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
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).
Crystal data top
Na2O7Si3 | F(000) = 480 |
Mr = 242.2 | Dx = 2.459 Mg m−3 |
Monoclinic, C2/c(0β0)s0† | Mo Kα radiation, λ = 0.71073 Å |
q = 0.56160b* | Cell parameters from 2604 reflections |
a = 20.416 (6) Å | θ = 2.0–27.0° |
b = 6.4987 (15) Å | µ = 0.85 mm−1 |
c = 4.9294 (19) Å | T = 298 K |
β = 90.26 (3)° | Plate, colourless |
V = 654.0 (4) Å3 | 0.28 × 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.
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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 focus | Rint = 0.082 |
Plane graphite monochromator | θmax = 26.7°, θmin = 1.7° |
Detector resolution: 6.67 pixels mm-1 | h = −25→25 |
rotation method scans | k = −8→8 |
4714 measured reflections | l = −6→4 |
1914 independent reflections | |
Refinement top
Refinement on F | 157 parameters |
R[F2 > 2σ(F2)] = 0.073 | Weighting scheme based on measured s.u.'s w = 1/(σ2(F) + 0.0001F2) |
wR(F2) = 0.065 | (Δ/σ)max = 0.0004 |
S = 2.30 | Δρmax = 1.07 e Å−3 |
1914 reflections | Δρmin = −0.80 e Å−3 |
Crystal data top
Na2O7Si3 | β = 90.26 (3)° |
Mr = 242.2 | V = 654.0 (4) Å3 |
Monoclinic, C2/c(0β0)s0† | Z = 4 |
q = 0.56160b* | Mo Kα radiation |
a = 20.416 (6) Å | µ = 0.85 mm−1 |
b = 6.4987 (15) Å | T = 298 K |
c = 4.9294 (19) Å | 0.28 × 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.
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Data collection top
STOE IPDS 2 diffractometer | 1327 reflections with I > 3σ(I) |
4714 measured reflections | Rint = 0.082 |
1914 independent reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.073 | 157 parameters |
wR(F2) = 0.065 | Δρmax = 1.07 e Å−3 |
S = 2.30 | Δρmin = −0.80 e Å−3 |
1914 reflections | |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | |
Si1 | 0.13414 (6) | 0.3581 (2) | 0.2013 (3) | 0.0218 (4) | |
Si2 | 0 | 0.1359 (3) | 0.1855 (4) | 0.0177 (5) | |
O1 | 0.35972 (18) | 0.0666 (5) | 0.1199 (7) | 0.0283 (11) | |
O2 | 0.19026 (14) | 0.1984 (4) | 0.2567 (7) | 0.0216 (10) | |
O3 | −0.0137 (3) | −0.0607 (8) | 0.3781 (10) | 0.0303 (17) | |
O4 | 0.06199 (17) | 0.2664 (7) | 0.2426 (8) | 0.0273 (12) | |
Na1 | 0.29570 (9) | 0.3515 (3) | 0.2653 (4) | 0.0263 (5) | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
Si1 | 0.0243 (6) | 0.0201 (6) | 0.0208 (6) | −0.0023 (6) | 0.0034 (6) | −0.0010 (6) |
Si2 | 0.0217 (9) | 0.0184 (8) | 0.0130 (11) | 0.0008 (8) | 0.0016 (10) | 0.0005 (9) |
O1 | 0.040 (2) | 0.0226 (17) | 0.0225 (18) | 0.0010 (15) | 0.0030 (15) | −0.0010 (15) |
O2 | 0.0310 (17) | 0.0210 (14) | 0.0129 (19) | 0.0032 (12) | −0.0023 (16) | −0.0020 (13) |
O3 | 0.052 (3) | 0.027 (3) | 0.012 (3) | −0.009 (2) | 0.001 (2) | 0.005 (2) |
O4 | 0.0260 (16) | 0.028 (2) | 0.028 (2) | −0.0037 (16) | 0.000 (2) | 0.004 (2) |
Na1 | 0.0372 (11) | 0.0234 (7) | 0.0184 (9) | −0.0012 (9) | 0.0011 (9) | −0.0022 (9) |
Geometric parameters (Å, º) top | Average | Minimum | Maximum |
Si1—O1i | 1.664 (8) | 1.603 (8) | 1.723 (8) |
Si1—O1ii | 1.628 (7) | 1.583 (7) | 1.665 (7) |
Si1—O2 | 1.575 (7) | 1.567 (7) | 1.582 (6) |
Si1—O4 | 1.615 (7) | 1.591 (7) | 1.642 (7) |
Si2—O3 | 1.608 (6) | 1.599 (6) | 1.633 (6) |
Si2—O3iii | 2.847 (6) | 2.847 (6) | 2.847 (6) |
Si2—O3iv | 2.236 (6) | 2.236 (6) | 2.236 (6) |
Si2—O3v | 1.607 (5) | 1.598 (5) | 1.631 (6) |
Si2—O4 | 1.594 (7) | 1.538 (8) | 1.641 (7) |
Si2—O4vi | 1.589 (8) | 1.563 (8) | 1.619 (8) |
Na1—O1 | 2.384 (7) | 2.339 (8) | 2.429 (8) |
Na1—O2 | 2.372 (7) | 2.328 (7) | 2.416 (7) |
Na1—O2i | 2.610 (8) | 2.579 (8) | 2.643 (9) |
Na1—O2vii | 2.395 (8) | 2.359 (9) | 2.430 (9) |
Na1—O2ii | 2.291 (7) | 2.256 (7) | 2.326 (7) |
| | | |
O1i—Si1—O1vii | 153.7 (3) | 152.5 (3) | 154.7 (3) |
O1i—Si1—O1ii | 105.3 (4) | 104.2 (4) | 106.5 (4) |
O1i—Si1—O2 | 107.5 (4) | 105.9 (4) | 109.3 (4) |
O1i—Si1—O4 | 107.6 (4) | 105.9 (4) | 109.5 (4) |
O1i—Si1—O4viii | 40.9 (3) | 39.0 (3) | 43.4 (3) |
O1ii—Si1—O1i | 105.3 (4) | 104.2 (4) | 106.5 (4) |
O1ii—Si1—O1vii | 48.9 (3) | 46.8 (3) | 50.6 (3) |
O1ii—Si1—O2 | 113.9 (4) | 112.0 (4) | 115.7 (4) |
O1ii—Si1—O4 | 108.2 (4) | 106.2 (4) | 110.2 (4) |
O1ii—Si1—O4viii | 78.5 (3) | 76.5 (3) | 81.2 (3) |
O2—Si1—O4 | 113.8 (4) | 110.5 (4) | 117.3 (4) |
O2—Si1—O4viii | 147.9 (3) | 144.6 (3) | 151.2 (3) |
O4—Si1—O4viii | 87.5 (3) | 86.3 (3) | 89.0 (3) |
O3—Si2—O3iii | 117.2 (2) | 117.2 (2) | 117.2 (2) |
O3—Si2—O3iv | 43.5 (2) | 43.5 (2) | 43.5 (2) |
O3—Si2—O3v | 107.2 (3) | 104.9 (3) | 108.1 (3) |
O3—Si2—O4 | 109.4 (4) | 104.3 (4) | 118.7 (4) |
O3—Si2—O4iii | 71.8 (2) | 71.2 (2) | 73.0 (2) |
O3—Si2—O4vi | 109.8 (4) | 98.3 (4) | 115.9 (4) |
O3iii—Si2—O3 | 117.2 (2) | 117.2 (2) | 117.2 (2) |
O3iii—Si2—O3iv | 151.5 (2) | 151.5 (2) | 151.5 (2) |
O3iii—Si2—O4 | 100.0 (3) | 100.0 (3) | 100.0 (3) |
O3iii—Si2—O4iii | 48.22 (17) | 48.22 (17) | 48.22 (17) |
O3iii—Si2—O4vi | 114.1 (3) | 114.1 (3) | 114.1 (3) |
O3iv—Si2—O3 | 43.5 (2) | 43.5 (2) | 43.5 (2) |
O3iv—Si2—O3iii | 151.5 (2) | 151.5 (2) | 151.5 (2) |
O3iv—Si2—O4 | 80.9 (4) | 80.9 (4) | 80.9 (4) |
O3iv—Si2—O4iii | 116.3 (2) | 116.3 (2) | 116.3 (2) |
O3iv—Si2—O4vi | 91.9 (4) | 91.9 (4) | 91.9 (4) |
O3v—Si2—O3 | 107.2 (3) | 104.9 (3) | 108.1 (3) |
O3v—Si2—O4 | 112.0 (4) | 108.4 (4) | 119.5 (4) |
O3v—Si2—O4iii | 35.7 (2) | 32.7 (2) | 37.0 (2) |
O3v—Si2—O4vi | 108.4 (4) | 104.3 (4) | 110.3 (4) |
O4—Si2—O4iii | 129.7 (3) | 122.2 (3) | 141.7 (3) |
O4—Si2—O4vi | 109.5 (4) | 108.7 (4) | 109.9 (4) |
O4vi—Si2—O4 | 109.5 (4) | 108.7 (4) | 109.9 (4) |
O4vi—Si2—O4iii | 117.0 (3) | 104.4 (3) | 124.1 (3) |
O1—Na1—O2 | 99.6 (3) | 95.9 (3) | 103.5 (3) |
O1—Na1—O2i | 62.9 (2) | 62.0 (2) | 63.6 (2) |
O1—Na1—O2vii | 97.3 (3) | 95.8 (3) | 98.9 (3) |
O1—Na1—O2ii | 133.3 (3) | 122.5 (3) | 143.7 (3) |
O2—Na1—O2i | 91.9 (3) | 91.2 (3) | 92.7 (3) |
O2—Na1—O2vii | 93.8 (3) | 93.6 (3) | 93.9 (3) |
O2—Na1—O2ii | 121.9 (3) | 113.0 (3) | 130.8 (3) |
O2i—Na1—O2 | 91.9 (3) | 91.2 (3) | 92.7 (3) |
O2i—Na1—O2vii | 160.0 (3) | 159.3 (3) | 160.7 (3) |
O2i—Na1—O2ii | 93.6 (3) | 92.3 (3) | 94.7 (3) |
O2vii—Na1—O2 | 93.8 (3) | 93.6 (3) | 93.9 (3) |
O2vii—Na1—O2i | 160.0 (3) | 159.3 (3) | 160.7 (3) |
O2vii—Na1—O2ii | 99.5 (3) | 98.6 (3) | 100.5 (3) |
O2ii—Na1—O2 | 121.9 (3) | 113.0 (3) | 130.8 (3) |
O2ii—Na1—O2i | 93.6 (3) | 92.3 (3) | 94.7 (3) |
O2ii—Na1—O2vii | 99.5 (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, x3−1/2, −x1/2; (vi) −x1, x2, −x3+1/2, x1/2; (vii) −x1+1/2, −x2+1/2, −x3+1, −x4; (viii) x1, −x2+1, x3−1/2, −x1/2. |
Experimental details
Crystal data |
Chemical formula | Na2O7Si3 |
Mr | 242.2 |
Crystal system, space group | Monoclinic, C2/c(0β0)s0† |
Temperature (K) | 298 |
Wave vectors | q = 0.56160b* |
a, b, c (Å) | 20.416 (6), 6.4987 (15), 4.9294 (19) |
β (°) | 90.26 (3) |
V (Å3) | 654.0 (4) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 0.85 |
Crystal size (mm) | 0.28 × 0.1 × 0.03 |
|
Data collection |
Diffractometer | STOE IPDS 2 diffractometer |
Absorption correction | – |
No. of measured, independent and observed [I > 3σ(I)] reflections | 4714, 1914, 1327 |
Rint | 0.082 |
(sin θ/λ)max (Å−1) | 0.632 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.073, 0.065, 2.30 |
No. of reflections | 1914 |
No. of parameters | 157 |
No. of restraints | ? |
Δρmax, Δρmin (e Å−3) | 1.07, −0.80 |
Selected geometric parameters (Å, º) top | Average | Minimum | Maximum |
Si1—O1i | 1.664 (8) | 1.603 (8) | 1.723 (8) |
Si1—O1ii | 1.628 (7) | 1.583 (7) | 1.665 (7) |
Si1—O2 | 1.575 (7) | 1.567 (7) | 1.582 (6) |
Si1—O4 | 1.615 (7) | 1.591 (7) | 1.642 (7) |
Si2—O3 | 1.608 (6) | 1.599 (6) | 1.633 (6) |
Si2—O3iii | 2.847 (6) | 2.847 (6) | 2.847 (6) |
Si2—O3iv | 2.236 (6) | 2.236 (6) | 2.236 (6) |
Si2—O3v | 1.607 (5) | 1.598 (5) | 1.631 (6) |
Si2—O4 | 1.594 (7) | 1.538 (8) | 1.641 (7) |
Si2—O4vi | 1.589 (8) | 1.563 (8) | 1.619 (8) |
Na1—O1 | 2.384 (7) | 2.339 (8) | 2.429 (8) |
Na1—O2 | 2.372 (7) | 2.328 (7) | 2.416 (7) |
Na1—O2i | 2.610 (8) | 2.579 (8) | 2.643 (9) |
Na1—O2vii | 2.395 (8) | 2.359 (9) | 2.430 (9) |
Na1—O2ii | 2.291 (7) | 2.256 (7) | 2.326 (7) |
| | | |
O1i—Si1—O1vii | 153.7 (3) | 152.5 (3) | 154.7 (3) |
O1i—Si1—O1ii | 105.3 (4) | 104.2 (4) | 106.5 (4) |
O1i—Si1—O2 | 107.5 (4) | 105.9 (4) | 109.3 (4) |
O1i—Si1—O4 | 107.6 (4) | 105.9 (4) | 109.5 (4) |
O1i—Si1—O4viii | 40.9 (3) | 39.0 (3) | 43.4 (3) |
O1ii—Si1—O1i | 105.3 (4) | 104.2 (4) | 106.5 (4) |
O1ii—Si1—O1vii | 48.9 (3) | 46.8 (3) | 50.6 (3) |
O1ii—Si1—O2 | 113.9 (4) | 112.0 (4) | 115.7 (4) |
O1ii—Si1—O4 | 108.2 (4) | 106.2 (4) | 110.2 (4) |
O1ii—Si1—O4viii | 78.5 (3) | 76.5 (3) | 81.2 (3) |
O2—Si1—O4 | 113.8 (4) | 110.5 (4) | 117.3 (4) |
O2—Si1—O4viii | 147.9 (3) | 144.6 (3) | 151.2 (3) |
O4—Si1—O4viii | 87.5 (3) | 86.3 (3) | 89.0 (3) |
O3—Si2—O3iii | 117.2 (2) | 117.2 (2) | 117.2 (2) |
O3—Si2—O3iv | 43.5 (2) | 43.5 (2) | 43.5 (2) |
O3—Si2—O3v | 107.2 (3) | 104.9 (3) | 108.1 (3) |
O3—Si2—O4 | 109.4 (4) | 104.3 (4) | 118.7 (4) |
O3—Si2—O4iii | 71.8 (2) | 71.2 (2) | 73.0 (2) |
O3—Si2—O4vi | 109.8 (4) | 98.3 (4) | 115.9 (4) |
O3iii—Si2—O3 | 117.2 (2) | 117.2 (2) | 117.2 (2) |
O3iii—Si2—O3iv | 151.5 (2) | 151.5 (2) | 151.5 (2) |
O3iii—Si2—O4 | 100.0 (3) | 100.0 (3) | 100.0 (3) |
O3iii—Si2—O4iii | 48.22 (17) | 48.22 (17) | 48.22 (17) |
O3iii—Si2—O4vi | 114.1 (3) | 114.1 (3) | 114.1 (3) |
O3iv—Si2—O3 | 43.5 (2) | 43.5 (2) | 43.5 (2) |
O3iv—Si2—O3iii | 151.5 (2) | 151.5 (2) | 151.5 (2) |
O3iv—Si2—O4 | 80.9 (4) | 80.9 (4) | 80.9 (4) |
O3iv—Si2—O4iii | 116.3 (2) | 116.3 (2) | 116.3 (2) |
O3iv—Si2—O4vi | 91.9 (4) | 91.9 (4) | 91.9 (4) |
O3v—Si2—O3 | 107.2 (3) | 104.9 (3) | 108.1 (3) |
O3v—Si2—O4 | 112.0 (4) | 108.4 (4) | 119.5 (4) |
O3v—Si2—O4iii | 35.7 (2) | 32.7 (2) | 37.0 (2) |
O3v—Si2—O4vi | 108.4 (4) | 104.3 (4) | 110.3 (4) |
O4—Si2—O4iii | 129.7 (3) | 122.2 (3) | 141.7 (3) |
O4—Si2—O4vi | 109.5 (4) | 108.7 (4) | 109.9 (4) |
O4vi—Si2—O4 | 109.5 (4) | 108.7 (4) | 109.9 (4) |
O4vi—Si2—O4iii | 117.0 (3) | 104.4 (3) | 124.1 (3) |
O1—Na1—O2 | 99.6 (3) | 95.9 (3) | 103.5 (3) |
O1—Na1—O2i | 62.9 (2) | 62.0 (2) | 63.6 (2) |
O1—Na1—O2vii | 97.3 (3) | 95.8 (3) | 98.9 (3) |
O1—Na1—O2ii | 133.3 (3) | 122.5 (3) | 143.7 (3) |
O2—Na1—O2i | 91.9 (3) | 91.2 (3) | 92.7 (3) |
O2—Na1—O2vii | 93.8 (3) | 93.6 (3) | 93.9 (3) |
O2—Na1—O2ii | 121.9 (3) | 113.0 (3) | 130.8 (3) |
O2i—Na1—O2 | 91.9 (3) | 91.2 (3) | 92.7 (3) |
O2i—Na1—O2vii | 160.0 (3) | 159.3 (3) | 160.7 (3) |
O2i—Na1—O2ii | 93.6 (3) | 92.3 (3) | 94.7 (3) |
O2vii—Na1—O2 | 93.8 (3) | 93.6 (3) | 93.9 (3) |
O2vii—Na1—O2i | 160.0 (3) | 159.3 (3) | 160.7 (3) |
O2vii—Na1—O2ii | 99.5 (3) | 98.6 (3) | 100.5 (3) |
O2ii—Na1—O2 | 121.9 (3) | 113.0 (3) | 130.8 (3) |
O2ii—Na1—O2i | 93.6 (3) | 92.3 (3) | 94.7 (3) |
O2ii—Na1—O2vii | 99.5 (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, x3−1/2, −x1/2; (vi) −x1, x2, −x3+1/2, x1/2; (vii) −x1+1/2, −x2+1/2, −x3+1, −x4; (viii) x1, −x2+1, x3−1/2, −x1/2. |