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The structure of metastable, incommensurately modulated Na2Si3O7 has been determined from single-crystal X-ray diffraction data. In contrast to previous investigations which stated that the compound crystallizes in an orthorhombic space group, this study shows that the compound is monoclinic with a pseudo-orthorhombic cell and is affected by twinning. The structure is described in the (3 + 1)-dimensional superspace. Crenel-type modulation functions are used to account for an aperiodic sequence of right- and left-handed zweier single chains of silicate tetrahedra. The modulation mainly affects one of the two symmetrically independent tetrahedral chains, which are connected to build up [Si3O7]2- layers. Sodium cations are coordinated by five oxygen ligands and provide linkage between adjacent tetrahedral sheets. Distortions of the silicate tetrahedra and crystal chemical relationships of the title compound to sodium and lithium di- and metasilicates are discussed in detail.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S010876810600663X/sn5035sup1.cif
Contains datablocks global, I

pdf

Portable Document Format (PDF) file https://doi.org/10.1107/S010876810600663X/sn5035sup2.pdf
Bond-valence sums, bonding angles, volume, quadratic elongation and tetrahedral angle variance graphs

Computing details top

Data collection: STOE X-AREA; cell refinement: STOE X-AREA; data reduction: STOE X-RED; program(s) used to solve structure: SIR97; program(s) used to refine structure: (Jana2000; Petricek and Dusek, 2000); software used to prepare material for publication: (Jana2000; Petricek and Dusek, 2000).

Figures top
[Figure 1]
[Figure 2]
[Figure 3]
[Figure 4]
[Figure 5]
[Figure 6]
[Figure 7]
[Figure 8]
[Figure 9]
(I) top
Crystal data top
Na2O7Si3F(000) = 480
Mr = 242.2Dx = 2.459 Mg m3
Monoclinic, C2/c(0β0)s0†Mo Kα radiation, λ = 0.71073 Å
q = 0.56160b*Cell parameters from 2604 reflections
a = 20.416 (6) Åθ = 2.0–27.0°
b = 6.4987 (15) ŵ = 0.85 mm1
c = 4.9294 (19) ÅT = 298 K
β = 90.26 (3)°Plate, colourless
V = 654.0 (4) Å30.28 × 0.1 × 0.03 mm
Z = 4
† Symmetry operations: (1) x1, x2, x3, x4; (2) −x1, x2, 1/2−x3, 1/2+x4; (3) −x1, −x2, −x3, −x4; (4) x1, −x2, 1/2+x3, 1/2−x4; (5) 1/2+x1, 1/2+x2, x3, x4; (6) 1/2−x1, 1/2+x2, 1/2−x3, 1/2+x4; (7) 1/2−x1, 1/2−x2, −x3, −x4; (8) 1/2+x1, 1/2−x2, 1/2+x3, 1/2−x4.

Data collection top
STOE IPDS 2
diffractometer
1327 reflections with I > 3σ(I)
Radiation source: sealed X-ray tube, 12 x 0.4 mm long-fine focusRint = 0.082
Plane graphite monochromatorθmax = 26.7°, θmin = 1.7°
Detector resolution: 6.67 pixels mm-1h = 2525
rotation method scansk = 88
4714 measured reflectionsl = 64
1914 independent reflections
Refinement top
Refinement on F157 parameters
R[F2 > 2σ(F2)] = 0.073Weighting scheme based on measured s.u.'s w = 1/(σ2(F) + 0.0001F2)
wR(F2) = 0.065(Δ/σ)max = 0.0004
S = 2.30Δρmax = 1.07 e Å3
1914 reflectionsΔρmin = 0.80 e Å3
Crystal data top
Na2O7Si3β = 90.26 (3)°
Mr = 242.2V = 654.0 (4) Å3
Monoclinic, C2/c(0β0)s0†Z = 4
q = 0.56160b*Mo Kα radiation
a = 20.416 (6) ŵ = 0.85 mm1
b = 6.4987 (15) ÅT = 298 K
c = 4.9294 (19) Å0.28 × 0.1 × 0.03 mm
† Symmetry operations: (1) x1, x2, x3, x4; (2) −x1, x2, 1/2−x3, 1/2+x4; (3) −x1, −x2, −x3, −x4; (4) x1, −x2, 1/2+x3, 1/2−x4; (5) 1/2+x1, 1/2+x2, x3, x4; (6) 1/2−x1, 1/2+x2, 1/2−x3, 1/2+x4; (7) 1/2−x1, 1/2−x2, −x3, −x4; (8) 1/2+x1, 1/2−x2, 1/2+x3, 1/2−x4.

Data collection top
STOE IPDS 2
diffractometer
1327 reflections with I > 3σ(I)
4714 measured reflectionsRint = 0.082
1914 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.073157 parameters
wR(F2) = 0.065Δρmax = 1.07 e Å3
S = 2.30Δρmin = 0.80 e Å3
1914 reflections
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
Si10.13414 (6)0.3581 (2)0.2013 (3)0.0218 (4)
Si200.1359 (3)0.1855 (4)0.0177 (5)
O10.35972 (18)0.0666 (5)0.1199 (7)0.0283 (11)
O20.19026 (14)0.1984 (4)0.2567 (7)0.0216 (10)
O30.0137 (3)0.0607 (8)0.3781 (10)0.0303 (17)
O40.06199 (17)0.2664 (7)0.2426 (8)0.0273 (12)
Na10.29570 (9)0.3515 (3)0.2653 (4)0.0263 (5)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Si10.0243 (6)0.0201 (6)0.0208 (6)0.0023 (6)0.0034 (6)0.0010 (6)
Si20.0217 (9)0.0184 (8)0.0130 (11)0.0008 (8)0.0016 (10)0.0005 (9)
O10.040 (2)0.0226 (17)0.0225 (18)0.0010 (15)0.0030 (15)0.0010 (15)
O20.0310 (17)0.0210 (14)0.0129 (19)0.0032 (12)0.0023 (16)0.0020 (13)
O30.052 (3)0.027 (3)0.012 (3)0.009 (2)0.001 (2)0.005 (2)
O40.0260 (16)0.028 (2)0.028 (2)0.0037 (16)0.000 (2)0.004 (2)
Na10.0372 (11)0.0234 (7)0.0184 (9)0.0012 (9)0.0011 (9)0.0022 (9)
Geometric parameters (Å, º) top
AverageMinimumMaximum
Si1—O1i1.664 (8)1.603 (8)1.723 (8)
Si1—O1ii1.628 (7)1.583 (7)1.665 (7)
Si1—O21.575 (7)1.567 (7)1.582 (6)
Si1—O41.615 (7)1.591 (7)1.642 (7)
Si2—O31.608 (6)1.599 (6)1.633 (6)
Si2—O3iii2.847 (6)2.847 (6)2.847 (6)
Si2—O3iv2.236 (6)2.236 (6)2.236 (6)
Si2—O3v1.607 (5)1.598 (5)1.631 (6)
Si2—O41.594 (7)1.538 (8)1.641 (7)
Si2—O4vi1.589 (8)1.563 (8)1.619 (8)
Na1—O12.384 (7)2.339 (8)2.429 (8)
Na1—O22.372 (7)2.328 (7)2.416 (7)
Na1—O2i2.610 (8)2.579 (8)2.643 (9)
Na1—O2vii2.395 (8)2.359 (9)2.430 (9)
Na1—O2ii2.291 (7)2.256 (7)2.326 (7)
O1i—Si1—O1vii153.7 (3)152.5 (3)154.7 (3)
O1i—Si1—O1ii105.3 (4)104.2 (4)106.5 (4)
O1i—Si1—O2107.5 (4)105.9 (4)109.3 (4)
O1i—Si1—O4107.6 (4)105.9 (4)109.5 (4)
O1i—Si1—O4viii40.9 (3)39.0 (3)43.4 (3)
O1ii—Si1—O1i105.3 (4)104.2 (4)106.5 (4)
O1ii—Si1—O1vii48.9 (3)46.8 (3)50.6 (3)
O1ii—Si1—O2113.9 (4)112.0 (4)115.7 (4)
O1ii—Si1—O4108.2 (4)106.2 (4)110.2 (4)
O1ii—Si1—O4viii78.5 (3)76.5 (3)81.2 (3)
O2—Si1—O4113.8 (4)110.5 (4)117.3 (4)
O2—Si1—O4viii147.9 (3)144.6 (3)151.2 (3)
O4—Si1—O4viii87.5 (3)86.3 (3)89.0 (3)
O3—Si2—O3iii117.2 (2)117.2 (2)117.2 (2)
O3—Si2—O3iv43.5 (2)43.5 (2)43.5 (2)
O3—Si2—O3v107.2 (3)104.9 (3)108.1 (3)
O3—Si2—O4109.4 (4)104.3 (4)118.7 (4)
O3—Si2—O4iii71.8 (2)71.2 (2)73.0 (2)
O3—Si2—O4vi109.8 (4)98.3 (4)115.9 (4)
O3iii—Si2—O3117.2 (2)117.2 (2)117.2 (2)
O3iii—Si2—O3iv151.5 (2)151.5 (2)151.5 (2)
O3iii—Si2—O4100.0 (3)100.0 (3)100.0 (3)
O3iii—Si2—O4iii48.22 (17)48.22 (17)48.22 (17)
O3iii—Si2—O4vi114.1 (3)114.1 (3)114.1 (3)
O3iv—Si2—O343.5 (2)43.5 (2)43.5 (2)
O3iv—Si2—O3iii151.5 (2)151.5 (2)151.5 (2)
O3iv—Si2—O480.9 (4)80.9 (4)80.9 (4)
O3iv—Si2—O4iii116.3 (2)116.3 (2)116.3 (2)
O3iv—Si2—O4vi91.9 (4)91.9 (4)91.9 (4)
O3v—Si2—O3107.2 (3)104.9 (3)108.1 (3)
O3v—Si2—O4112.0 (4)108.4 (4)119.5 (4)
O3v—Si2—O4iii35.7 (2)32.7 (2)37.0 (2)
O3v—Si2—O4vi108.4 (4)104.3 (4)110.3 (4)
O4—Si2—O4iii129.7 (3)122.2 (3)141.7 (3)
O4—Si2—O4vi109.5 (4)108.7 (4)109.9 (4)
O4vi—Si2—O4109.5 (4)108.7 (4)109.9 (4)
O4vi—Si2—O4iii117.0 (3)104.4 (3)124.1 (3)
O1—Na1—O299.6 (3)95.9 (3)103.5 (3)
O1—Na1—O2i62.9 (2)62.0 (2)63.6 (2)
O1—Na1—O2vii97.3 (3)95.8 (3)98.9 (3)
O1—Na1—O2ii133.3 (3)122.5 (3)143.7 (3)
O2—Na1—O2i91.9 (3)91.2 (3)92.7 (3)
O2—Na1—O2vii93.8 (3)93.6 (3)93.9 (3)
O2—Na1—O2ii121.9 (3)113.0 (3)130.8 (3)
O2i—Na1—O291.9 (3)91.2 (3)92.7 (3)
O2i—Na1—O2vii160.0 (3)159.3 (3)160.7 (3)
O2i—Na1—O2ii93.6 (3)92.3 (3)94.7 (3)
O2vii—Na1—O293.8 (3)93.6 (3)93.9 (3)
O2vii—Na1—O2i160.0 (3)159.3 (3)160.7 (3)
O2vii—Na1—O2ii99.5 (3)98.6 (3)100.5 (3)
O2ii—Na1—O2121.9 (3)113.0 (3)130.8 (3)
O2ii—Na1—O2i93.6 (3)92.3 (3)94.7 (3)
O2ii—Na1—O2vii99.5 (3)98.6 (3)100.5 (3)
Symmetry codes: (i) x1+1/2, x2+1/2, x3, x4; (ii) x1+1/2, x2+1/2, x3+1/2, x1/2; (iii) x1, x2, x3, x4; (iv) x1, x2, x3+1, x4; (v) x1, x2, x31/2, x1/2; (vi) x1, x2, x3+1/2, x1/2; (vii) x1+1/2, x2+1/2, x3+1, x4; (viii) x1, x2+1, x31/2, x1/2.

Experimental details

Crystal data
Chemical formulaNa2O7Si3
Mr242.2
Crystal system, space groupMonoclinic, C2/c(0β0)s0†
Temperature (K)298
Wave vectorsq = 0.56160b*
a, b, c (Å)20.416 (6), 6.4987 (15), 4.9294 (19)
β (°) 90.26 (3)
V3)654.0 (4)
Z4
Radiation typeMo Kα
µ (mm1)0.85
Crystal size (mm)0.28 × 0.1 × 0.03
Data collection
DiffractometerSTOE IPDS 2
diffractometer
Absorption correction
No. of measured, independent and
observed [I > 3σ(I)] reflections
4714, 1914, 1327
Rint0.082
(sin θ/λ)max1)0.632
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.073, 0.065, 2.30
No. of reflections1914
No. of parameters157
No. of restraints?
Δρmax, Δρmin (e Å3)1.07, 0.80

† Symmetry operations: (1) x1, x2, x3, x4; (2) −x1, x2, 1/2−x3, 1/2+x4; (3) −x1, −x2, −x3, −x4; (4) x1, −x2, 1/2+x3, 1/2−x4; (5) 1/2+x1, 1/2+x2, x3, x4; (6) 1/2−x1, 1/2+x2, 1/2−x3, 1/2+x4; (7) 1/2−x1, 1/2−x2, −x3, −x4; (8) 1/2+x1, 1/2−x2, 1/2+x3, 1/2−x4.

Computer programs: STOE X-AREA, STOE X-RED, SIR97, (Jana2000; Petricek and Dusek, 2000).

Selected geometric parameters (Å, º) top
AverageMinimumMaximum
Si1—O1i1.664 (8)1.603 (8)1.723 (8)
Si1—O1ii1.628 (7)1.583 (7)1.665 (7)
Si1—O21.575 (7)1.567 (7)1.582 (6)
Si1—O41.615 (7)1.591 (7)1.642 (7)
Si2—O31.608 (6)1.599 (6)1.633 (6)
Si2—O3iii2.847 (6)2.847 (6)2.847 (6)
Si2—O3iv2.236 (6)2.236 (6)2.236 (6)
Si2—O3v1.607 (5)1.598 (5)1.631 (6)
Si2—O41.594 (7)1.538 (8)1.641 (7)
Si2—O4vi1.589 (8)1.563 (8)1.619 (8)
Na1—O12.384 (7)2.339 (8)2.429 (8)
Na1—O22.372 (7)2.328 (7)2.416 (7)
Na1—O2i2.610 (8)2.579 (8)2.643 (9)
Na1—O2vii2.395 (8)2.359 (9)2.430 (9)
Na1—O2ii2.291 (7)2.256 (7)2.326 (7)
O1i—Si1—O1vii153.7 (3)152.5 (3)154.7 (3)
O1i—Si1—O1ii105.3 (4)104.2 (4)106.5 (4)
O1i—Si1—O2107.5 (4)105.9 (4)109.3 (4)
O1i—Si1—O4107.6 (4)105.9 (4)109.5 (4)
O1i—Si1—O4viii40.9 (3)39.0 (3)43.4 (3)
O1ii—Si1—O1i105.3 (4)104.2 (4)106.5 (4)
O1ii—Si1—O1vii48.9 (3)46.8 (3)50.6 (3)
O1ii—Si1—O2113.9 (4)112.0 (4)115.7 (4)
O1ii—Si1—O4108.2 (4)106.2 (4)110.2 (4)
O1ii—Si1—O4viii78.5 (3)76.5 (3)81.2 (3)
O2—Si1—O4113.8 (4)110.5 (4)117.3 (4)
O2—Si1—O4viii147.9 (3)144.6 (3)151.2 (3)
O4—Si1—O4viii87.5 (3)86.3 (3)89.0 (3)
O3—Si2—O3iii117.2 (2)117.2 (2)117.2 (2)
O3—Si2—O3iv43.5 (2)43.5 (2)43.5 (2)
O3—Si2—O3v107.2 (3)104.9 (3)108.1 (3)
O3—Si2—O4109.4 (4)104.3 (4)118.7 (4)
O3—Si2—O4iii71.8 (2)71.2 (2)73.0 (2)
O3—Si2—O4vi109.8 (4)98.3 (4)115.9 (4)
O3iii—Si2—O3117.2 (2)117.2 (2)117.2 (2)
O3iii—Si2—O3iv151.5 (2)151.5 (2)151.5 (2)
O3iii—Si2—O4100.0 (3)100.0 (3)100.0 (3)
O3iii—Si2—O4iii48.22 (17)48.22 (17)48.22 (17)
O3iii—Si2—O4vi114.1 (3)114.1 (3)114.1 (3)
O3iv—Si2—O343.5 (2)43.5 (2)43.5 (2)
O3iv—Si2—O3iii151.5 (2)151.5 (2)151.5 (2)
O3iv—Si2—O480.9 (4)80.9 (4)80.9 (4)
O3iv—Si2—O4iii116.3 (2)116.3 (2)116.3 (2)
O3iv—Si2—O4vi91.9 (4)91.9 (4)91.9 (4)
O3v—Si2—O3107.2 (3)104.9 (3)108.1 (3)
O3v—Si2—O4112.0 (4)108.4 (4)119.5 (4)
O3v—Si2—O4iii35.7 (2)32.7 (2)37.0 (2)
O3v—Si2—O4vi108.4 (4)104.3 (4)110.3 (4)
O4—Si2—O4iii129.7 (3)122.2 (3)141.7 (3)
O4—Si2—O4vi109.5 (4)108.7 (4)109.9 (4)
O4vi—Si2—O4109.5 (4)108.7 (4)109.9 (4)
O4vi—Si2—O4iii117.0 (3)104.4 (3)124.1 (3)
O1—Na1—O299.6 (3)95.9 (3)103.5 (3)
O1—Na1—O2i62.9 (2)62.0 (2)63.6 (2)
O1—Na1—O2vii97.3 (3)95.8 (3)98.9 (3)
O1—Na1—O2ii133.3 (3)122.5 (3)143.7 (3)
O2—Na1—O2i91.9 (3)91.2 (3)92.7 (3)
O2—Na1—O2vii93.8 (3)93.6 (3)93.9 (3)
O2—Na1—O2ii121.9 (3)113.0 (3)130.8 (3)
O2i—Na1—O291.9 (3)91.2 (3)92.7 (3)
O2i—Na1—O2vii160.0 (3)159.3 (3)160.7 (3)
O2i—Na1—O2ii93.6 (3)92.3 (3)94.7 (3)
O2vii—Na1—O293.8 (3)93.6 (3)93.9 (3)
O2vii—Na1—O2i160.0 (3)159.3 (3)160.7 (3)
O2vii—Na1—O2ii99.5 (3)98.6 (3)100.5 (3)
O2ii—Na1—O2121.9 (3)113.0 (3)130.8 (3)
O2ii—Na1—O2i93.6 (3)92.3 (3)94.7 (3)
O2ii—Na1—O2vii99.5 (3)98.6 (3)100.5 (3)
Symmetry codes: (i) x1+1/2, x2+1/2, x3, x4; (ii) x1+1/2, x2+1/2, x3+1/2, x1/2; (iii) x1, x2, x3, x4; (iv) x1, x2, x3+1, x4; (v) x1, x2, x31/2, x1/2; (vi) x1, x2, x3+1/2, x1/2; (vii) x1+1/2, x2+1/2, x3+1, x4; (viii) x1, x2+1, x31/2, x1/2.
 

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