee, USA.  Google Scholar
First citationEdenharter, A. (1976). Schweiz. Miner. Petro. Mitt. 56, 195–217.  CAS Google Scholar
First citationFischer, W. (1973). Z. Kristallogr. 137, 445–446.  Google Scholar
First citationFischer, W. & Hellner, E. (1964). Acta Cryst. 17, 1613.  CrossRef ICSD IUCr Journals Web of Science Google Scholar
First citationHawthorne, F. C., Krivovichev, S. V. & Burns, P. C. (2000). Rev. Mineral. Geochem. 40, 1–112.  Web of Science CrossRef CAS Google Scholar
First citationMakovicky, E. & Balić-Žunić, T. (1998). Acta Cryst. B54, 766–773.  Web of Science CrossRef IUCr Journals Google Scholar
First citationMoore, P. B. (1973). Am. Mineral. 58, 32–42.  CAS Google Scholar
First citationOszlányi, G. & Sütő, A. (2004). Acta Cryst. A60, 134–141.  Web of Science CrossRef IUCr Journals Google Scholar
First citationPalatinus, L. & Chapuis, G. (2007). J. Appl. Cryst. 40, 786–790.  Web of Science CrossRef CAS IUCr Journals Google Scholar
First citationPekov, I. V., Zubkova, N. V., Yapaskurt, V. O., Britvin, S. N., Vigasina, M. F., Sidorov, E. G. & Pushcharovsky, D. Y. (2015). Eur. J. Mineral. 27, 581–588.  Web of Science CrossRef ICSD CAS Google Scholar
First citationPetříček, V., Dušek, M. & Palatinus, L. (2014). Z. Kristallogr. 229, 345–352.  Google Scholar
First citationRigaku OD (2019). CrysAlis PRO. Rigaku Oxford Diffraction, Yarnton, England.  Google Scholar
First citationSharma, V., Swain, D. & Guru Row, T. N. (2017). Inorg. Chem. 56, 6048–6051.  Web of Science CrossRef ICSD CAS PubMed Google Scholar

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