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Disodium hexa­manganese(II,III) germanate is the first aenigmatite-type compound with significant amounts of manganese. Na2(Mn5.26Na0.74)Ge6O20 is triclinic and contains two different Na positions, six Ge positions and 20 O positions (all with site symmetry 1 on general position 2i of space group P\overline{1}). Five out of the seven M positions are also on general position 2i, while the remaining two have site symmetry \overline{1} (Wyckoff positions 1f and 1c). The structure can be described in terms of two different layers, A and B, stacked along the [011] direction. Layer A contains pyroxene-like chains and isolated octa­hedra, while layer B is built up by slabs of edge-sharing octa­hedra connected to one another by bands of Na polyhedra. The GeO4 tetra­hedra show slight polyhedral distortion and are among the most regular found so far in germanate compounds. The M sites of layer A are occupied by highly charged (trivalent) cations, while in layer B a central pyroxene-like zigzag chain can be identified, which contains divalent (or low-charged) cations. This applies to the aenigmatite-type compounds in general and to the title compound in particular.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270107068011/iz3033sup1.cif
Contains datablocks global, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270107068011/iz3033Isup2.hkl
Contains datablock I

Comment top

Synthesis and crystal chemical investigations in the system of 1:3 Na and Li transition-metal germanate pyroxenes have shown that at ambient pressures pyroxene phases NaM3+Ge2O6 (M = Cr, Fe, Sc and In) and LiM3+Ge2O6 (M = Al, Ga, Cr, Fe, Sc and In) can be grown as high-quality single crystals using high-temperature solution (flux) techniques (Redhammer et al., 2008). To extend the range of M-cationic substitution in clinopyroxene, the crystallization of Mn3+-bearing Na germanate pyroxenes was attempted, but it was found that the pyroxene structure is not stable; instead, crystals of a new aenigmatite-type phase have been formed, whose crystal structure is described here.

The triclinic aenigmatite group of compounds can be summarized with the general formula A2B6T6O20, where A = Na or Ca in six- to eightfold coordination, B is octahedrally coordinated Fe2+, Fe3+, Mg, Al, Cr, Ti4+ or Sb5+, and C is tetrahedrally coordinated Si, Al, B or Be. The mineral group comprises several naturally occurring minerals, such as aenigmatite itself, Na2Fe5TiSi6O20 (Cannillo et al., 1971), wilkinsonite, Na2Fe2+4Fe3+2Si6O20 (Burt et al., 2007), krinovite, Na2Mg4Cr2Si6O20 (Merlino, 1972; Bonaccorsi et al., 1989), rhönite, Ca2(Mg,Fe,Ti)6Si6O20 (Bonaccorsi et al., 1990), or sapphirine-1Tc, (MgAl)8Si6O20 (Merlino, 1980); a detailed review of the aenigmatite group is given by Kunzman or Kunzmann (1999). Additionally the crystal structures of several Be-containing minerals, closely related to the aenigmatite group, have been refined recently, among them surinamite, (Mg, Fe2+)3Al4BeSi3O16, makarochinite, Ca2Fe2+4Fe3+TiSi6O20 (Grew et al., 2005), and welshite, Ca2Mg4Fe3+Sb5+Si4Be2O20 (Grew et al., 2007). Besides the naturally occurring species, Barbier (1995) reported the synthetic aenigmatite analog germanate, Na2(Mg,Fe)6(Ge,Fe)6O18O2, while Yang & Konzett (2000) describe Na2Mg6Si6O18(OH)2 and Gasparik et al. (1999) report Na2(Mg4.31Si0.39Fe1.3)Si6O20. The title compound is of special interest as it is the first aenigmatite-type material containing Mn as the dominant octahedral cation.

The structure of Na2(Mn5.26Na0.74)Ge6O20 contains six distinct octahedrally coordinated M (M = Mn and Na) sites, two different sevenfold-coordinated Na sites, six distinct Ge sites and 20 O-atom positions. An anisotropic displacement plot, containing the atomic nomenclature, is given in Fig. 1. The structural topology is described in terms of two layers stacked alternately along the [011] direction (Fig. 2). The first layer, labelled layer A from here on, contains pyroxene-like chains (Ge1–Ge4) extending in the [100] direction with two additional corner-sharing GeO4 tetrahedra attached laterally (Fig. 3a). Within this layer, the tetrahedral chains are connected by isolated octahedra (Mn1 and Mn2). The second layer (layer B) is formed by infinite slabs of edge-sharing octahedra extending along a (M3–M7). These slabs are linked by `bands' of Na polyhedra (Fig. 3b).

The average Ge—O bond lengths within the tetrahedral chain of layer A are similar (~ 1.741–1.747 Å), except for the Ge3 site, where the average is somewhat smaller (Table 1). This is due to a very small Ge3—O8 bond length [1.699 (5) Å]. Atom O8 is common to the Ge3, the M5 and two M6 polyhedra. The M6 sites, hosting Na+ cations, exhibit a low valence sum (Brese & O'Keeffe, 1991) of 1.47 valence units (v.u.) and are only weakly bound to atom O8; they contribute 0.34 and 0.22 v.u to the valence sum of atom O8. Thus the remaining two bonds of O8 to Ge3 and M5 are expected to be stronger and thus shorter. The Ge1 and Ge4 tetrahedra have two Ge—O bridging bonds, the Ge—Obr distance being typically longer than the non-bridging Ge—Onbr distances. This is most evident for the Ge1 tetrahedron, with two short [ Ge—Onbr = 1.723 (5) Å] and two long [ Ge—Obr] = 1.772 (5) Å] bonds. The Ge2 and Ge3 tetrahedra have three bridging bonds with neighboring tetrahedra, with Ge—Obr distances of 1.753 (5) and 1.744 (5) Å, respectively; the difference Δbr = Ge—Obr - Ge—Onbr is 0.047 and 0.045 Å for Ge2 and Ge3, respectively.

Synthetic Na2(Mg3.6Fe2.4)[(Ge5.6Fe0.4)O18]O2 shows a more uniform distribution of individual Ge—O bond lengths, ranging between 1.722 (2) and 1.781 (2) Å (Barbier, 1995). The Ge—Obr values are comparable to those in the title compound; however, the Δbr values are approximately half of the value found here, i.e. the bond-length distortion (Renner & Lehmann, 1986) is smaller for the title compound (Table 1). The Ge3 tetrahedron [eqiuivalent to T4 in Barbier (1995)] is much more regular and does not display a short Ge—O bond pointing towards the M-site layer as found in the title compound. However, the trioctahedral unit of Mn6–Mn6i–Mn5 sites, to which atom O8 is bonded besides Ge3ii [symmetry codes: (i) 1 - x, 2 - y, -z; (ii) x, y, -1 + z], exhibits a less uniform charge distribution in Na2(Mn5.26Na0.74)Ge6O20 than in the Barbier (1995) sample Na2(Mg3.6Fe2.4)[(Ge5.6Fe0.4)O18]O2. Here M6 is exclusively occupied by Mg2+ and M5 has an Mg0.742+Fe0.263+ composition, while the title compound has – on the basis of bond valence calculations (Brese & O'Keeffe, 1991) – an Na0.74+Mn0.262+ and Mn0.322+Mn0.683+ composition for M6 and M5, respectively.

Generally, the GeO4 tetrahedra are remarkably regular in the title compound. Both the tetrahedral angle variance (TAV) and the tetrahedral quadratic elongation (TQE) parameters (Robinson et al., 1971) are low, the Ge5 and Ge6 tetrahedra being somewhat more regular than those within the tetrahedral chain. For comparison, distortion parameters found in other germanates are most frequently found in the ranges between 40 and 100° for TAV, and 1.01 and 1.02 for TQE (Redhammer & Roth 2004, 2006; Redhammer et al., 2005, 2006, 2007a,b,c; Redhammer, Merz et al., 2007). The most regular GeO4 tetrahedra found so far are realised in Cu2Fe2Ge4O13 (the Ge3 site with TAV and TQE values of 1.6° and 1.0005; Redhammer, Merz et al., 2007) and in Cu(Cu0.44Cr4.58)Ge2O12 (with TAV and TQE values of 5.32° and 1.0013, respectively; Redhammer et al., 2007a). The bond valence sums of the Ge sites in the title compound are close to the expected value, the GeO4 tetrahedra within the chain being slightly overbonded, while the `attached' ones are somewhat underbonded.

The chain of Ge1–Ge4 tetrahedra is distinctly kinked in Na2(Mn5.26Na0.74)Ge6O20; the average O—O—O tetrahedral bridging angle is 146.4 (1)°, with the individual values ranging between 140.9 and 152.1° (Table 1). A similar average kinking angle of 143.3° was found by Barbier (1995) for the Na–Mg–Fe germanate. These O—O—O angles compare well with the tetrahedral bridging angle in germanate clinopyroxenes, e.g. in synthetic LiFeGe2O6 [137.6 (1) and 151.1 (1)° for the A and B chain in the P21/c phase at 298 K; Redhammer et al., 2008] or in CaCuGe2O6 [with the A and B chains kinked by 139.3 (1)° and 179.9 (1)° in the P21/c phase at ~720 K, while the bridging angle is 159.4 (1)° in the C2/c phase at ~800 K (Redhammer et al., 2005)]. The aenigmatite-type silicate minerals show bridging angles that are larger by ~10–12°. Average T—O bond lengths in aenigmatite-type compounds are positively correlated with the average tetrahedral radius of the individual T sites (Table 1); however, no systematic variation is found for any polyhedral distortion parameter. This indicates that the distortional geometry of the tetrahedra is dominated by the geometry of the neighboring polyhedra, especially by the M-site cations and by the way in which O atoms are shared between neighbouring sites.

The M1 and M2 octahedra connect individual chains of GeO4 tetrahedra with each other along the c direction. Thereby, the apices of the tetrahedra alternate `up' and `down' (Figs. 2 and 3a). The isolated M1 and M2 sites are characterized by a small M—O bond length and are preferently filled by trivalent or highly charged cations in the aenigmatite-type compounds. In krinovite, Na2Mg4Cr2Si6O20, these two sites exclusively host Cr3+ (Bonaccorsi et al., 1989), while in rhönite, Ca2(Mg, Fe, Ti)6Si6O20, M1 and M2 are characterized by high amounts of Ti4+ (Bonaccorsi et al., 1990). On the basis of bond-valence considerations, Burt et al. (2007) state that M1 and M2 are filled by 84 and 70% Fe3+ in wilkinsonite, Na2Fe6Si6O20. Finally, Fe3+ clearly dominates Mg2+ in Na2(MgFe)[(GeFe)O18]O2, having an occupation of 80% in M1 and M2. In most of the aenigmatite-type compounds, the average M1—O and M2—O distances are – together with M7—O – the smallest of all M—O bond lengths. This is also true for the title compound. On the basis of bond-valence calculations, the small M1—O and M2—O values of 2.037 (6) and 2.047 (5) Å indicate that Mn is almost exclusively in the trivalent state on these two sites. The M1 and M2 polyhedra connect the tetrahedral `A' layer with two neighboring `B' layers, by sharing four of their edges with the M5 and M7 octahedra (two edges each for the layer above and below the `A' layer). In comparison to other aenigmatite-type compounds, it is evident that Mn3+ with its 3d4 electronic configuration causes a distinct distortion to the M1 and M2 sites, expressed by a large BLD value but also by large octahedral angle variance and quadratic octahedral elongation parameters (Table 1). In the silicate aenigmatite-type minerals these two polyhedra appear to be much more regular (Table 1); the Na—Mg—Fe germanate of Barbier (1995) also exhibits less polyhedral distortion.

The slab of M sites, which is the main building unit of the `B' layer in the aenigmatite structure (Figs. 2 and 3b), hosts the M3–M7 octahedra. The average M—O bond lengths range between 2.054 (5) and 2.321 (5) Å, reflecting the mixed occupation with Mn2+, Mn3+ and Na+. All three cations rarely occupy the M sites in aenigmatite-type compounds known so far. Thus the M—O bond lengths in the title compound are amongst the largest reported. Using bond-valence analysis (Brese & O'Keeffe, 1991), Mn2+/Mn3+ ratios on the different M sites have been determined in a manner similar to that described by Burt et al. (2007), giving Mn3+ percentages of, respectively, 38% on M3, 0% on M4, 32% on M5, 0% on M6 and 79% on M7; M1 and M2 are occupied by 100% Mn3+, while for M6 the site occupancy is given as Na0.74Mn2+0.26. Using these Mn2+/Mn3+ ratios to calculate average cationic radii rM, a well defined positive correlation is valid between M—O and rM. This trend is well met by data from several other enigmatite-type compounds (Fig. 4). All `B'-layer octahedra are connected to each other by corner sharing. Along the a direction, a four-octahedra unit, consisting of two M3 and two M4 octahedra, alternates with a six-octahedra unit of two M5, two M6 and two M7 octahedra. The M6 polyhedron thereby is the only one that shares six of its edges with neighboring M polyhedra and shows – by far – the largest average M—O bond length. This is due to the presence of Na+ at M6, a feature not reported so far for the aenigmatite structure type, but also due to the intense edge sharing with the neighboring sites. Among all M sites, the M6 octahedron is the most distorted; the value found for the title compound thereby is the largest reported so far for aenigmatite-type compounds. Generally the M6 site deviates most from ideal octahedral geometry in the aenigmatite structure (Table 1). A rough positive correlation can be found between average cationic radius rM and polyhedral distortion parameters, e.g. between rM and OAV for some M sites; this is most evident for the M3 and M5 sites, while the polyhedral distortion of the M1, M2 and M7 octahedra appears to be independent of rM and is dominated by geometric constraints from their neighboring sites. The M4 site displays the second largest M—O bond length, reflecting – corroborated by the bond valence sum – that this site is occupied by Mn2+ exclusively. It is this site which is the most regular in terms of bond length and angular distortion (Table 1). This can be regarded as additional evidence that M4 is occupied only by Mn2+ with its closed-shell 3d5 electronic configuration. In most aenigmatite-type compounds, except rhönite, the M4 site is occupied by divalent cations only. In contrast, the M7 site, sharing a common edge with the M1 site of the `A' layer, preferentally accomodates highly charged cations, e.g. Fe3+ only in synthetic Na2(Mg,Fe)6(Ge,Fe)6O18O2 (Barbier 1995), or Cr3+ in krinovite. From this charge distribution, it is evident that, within the `B'-layer M3–M7 octahedral slab, a central pyroxene-like zigzag chain of edge-sharing M4–M4–M6–M6–M4··· octahedra can be identified which preferentally contains divalent cations, or more generally, cations with low charge, while the M3, M5 and M7 octahedra, attached to this chain, host – additionally or exclusively – trivalent or higher valent cations. This zigzag chain, which is closely related to the M1 chain of the clinopyroxene structure, reveals the very same interconnection with the chain of Ge1–Ge4 tetrahedra as is realised in the clinopyroxenes (Fig. 3b). Thus an alternative description of the aenigmatite-type structure addresses pyroxene-like slabs, which alternate with spinel-like slabs (Barbier, 1995; Yang & Konzett, 2000).

A major difference between the title compound and other aenigmatite-type compounds lies in the coordination geometry of the Na+ (A) cation. In the title compound, Na exhibits a (6 + 1)-fold coordination for both A sites, with six Na—O bonds between 2.346 (6) and 2.553 (6) Å, the seventh being 2.805 (6) and 2.793 (6) Å apart. The next nearest O atoms to Na1 and Na2 are 3.249 (s.u.?) and 3.234 (s.u.?) Å away and are regarded as nonbonding. A similar observation was made by Barbier (1995) for the synthetic NaMg germanate. These longest coordinating A—O bond lengths are distinctly shorter in the germanate compounds than in the silicate aenigmatites of Table 1, where the longest A—O bonds range between 2.95 and 3.06 Å. Barbier (1995) states that this (6 + 1)-fold coordination of the Na sites is intermediate between the (7 + 1)-fold coordination as found in, for example, aenigmatite (Cannillo et al., 1971) and the sapphirine structure with the corresponding sixfold coordinated Mg-rich sites (Barbier, 1995). The coordination of the A-site cations is directly related to the conformation state of the pyroxene-like tetrahedral chains. Silicate aegimatite minerals with their (7 + 1) coordination have average tetrahedal kinking angles above 150°, in the synthetic germanates the average kinking angles are 143.3 and 146.3°, while sappirine with the sixfold-coordinated Mg sites shows small tetrahedral kinking angles of 130.3° only. A well defined negative correlation is valid between the conformation state of the tetrahedral chain and the long distant A—O bonds, i.e. the more the tetrahedral chains are stretched, the closer the long distant O atoms are moved towards the A cations; in anigmatite and wilkinsonite with the largest O—O—O angles, the eighth O atoms in the coordination polyhedron are ~ 2.95 Å apart and have to be regarded as bonding O atoms leading to the (7 + 1)-fold coordination (Table 1). In the clinopyroxenes, the principal mechanism is similar but reversed: As the tetrahedral chain becomes stretched, the respective O atom corresponding to the largest distance moves out of the coordination environment of the M2 sites, most instructively displayed by the low-temperature behaviour upon the C2/cP21/c phase transitions in Li clinopyroxenes (Redhammer et al., 2002, 2004).

Related literature top

For related literature, see: Barbier (1995); Bonaccorsi et al. (1989, 1990); Brese & O'Keeffe (1991); Burt et al. (2007); Cannillo et al. (1971); Gasparik et al. (1999); Grew et al. (2005, 2007); Merlino (1972, 1980); Redhammer & Roth (2004, 2006); Redhammer et al. (2005); Renner & Lehmann (1986); Robinson et al. (1971); Sheldrick (1997); Yang & Konzett (2000).

Experimental top

As part of our crystal chemical investigations of (Na,Li)MGe2O6 1:3 germanate clinopyroxene compounds (Redhammer et al., 2008), the title compound was obtained accidentaly during attempts to synthesize NaMnGe2O6 using flux growth methods. A finely ground and homogenized mixture of Na2CO3, Mn2O3 and GeO2 in the stoichiometry of NaMnGe2O6 was added to the high-temperature solvent (80 wt% Li2MoO4 and 20 wt% LiVO3) in a ratio of educt to flux of 1 g:10 g. This staring material was put into a platinum crucible, covered with a lid and heated in a chamber furnace to 1473 K, held for 24 h at this temperature, and cooled to 973 K at a rate of 1.8 K h-1. After dissolution of the flux in hot distilled water, dark-brown-to-black needle-like crystals were obtained. Chemical analysis was performed on three different grains using an electron microprobe, yielding 7.60% Na2O, 33.62% MnO and 56.42 GeO2 by weight; no other elements are present in the sample, as proven by energy dispersive X-ray analysis. On the basis of 20 O atoms and the Mn2+/Mn3+ ratio extracted from bond-valence calculations, this gives rise to the structural fomula Na2.73 (2)Mn5.28 (1)Ge6.01 (2)O20, which is identical to the formula derived from structure refinement within experimental error.

Refinement top

Structure solution using Patterson methods (Sheldrick, 1997) yielded the Ge and the Mn positions; O atoms and Na atoms were localized from difference Fourier map analysis. After full anisotropic refinement against F2 with all the M sites filled with Mn, it became evident that the Mn6 site is partly empty or partly substituted. Allowing the site occupation factor of Mn6 to refine freely yielded an occupation of 0.43 Mn, signifcantly below the expected value of 1, and a drop of the R1 value by nearly 4%. As chemical analysis showed an Na content above the expected 2.0 formula units, a mixed occupation of M6 with Mn + Na was tested. The refinement converged to an occupation very close to that expected from chemical analysis.

Computing details top

Data collection: SMART-Plus (Bruker, 2001); cell refinement: SAINT-Plus (Bruker, 2001); data reduction: SAINT-Plus (Bruker, 2001); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Version 3.0; Pennington, 1999); software used to prepare material for publication: WinGX (Version 1.70.01; Farrugia, 1999).

Figures top
[Figure 1] Fig. 1. A view of the asymmetric unit and some symmetry-related atoms of the title compound, showing 95% probability displacement ellipsoids and the atomic numbering scheme. [Symmetry codes: (i) x + 1, y, z; (ii) -x, -y + 1, -z + 2; (iii) -x + 1, -y + 1, -z + 1; (iv) -x + 1, -y + 1, -z + 2; (v) x, y, z + 1; (vi) -x + 1, -y + 2, -z + 1; (vii) -x, -y + 1, -z + 1; (viii) x + 1, y, z - 1; (ix) x, y, z - 1; (x) -x, -y + 2, -z + 1.] [vii is not actually used in figure; can it be omitted?]
[Figure 2] Fig. 2. A polyhedral representation of the aenigmatite-type structure, viewed down the [100] direction, displaying the structure of stacked A and B layers.
[Figure 3] Fig. 3. : A polyhedral representation of the aenigmatite-type structure, viewed down the [111] direction, depicting (a) the Ge1—Ge6 `A' layer and (b) the slabs of the M-site `B' layers.
[Figure 4] Fig. 4. : Correlation between average ionic radius rM and M—O for the different M sites in different aenigmatite-type compounds.
Disodium hexamanganese(II,III) germanate top
Crystal data top
Na2(Mn5.26Na0.74)Ge6O20Z = 2
Mr = 1107.49F(000) = 1027.4
Triclinic, P1Dx = 4.565 Mg m3
a = 10.5578 (9) ÅMo Kα radiation, λ = 0.71073 Å
b = 11.1532 (7) ÅCell parameters from 8361 reflections
c = 9.1833 (7) Åθ = 3.4–27.7°
α = 106.707 (2)°µ = 15.17 mm1
β = 95.809 (1)°T = 295 K
γ = 124.367 (5)°Prism, black
V = 806.05 (11) Å30.09 × 0.07 × 0.04 mm
Data collection top
Bruker SMART APEX
diffractometer
2545 reflections with I > 2σ(I)
rotation, ω–scans at 4 different ϕ positionsRint = 0.073
Absorption correction: numerical
via equivalents using X-SHAPE (Stoe & Cie, 1996)
θmax = 26.7°, θmin = 2.1°
Tmin = 0.29, Tmax = 0.55h = 1313
9401 measured reflectionsk = 1414
3400 independent reflectionsl = 1111
Refinement top
Refinement on F21 restraint
Least-squares matrix: full w = 1/[σ2(Fo2) + (0.0165P)2]
where P = (Fo2 + 2Fc2)/3
R[F2 > 2σ(F2)] = 0.042(Δ/σ)max < 0.001
wR(F2) = 0.082Δρmax = 1.22 e Å3
S = 0.95Δρmin = 1.04 e Å3
3400 reflectionsExtinction correction: SHELXL97, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
313 parametersExtinction coefficient: 0.00264 (19)
Crystal data top
Na2(Mn5.26Na0.74)Ge6O20γ = 124.367 (5)°
Mr = 1107.49V = 806.05 (11) Å3
Triclinic, P1Z = 2
a = 10.5578 (9) ÅMo Kα radiation
b = 11.1532 (7) ŵ = 15.17 mm1
c = 9.1833 (7) ÅT = 295 K
α = 106.707 (2)°0.09 × 0.07 × 0.04 mm
β = 95.809 (1)°
Data collection top
Bruker SMART APEX
diffractometer
3400 independent reflections
Absorption correction: numerical
via equivalents using X-SHAPE (Stoe & Cie, 1996)
2545 reflections with I > 2σ(I)
Tmin = 0.29, Tmax = 0.55Rint = 0.073
9401 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.042313 parameters
wR(F2) = 0.0821 restraint
S = 0.95Δρmax = 1.22 e Å3
3400 reflectionsΔρmin = 1.04 e Å3
Special details top

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

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/UeqOcc. (<1)
Ge10.28732 (9)0.65515 (9)0.75805 (9)0.00966 (18)
Ge20.02820 (9)0.76641 (9)0.66405 (9)0.01171 (18)
Ge30.22611 (9)0.65845 (9)0.77842 (10)0.01260 (19)
Ge40.52220 (9)0.76621 (9)0.65123 (9)0.00997 (18)
Ge50.14459 (9)0.94746 (9)0.44097 (9)0.00897 (18)
Ge60.13837 (9)0.43761 (9)0.95231 (9)0.00935 (18)
Mn10.510.50.0091 (3)
Mn20.50.510.0099 (3)
Mn30.80868 (13)0.84635 (13)0.17711 (13)0.0101 (2)
Mn40.09944 (13)0.94628 (14)0.06221 (14)0.0119 (3)
Mn50.27496 (13)0.82376 (13)0.15887 (13)0.0107 (2)
Mn60.5914 (2)0.9367 (2)0.0598 (2)0.0108 (4)0.26
Na60.5914 (2)0.9367 (2)0.0598 (2)0.0108 (4)0.74
Mn70.48962 (13)0.72991 (13)0.26696 (13)0.0081 (2)
Na10.2913 (3)0.6300 (3)0.3830 (3)0.0149 (7)
Na20.1629 (3)0.6118 (4)0.3735 (4)0.0180 (7)
O10.1603 (6)0.8260 (6)0.9343 (6)0.0129 (12)
O20.4430 (6)0.4863 (6)0.7740 (6)0.0144 (12)
O30.1672 (5)0.6197 (6)0.6601 (6)0.0109 (11)
O40.3812 (6)0.6809 (6)0.6131 (6)0.0135 (11)
O50.1456 (5)0.9424 (6)0.8332 (6)0.0119 (11)
O60.1127 (6)0.6663 (6)0.6312 (6)0.0132 (11)
O70.0049 (5)0.7949 (5)0.4918 (6)0.0099 (11)
O80.3359 (6)0.8265 (6)0.9539 (6)0.0175 (13)
O90.0851 (6)0.4857 (6)0.7990 (6)0.0132 (12)
O100.3482 (6)0.6272 (6)0.6897 (6)0.0146 (12)
O110.6506 (6)0.9432 (6)0.8198 (6)0.0156 (12)
O120.4491 (6)0.7753 (6)0.4796 (6)0.0108 (11)
O130.2601 (6)1.1278 (6)0.6108 (6)0.0150 (12)
O140.2624 (6)0.8848 (6)0.3878 (6)0.0146 (12)
O150.0458 (6)0.9541 (6)0.2858 (6)0.0147 (12)
O160.2449 (6)0.6064 (6)1.1332 (6)0.0189 (13)
O170.0447 (6)0.2791 (6)0.9562 (6)0.0185 (13)
O180.2631 (6)0.3879 (6)0.8904 (6)0.0113 (11)
O190.4982 (6)0.9240 (6)0.2855 (6)0.0171 (12)
O200.5601 (6)0.7103 (6)0.0796 (6)0.0208 (13)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Ge10.0088 (4)0.0103 (4)0.0094 (4)0.0057 (3)0.0033 (3)0.0040 (3)
Ge20.0119 (4)0.0126 (4)0.0109 (4)0.0079 (3)0.0038 (3)0.0045 (3)
Ge30.0121 (4)0.0113 (4)0.0136 (4)0.0073 (3)0.0042 (3)0.0042 (3)
Ge40.0096 (4)0.0103 (4)0.0092 (4)0.0058 (3)0.0025 (3)0.0040 (3)
Ge50.0113 (4)0.0088 (4)0.0077 (4)0.0066 (3)0.0046 (3)0.0032 (3)
Ge60.0123 (4)0.0081 (4)0.0101 (4)0.0072 (3)0.0059 (3)0.0043 (3)
Mn10.0094 (7)0.0107 (8)0.0071 (8)0.0064 (6)0.0030 (6)0.0031 (6)
Mn20.0103 (7)0.0095 (8)0.0096 (8)0.0065 (6)0.0037 (6)0.0031 (6)
Mn30.0099 (5)0.0105 (5)0.0112 (6)0.0071 (5)0.0042 (5)0.0041 (5)
Mn40.0120 (5)0.0123 (5)0.0124 (6)0.0078 (5)0.0045 (5)0.0058 (5)
Mn50.0111 (5)0.0127 (6)0.0112 (6)0.0082 (5)0.0049 (5)0.0062 (5)
Mn60.0070 (9)0.0117 (10)0.0124 (10)0.0041 (8)0.0033 (8)0.0073 (8)
Na60.0070 (9)0.0117 (10)0.0124 (10)0.0041 (8)0.0033 (8)0.0073 (8)
Mn70.0104 (5)0.0094 (5)0.0081 (6)0.0075 (4)0.0044 (4)0.0043 (4)
Na10.0121 (14)0.0151 (15)0.0181 (16)0.0087 (12)0.0062 (12)0.0066 (13)
Na20.0147 (15)0.0229 (16)0.0167 (16)0.0111 (13)0.0052 (13)0.0101 (14)
O10.014 (2)0.012 (3)0.010 (3)0.009 (2)0.001 (2)0.001 (2)
O20.011 (2)0.016 (3)0.019 (3)0.008 (2)0.007 (2)0.009 (2)
O30.010 (2)0.009 (2)0.017 (3)0.008 (2)0.007 (2)0.004 (2)
O40.017 (2)0.018 (3)0.013 (3)0.016 (2)0.005 (2)0.004 (2)
O50.009 (2)0.013 (3)0.010 (3)0.006 (2)0.000 (2)0.003 (2)
O60.017 (3)0.017 (3)0.016 (3)0.014 (2)0.006 (2)0.011 (2)
O70.006 (2)0.006 (2)0.013 (3)0.001 (2)0.005 (2)0.004 (2)
O80.014 (3)0.012 (3)0.016 (3)0.005 (2)0.001 (2)0.003 (2)
O90.012 (2)0.009 (2)0.017 (3)0.006 (2)0.005 (2)0.005 (2)
O100.011 (2)0.012 (3)0.017 (3)0.005 (2)0.007 (2)0.006 (2)
O110.017 (3)0.007 (3)0.015 (3)0.005 (2)0.001 (2)0.002 (2)
O120.016 (2)0.012 (2)0.014 (3)0.011 (2)0.007 (2)0.010 (2)
O130.010 (2)0.011 (3)0.019 (3)0.005 (2)0.005 (2)0.006 (2)
O140.018 (3)0.016 (3)0.012 (3)0.011 (2)0.007 (2)0.005 (2)
O150.023 (3)0.015 (3)0.010 (3)0.014 (2)0.005 (2)0.006 (2)
O160.022 (3)0.017 (3)0.016 (3)0.012 (2)0.005 (2)0.006 (2)
O170.024 (3)0.011 (3)0.023 (3)0.012 (2)0.012 (2)0.007 (2)
O180.015 (3)0.013 (3)0.006 (3)0.009 (2)0.003 (2)0.003 (2)
O190.015 (3)0.017 (3)0.009 (3)0.006 (2)0.001 (2)0.004 (2)
O200.026 (3)0.016 (3)0.015 (3)0.013 (2)0.000 (2)0.003 (2)
Geometric parameters (Å, º) top
Ge1—O11.718 (5)Mn3—O5ii2.156 (5)
Ge1—O21.727 (5)Mn3—O1vii2.252 (5)
Ge1—O41.764 (5)Mn4—O11ii2.154 (5)
Ge1—O31.779 (5)Mn4—O152.175 (5)
Ge2—O51.706 (5)Mn4—O17viii2.186 (5)
Ge2—O71.740 (5)Mn4—O5ix2.200 (5)
Ge2—O31.754 (5)Mn4—O1x2.229 (5)
Ge2—O61.766 (5)Mn4—O1ix2.233 (5)
Ge3—O81.699 (5)Mn5—O191.969 (5)
Ge3—O91.730 (5)Mn5—O17viii1.994 (5)
Ge3—O101.733 (5)Mn5—O8ix2.053 (5)
Ge3—O61.768 (5)Mn5—O142.058 (5)
Ge4—O111.711 (5)Mn5—O11ii2.186 (5)
Ge4—O121.738 (5)Mn5—O16ix2.196 (5)
Ge4—O4i1.744 (5)Mn6—O8ix2.184 (5)
Ge4—O101.770 (5)Mn6—O5ii2.225 (5)
Ge5—O151.724 (5)Mn6—O8ii2.346 (5)
Ge5—O131.734 (5)Mn6—O11ix2.360 (6)
Ge5—O71.783 (5)Mn6—O192.389 (5)
Ge5—O141.784 (5)Mn6—O202.418 (6)
Ge6—O161.733 (5)Mn7—O201.947 (6)
Ge6—O171.748 (5)Mn7—O122.024 (5)
Ge6—O181.777 (5)Mn7—O192.071 (5)
Ge6—O91.789 (5)Mn7—O2viii2.073 (5)
Mn1—O19ii1.901 (5)Mn7—O13ii2.098 (5)
Mn1—O191.901 (5)Mn7—O16ix2.109 (5)
Mn1—O14ii2.020 (5)Na1—O72.362 (5)
Mn1—O142.020 (5)Na1—O2xi2.373 (5)
Mn1—O122.190 (5)Na1—O10viii2.430 (6)
Mn1—O12ii2.190 (5)Na1—O42.453 (6)
Mn2—O20iii1.918 (5)Na1—O13x2.513 (6)
Mn2—O20iv1.918 (5)Na1—O18viii2.522 (5)
Mn2—O18v2.017 (5)Na1—O32.805 (6)
Mn2—O182.017 (5)Na2—O9viii2.346 (6)
Mn2—O2i2.207 (5)Na2—O122.359 (5)
Mn2—O2vi2.207 (5)Na2—O16ix2.448 (6)
Mn3—O15i2.029 (5)Na2—O62.458 (6)
Mn3—O202.059 (5)Na2—O3viii2.538 (6)
Mn3—O18iii2.126 (5)Na2—O142.553 (6)
Mn3—O13ii2.146 (5)Na2—O6viii2.793 (6)
O1—Ge1—O2116.4 (2)O1x—Mn4—O1ix88.07 (18)
O1—Ge1—O4112.3 (2)O19—Mn5—O17viii176.1 (2)
O2—Ge1—O4105.9 (2)O19—Mn5—O8ix91.6 (2)
O1—Ge1—O3108.7 (2)O17viii—Mn5—O8ix92.2 (2)
O2—Ge1—O3111.5 (2)O19—Mn5—O1480.3 (2)
O4—Ge1—O3101.0 (2)O17viii—Mn5—O1496.0 (2)
O5—Ge2—O7111.7 (2)O8ix—Mn5—O14164.9 (2)
O5—Ge2—O3116.1 (2)O19—Mn5—O11ii90.5 (2)
O7—Ge2—O3104.6 (2)O17viii—Mn5—O11ii90.49 (19)
O5—Ge2—O6113.4 (2)O8ix—Mn5—O11ii79.7 (2)
O7—Ge2—O6107.4 (2)O14—Mn5—O11ii87.5 (2)
O3—Ge2—O6102.9 (2)O19—Mn5—O16ix81.1 (2)
O8—Ge3—O9113.8 (2)O17viii—Mn5—O16ix98.4 (2)
O8—Ge3—O10112.4 (2)O8ix—Mn5—O16ix93.8 (2)
O9—Ge3—O10106.9 (2)O14—Mn5—O16ix97.5 (2)
O8—Ge3—O6112.5 (2)O11ii—Mn5—O16ix169.3 (2)
O9—Ge3—O6105.3 (2)O8ix—Mn6—O5ii177.7 (2)
O10—Ge3—O6105.3 (2)O8ix—Mn6—O8ii88.91 (19)
O11—Ge4—O12116.3 (2)O5ii—Mn6—O8ii88.83 (19)
O11—Ge4—O4i108.3 (2)O8ix—Mn6—O11ix94.29 (19)
O12—Ge4—O4i111.0 (2)O5ii—Mn6—O11ix84.89 (18)
O11—Ge4—O10110.1 (2)O8ii—Mn6—O11ix70.57 (18)
O12—Ge4—O10105.9 (2)O8ix—Mn6—O1978.08 (19)
O15—Ge5—O13111.2 (2)O5ii—Mn6—O19102.65 (19)
O15—Ge5—O7108.3 (2)O8ii—Mn6—O19106.7 (2)
O13—Ge5—O7108.3 (2)O11ix—Mn6—O19172.06 (19)
O15—Ge5—O14114.3 (2)O8ix—Mn6—O2099.60 (19)
O13—Ge5—O14111.3 (2)O5ii—Mn6—O2082.65 (19)
O7—Ge5—O14102.9 (2)O8ii—Mn6—O20171.1 (2)
O16—Ge6—O17111.7 (2)O11ix—Mn6—O20106.03 (19)
O16—Ge6—O18111.7 (2)O19—Mn6—O2077.74 (19)
O17—Ge6—O18114.2 (2)O20—Mn7—O12172.1 (2)
O16—Ge6—O9107.7 (2)O20—Mn7—O1997.3 (2)
O17—Ge6—O9106.4 (2)O12—Mn7—O1981.29 (19)
O18—Ge6—O9104.4 (2)O20—Mn7—O2viii83.1 (2)
O19ii—Mn1—O19180.0000 (10)O12—Mn7—O2viii99.53 (19)
O19ii—Mn1—O14ii82.9 (2)O19—Mn7—O2viii170.94 (19)
O19—Mn1—O14ii97.1 (2)O20—Mn7—O13ii81.9 (2)
O19ii—Mn1—O1497.1 (2)O12—Mn7—O13ii90.46 (19)
O19—Mn1—O1482.9 (2)O19—Mn7—O13ii93.7 (2)
O14ii—Mn1—O14180.0000 (10)O2viii—Mn7—O13ii95.35 (19)
O19ii—Mn1—O1298.9 (2)O20—Mn7—O16ix95.1 (2)
O19—Mn1—O1281.1 (2)O12—Mn7—O16ix92.4 (2)
O14ii—Mn1—O1288.80 (19)O19—Mn7—O16ix80.90 (19)
O14—Mn1—O1291.20 (19)O2viii—Mn7—O16ix90.0 (2)
O19ii—Mn1—O12ii81.1 (2)O13ii—Mn7—O16ix173.4 (2)
O19—Mn1—O12ii98.9 (2)O7—Na1—O2xi161.8 (2)
O14ii—Mn1—O12ii91.20 (19)O7—Na1—O10viii97.99 (19)
O14—Mn1—O12ii88.80 (19)O2xi—Na1—O10viii93.29 (19)
O12—Mn1—O12ii180.0000 (10)O7—Na1—O4105.30 (19)
O20iii—Mn2—O20iv180.000 (2)O2xi—Na1—O484.37 (18)
O20iii—Mn2—O18v94.5 (2)O10viii—Na1—O4108.6 (2)
O20iv—Mn2—O18v85.5 (2)O7—Na1—O13x87.95 (18)
O20iii—Mn2—O1885.5 (2)O2xi—Na1—O13x78.24 (18)
O20iv—Mn2—O1894.5 (2)O10viii—Na1—O13x166.8 (2)
O18v—Mn2—O18180.0000 (10)O4—Na1—O13x80.94 (18)
O20iii—Mn2—O2i80.3 (2)O7—Na1—O18viii88.28 (18)
O20iv—Mn2—O2i99.7 (2)O2xi—Na1—O18viii77.89 (18)
O18v—Mn2—O2i86.51 (18)O10viii—Na1—O18viii87.76 (19)
O18—Mn2—O2i93.49 (18)O4—Na1—O18viii156.6 (2)
O20iii—Mn2—O2vi99.7 (2)O13x—Na1—O18viii80.60 (18)
O20iv—Mn2—O2vi80.3 (2)O7—Na1—O363.99 (16)
O18v—Mn2—O2vi93.49 (18)O2xi—Na1—O3133.75 (19)
O18—Mn2—O2vi86.51 (18)O10viii—Na1—O370.76 (17)
O15i—Mn3—O20171.1 (2)O4—Na1—O362.23 (16)
O15i—Mn3—O18iii93.35 (19)O13x—Na1—O3122.39 (18)
O20—Mn3—O18iii79.3 (2)O18viii—Na1—O3140.89 (18)
O15i—Mn3—O13ii98.16 (19)O9viii—Na2—O12154.9 (2)
O20—Mn3—O13ii78.2 (2)O9viii—Na2—O16ix84.28 (19)
O18iii—Mn3—O13ii99.33 (19)O12—Na2—O16ix76.69 (18)
O15i—Mn3—O5ii94.96 (19)O9viii—Na2—O698.88 (19)
O20—Mn3—O5ii93.5 (2)O12—Na2—O697.53 (19)
O18iii—Mn3—O5ii162.47 (18)O16ix—Na2—O6170.4 (2)
O13ii—Mn3—O5ii94.74 (19)O9viii—Na2—O3viii109.19 (19)
O15i—Mn3—O1vii92.65 (19)O12—Na2—O3viii85.57 (18)
O20—Mn3—O1vii92.08 (19)O16ix—Na2—O3viii85.07 (19)
O18iii—Mn3—O1vii87.04 (18)O6—Na2—O3viii102.30 (19)
O13ii—Mn3—O1vii167.07 (19)O9viii—Na2—O1485.16 (18)
O5ii—Mn3—O1vii77.19 (18)O12—Na2—O1475.47 (18)
O11ii—Mn4—O1591.72 (19)O16ix—Na2—O1479.49 (18)
O11ii—Mn4—O17viii86.43 (19)O6—Na2—O1491.68 (19)
O15—Mn4—O17viii82.95 (19)O3viii—Na2—O14157.8 (2)
O11ii—Mn4—O5ix90.65 (19)O9viii—Na2—O6viii64.82 (16)
O15—Mn4—O5ix176.84 (19)O12—Na2—O6viii139.52 (19)
O17viii—Mn4—O5ix99.29 (19)O16ix—Na2—O6viii120.15 (19)
O11ii—Mn4—O1x93.01 (18)O6—Na2—O6viii69.20 (19)
O15—Mn4—O1x101.01 (19)O3viii—Na2—O6viii61.97 (16)
O17viii—Mn4—O1x176.01 (19)O14—Na2—O6viii140.05 (19)
O5ix—Mn4—O1x76.76 (18)Ge2—O6—Ge3127.4 (3)
O11ii—Mn4—O1ix178.3 (2)Ge2—O7—Ge5126.2 (3)
O15—Mn4—O1ix89.36 (18)Ge3—O9—Ge6121.9 (3)
O17viii—Mn4—O1ix92.40 (19)Ge3—O10—Ge4127.6 (3)
O5ix—Mn4—O1ix88.33 (18)
Symmetry codes: (i) x+1, y, z; (ii) x+1, y+2, z+1; (iii) x+1, y+1, z+1; (iv) x, y, z+1; (v) x+1, y+1, z+2; (vi) x, y+1, z+2; (vii) x+1, y, z1; (viii) x, y+1, z+1; (ix) x, y, z1; (x) x, y+2, z+1; (xi) x1, y+1, z+1.

Experimental details

Crystal data
Chemical formulaNa2(Mn5.26Na0.74)Ge6O20
Mr1107.49
Crystal system, space groupTriclinic, P1
Temperature (K)295
a, b, c (Å)10.5578 (9), 11.1532 (7), 9.1833 (7)
α, β, γ (°)106.707 (2), 95.809 (1), 124.367 (5)
V3)806.05 (11)
Z2
Radiation typeMo Kα
µ (mm1)15.17
Crystal size (mm)0.09 × 0.07 × 0.04
Data collection
DiffractometerBruker SMART APEX
diffractometer
Absorption correctionNumerical
via equivalents using X-SHAPE (Stoe & Cie, 1996)
Tmin, Tmax0.29, 0.55
No. of measured, independent and
observed [I > 2σ(I)] reflections
9401, 3400, 2545
Rint0.073
(sin θ/λ)max1)0.633
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.042, 0.082, 0.95
No. of reflections3400
No. of parameters313
No. of restraints1
Δρmax, Δρmin (e Å3)1.22, 1.04

Computer programs: SMART-Plus (Bruker, 2001), SAINT-Plus (Bruker, 2001), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), DIAMOND (Version 3.0; Pennington, 1999), WinGX (Version 1.70.01; Farrugia, 1999).

Selected structural and distortional parameters for aenigmatite-type compounds. Literature data recalculated from fractional atomic coordinates and lattice parameters given in the Inorganic Crystal Structure database ICSD (···) top
NMnGNMgGWilkinsMg-AenigAenigRhöniteKrinovite
a (Å)10.557810.49510.335510.292510.406010.36710.238
b (Å)11.153210.87610.784710.705210.813010.75610.642
c (Å)9.18338.9948.91428..80278.92608.8958.770
α (°)106.707105.9105.048105.280104.930105.98105.15
β (°)95.80995.996.46196.71296.87096.0496.50
γ (°)124.367124.7125.302125.256125.320124.72125.15
M1—O Å2.0372.0462.0332.03782.0972.02382.0062
O—O Å2.8802.8912.8742.88052.9632.8602.8347
Vol (Å3)10.98611.26411.11311.21312.08810.93910.640
BLDa (%)5.060.851.160.903.060.361.28
OAVb (°)47.6731.1118.9814.6737.4623.1726.43
OQEc1.02071.00941.00601.00431.01221.00691.0080
Sd (v.u.)2.972.582.872.372.272.462.80
M2—O Å2.0472.0472.0522.06382.1002.0142.0124
O—O Å2.8942.8922.9012.91712.9672.8472.8432
Vol (Å3)11.15411.26511.40011.60612.09910.80410.7224
BLDa (%)5.190.972.781.993.170.261.52
OAVb (°)46.37433.80222.91121.55743.43920.02930.002
OQEc1.02071.01041.00831.00721.01481.00591.0092
Sd (v.u.)2.902.582.752.222.092.512.81
M3—O Å2.1282.0742.1382.1002.1342.0832.093
O—O Å3.0042.9273.0142.9673.0062.9412.956
Vol (Å3)12.49211.66612.66312.21412.53011.82812.090
BLDa (%)2.661.833.251.403.170.791.24
OAVb (°)60.14642.72163.42926.59575.41440.21025.339
OQEc1.01981.01351.02091.00801.02451.01211.0073
Sd (v.u.)2.452.412.062.012.092.092.04
M4—O Å2.1962.0932.1452.1012.1572.0432.092
O—O Å3.1012.9553.0292.9593.0472.8832.951
Vol (Å3)13.87212.04612.99412.06513.20411.17911.931
BLDa (%)1.100.901.682.181.431.702.04
OAVb (°)42.76133.10530.89856.43631.94235.49251.919
OQEc1.01231.01001.00931.01711.00951.01131.0162
Sd (v.u.)2.012.041.992.011.922.352.06
M5—O Å2.0762.0772.1292.0822.1302.0352.083
O—O Å2.9322.9302.9992.9302.9982.8722.935
Vol (Å3)11.67711.71212.55611.75212.51111.07311.772
BLDa (%)3.671.692.622.072.371.501.92
OAVb (°)42.73744.83953.81854.83764.53330.98451.957
OQEc1.01621.01401.01741.01681.02031.00981.0163
Sd (v.u.)2.612.392.092.122.092.402.11
M6—O Å2.3212.1392.1562.1002.14852.1182.115
O—O Å3.2703.0153.0432.9653.0322.9882.984
Vol (Å3)15.59612.51212.95212.03712.70412.18612.221
BLDa (%)3.281.631.091.201.101.810.67
OAVb (°)141.75889.62973.90456.88988.39281.61372.076
OQEc1.04661.02821.02171.01751.02731.0261.0215
Sd (v.u.)1.471.911.922.001.961.921.92
M7—O Å2.0542.0342.0372.0371.9892.0401.999
O—O Å2.9032.8762.8812.8742.81512.8852.827
Vol (Å3)11.32411.08411.13311.11010.41011.16710.520
BLDa (%)2.212.722.011.064.473.592.82
OAVb (°)44.61027.42528.53734.45617.91830.84426.539
OQEc1.01401.00861.00871.01001.00781.01031.0088
Sd (v.u.)2.742.712.852.373.142.412.90
T1—O Å1.7471.7661.6371.6211.6511.70981.624
O—O Å2.8472.8762.6692.6442.6922.7872.650
Vol (Å3)2.7092.7912.2322.1732.2882.5412.190
BLDa (%)1.370.631.251.440.830.421.06
TAVe (°)29.01634.26224.71915.81028.16327.05412.434
TQEf1.00701.00831.00591.00371.00671.00641.0029
Sd (v.u.)4.033.824.053.713.17
T2—O Å1.7421.7501.6321.6311.6541.7241.616
O—O Å2.8382.8532.6632.6632.7002.8102.637
Vol (Å3)2.6862.7282.2222.2212.3162.5922.154
BLDa (%)0.940.630.980.970.380.331.11
TAVe (°)26.99522.80612.4988.83010.02436.36914.913
TQEf1.00611.00531.00291.00221.00241.00971.0036
Sd (v.u.)4.073.983.923.683.05
T3—O Å1.7331.7351.6211.6251.6271.6751.628
O—O Å2.8262.8292.6452.6492.6562.7312.654
Vol (Å3)2.6562.6622.1782.1782.2062.3932.189
BLDa (%)1.080.460.911.100.590.740.90
TAVe (°)15.62617.66510.76230.3398.08020.27033.702
TQEf1.00351.00411.00261.00711.00191.00481.0079
Sd (v.u.)4.154.154.003.973.49
T4—O Å1.7411.7501.6311.6461.6271.6921.640
O—O Å2.8392.8512.6592.6832.6532.7582.673
Vol (Å3)2.6922.7192.2062.2662.1932.4582.238
BLDa (%)0.970.450.891.441.190.230.69
TAVe (°)17.46434.44224.39029.32321.41130.19229.194
TQEf1.00411.00821.00571.00711.00511.00771.0072
Sd (v.u.)4.073.973.783.973.28
T5—O Å1.7561.7591.6371.6431.6401.7371.639
O—O Å2.8652.8682.6702.6792.6762.8342.674
Vol (Å3)2.7662.7772.2372.2582.2542.6712.249
BLDa (%)1.620.721.071.561.071.451.43
TAVe (°)14.99316.13714.72420.0729.63017.68214.319
TQEf1.00381.00401.00371.00521.00251.00521.0036
Sd (v.u.)3.923.883.823.842.92
T6—O Å1.7621.7601.6351.6431.6321.7431.640
O—O Å2.8742.8682.6672.6792.6622.8422.674
Vol (Å3)2.7922.7742.2312.2592.2192.6922.248
BLDa (%)1.300.811.021.091.161.691.13
TAVe (°)14.12422.93714.22022.51912.52020.32218.229
TQEf1.00361.00581.00351.00571.00301.00621.0045
Sd (v.u.)3.873.873.803.922.88
O4—O3—O6149.69145.94160.50160.26160.75155.48162.18
O3—O6—O10152.05148.16163.89150.98163.15149.56152.99
O6—O10—O4142.84141.04154.11148.90154.10146.52149.50
O10—O4—O3140.92138.53150.80157.98151.81152.20158.61
O—O–O146.38143.32157.33154.528157.45150.94155.82
CN A1g6+16+17+17+17+17+17+1
A1—O2.4942.4472.5442.5252.5482.5162.512
A1—Olongh2.8052.8562.9653.0112.9483.0162.965
A1—O6.72.4402.3972.4842.4562.4902.4352.447
Sd (v.u.)1.151.281.221.112.041.25
CN A2g6+16+17+17+17+17+17+1
A2—O2.4992.4632.5572.5442.5702.5292.524
A2—Olongh2.7932.8302.9833.0152.9693.0562.953
A2—Oinner2.4502.4022.4962.4772.5132.4442.463
Sd (v.u.)1.141.201.191.071.981.21
NMnG = title compound, this study; NMgG = Na2(Mg3.6Fe2.4)[(Ge5.6Fe0.4)O18]O20 (Barbier, 1995); Wilkins = wilkinsonite, Na2Fe2+4Fe3+2Si6O20 (Burt et al., 2007); Mg-Aenig = Mg-Aenigmatite, Na2Mg6Si6O18(OH)2 (Yang & Konzett, 2000); Aenig = Aenigmatite, Na2Fe5TiSi6O20 (Cannillo et al., 1971); Rhönite = Ca2(Mg, Fe, Ti)6Si6O20 (Bonaccorsi et al., 1990); Krinovite = Na2Mg4Cr2Si6O20 (Bonaccorsi et al., 1989).

(a) Bond length distortion, BLD = (100/n)Σi = 1n[{(X—O)i-(x—O)}/(X—O)], with n = number of bonds, (X—O)i = central cation-to-oxygen length and X—O = average cation–oxygen bond length (Renner & Lehmann, 1986). (b) Octahedral angle variance, OAV = Σi=1n(Θi-90)2/11 (Robinson et al., 1971). (c) Octahedral quadratic elongation, OQE = Σi=16(li/lo)2/6, with lo = centre-to-vertex distance for a regular octahedron whose volume is equal to that of the undistorted octahedron with bond length li (Robinson et al., 1971). (d) Bond valence sum, S (Brese & O'Keeffe, 1991). (e) Tetrahedral angle variance, TAV = Σi=1n(Θi-109.47)2/5 (Robinson et al., 1971). (f) Tetrahedral quadratic elongation, TQE = Σi=14(li/lt)2/4, with lt = centre-to-vertex distance for a regular tetrahedron whose volume is equal to that of the undistorted tetrahedron with bond length li (Robinson et al., 1971). (g) CN = number of A1 (Na, Ca) coordinating O atoms. (h) Denotes the longest A—O bond length.
 

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