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The electron density distribution in the layer silicate datolite, Ca[BOH(SiO4)], was analyzed using high-precision single-crystal X-ray diffraction data (Mo Kα, T = 293 K). The Hansen–Coppens multipole model and Bader's topological analysis of the electron density provides a basis for the quantitative characterization of the bonded interaction of datolite. The results are presented both in the form of maps of the electron density distribution and its Laplacian, and in a compact way in terms of the critical points of the electron density. The relative electronegativities are also discussed. It was shown that closed-shell type interactions exist between Ca and O atoms, whereas Si—O and B—O bonds exhibit an intermediate nature with a strong covalent component. An analysis of the topology of the electrostatic potential demonstrates the relevance of considering this physical property to obtain a complete picture of structure-forming factors.
Supporting information
Data reduction: PROMETHEUS (Zucker et al., 1983); program(s) used to refine structure: MOLDOS96 (J. Protas, 1996).
Crystal data top
BCaHO5Si | F(000) = 320 |
Mr = 159.99 | Dx = 2.988 Mg m−3 |
Monoclinic, P21/a | Mo Kα radiation, λ = 0.71069 Å |
Hall symbol: -P 2yab | Cell parameters from 15 reflections |
a = 9.646 (6) Å | θ = 6.0–12.8° |
b = 7.620 (4) Å | µ = 1.99 mm−1 |
c = 4.839 (3) Å | T = 293 K |
β = 90.14 (5)° | Sphere, pale green |
V = 355.7 (4) Å3 | 0.25 × 0.25 × 0.25 × 0.13 (radius) mm |
Z = 4 | |
Data collection top
Four-circle diffractometer | 2584 reflections with I > 1.96u(I) |
Radiation source: Normal focus Mo-X-ray 40kV-20 mA | Rint = 0.026 |
Graphite monochromator | θmax = 50.1°, θmin = 7.0° |
integrated intensities data fom θ/2θ scans | h = −20→20 |
Absorption correction: for a sphere Zucker et al. (1983) | k = −15→15 |
Tmin = ?, Tmax = ? | l = −10→10 |
6018 measured reflections | 1 standard reflections every 100 reflections |
2584 independent reflections | intensity decay: no decay, variation 2% |
Refinement top
Refinement on F | w = 1/(s**2 + 0.000225F**2) |
Least-squares matrix: full | (Δ/σ)max < 0.001 |
R[F2 > 2σ(F2)] = 0.014 | Δρmax = 0.63 e Å−3 |
wR(F2) = 0.019 | Δρmin = −0.36 e Å−3 |
S = 1.04 | Extinction correction: Becker-Coppens type 1 isotropic |
2583 reflections | Extinction coefficient: 0.56 (2) |
267 parameters | |
Crystal data top
BCaHO5Si | V = 355.7 (4) Å3 |
Mr = 159.99 | Z = 4 |
Monoclinic, P21/a | Mo Kα radiation |
a = 9.646 (6) Å | µ = 1.99 mm−1 |
b = 7.620 (4) Å | T = 293 K |
c = 4.839 (3) Å | 0.25 × 0.25 × 0.25 × 0.13 (radius) mm |
β = 90.14 (5)° | |
Data collection top
Four-circle diffractometer | 2584 reflections with I > 1.96u(I) |
Absorption correction: for a sphere Zucker et al. (1983) | Rint = 0.026 |
Tmin = ?, Tmax = ? | 1 standard reflections every 100 reflections |
6018 measured reflections | intensity decay: no decay, variation 2% |
2584 independent reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.014 | 267 parameters |
wR(F2) = 0.019 | Δρmax = 0.63 e Å−3 |
S = 1.04 | Δρmin = −0.36 e Å−3 |
2583 reflections | |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | |
H | 0.584 | 0.552 | 0.829 | 0.036 (7)* | |
B | 0.34077 (5) | 0.41057 (6) | 0.56786 (10) | 0.0054 (3) | |
Ca | 0.33610 (1) | 0.10613 (1) | 0.99161 (2) | 0.00639 (5) | |
O1 | 0.03739 (5) | 0.40109 (6) | 0.24048 (9) | 0.0074 (2) | |
O2 | 0.45730 (4) | 0.30115 (5) | 0.67017 (8) | 0.0063 (2) | |
O3 | 0.21047 (4) | 0.33474 (6) | 0.67514 (8) | 0.0063 (2) | |
O4 | 0.14598 (5) | 0.08787 (5) | 0.31499 (9) | 0.0070 (2) | |
O5 | 0.33680 (5) | 0.41344 (6) | 0.25851 (9) | 0.0073 (2) | |
Si | 0.08438 (1) | 0.26617 (2) | 0.46891 (3) | 0.00425 (9) | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
B | 0.00482 (14) | 0.00566 (15) | 0.00583 (14) | −0.00014 (12) | 0.00031 (12) | −0.00006 (11) |
Ca | 0.00589 (3) | 0.00680 (3) | 0.00647 (3) | −0.00007 (2) | 0.00041 (2) | −0.00047 (2) |
O1 | 0.00735 (13) | 0.00702 (12) | 0.00792 (12) | −0.00029 (11) | −0.00136 (11) | 0.00287 (10) |
O2 | 0.00488 (12) | 0.00751 (13) | 0.00637 (12) | 0.00201 (10) | 0.00101 (9) | 0.00095 (10) |
O3 | 0.00451 (11) | 0.00832 (13) | 0.00601 (12) | −0.00182 (10) | −0.00005 (9) | 0.00027 (10) |
O4 | 0.00888 (14) | 0.00427 (12) | 0.00798 (12) | 0.00083 (10) | 0.00233 (11) | 0.00022 (9) |
O5 | 0.00700 (13) | 0.00978 (14) | 0.00509 (11) | −0.00055 (11) | 0.00020 (10) | 0.00063 (10) |
Si | 0.00371 (5) | 0.00411 (5) | 0.00492 (5) | −0.00028 (3) | 0.00006 (3) | 0.00032 (3) |
Geometric parameters (Å, º) top
Si—O1 | 1.5754 (11) | Ca—O1iv | 2.2830 (15) |
Si—O2i | 1.6493 (11) | Ca—O2 | 2.4502 (16) |
Si—O3 | 1.6560 (11) | Ca—O3v | 2.6613 (17) |
Si—O4 | 1.6601 (11) | Ca—O3 | 2.6152 (17) |
B—O2 | 1.4836 (11) | Ca—O4vi | 2.4177 (16) |
B—O3 | 1.4786 (11) | Ca—O5iii | 2.5283 (16) |
B—O4ii | 1.4706 (11) | Ca—O5vi | 2.6743 (17) |
B—O5 | 1.4975 (11) | O5—Hvii | 0.9100 |
Ca—O1iii | 2.2800 (15) | | |
| | | |
O1—Si—O2i | 113.85 (5) | O1iv—Ca—O3v | 78.83 (5) |
O1—Si—O3 | 115.25 (6) | O1iv—Ca—O3 | 135.83 (5) |
O1—Si—O4 | 108.78 (6) | O1iv—Ca—O4vi | 107.62 (5) |
O2i—Si—O3 | 106.75 (5) | O1iv—Ca—O5iii | 142.91 (5) |
O2i—Si—O4 | 106.13 (5) | O1iv—Ca—O5vi | 76.42 (5) |
O3—Si—O4 | 105.39 (5) | O2—Ca—O3v | 159.63 (5) |
O2—B—O3 | 107.89 (6) | O2—Ca—O3 | 56.32 (5) |
O2—B—O4ii | 108.82 (6) | O2—Ca—O4vi | 144.06 (5) |
O2—B—O5 | 111.06 (6) | O2—Ca—O5iii | 111.32 (5) |
O3—B—O4ii | 107.27 (6) | O2—Ca—O5vi | 76.99 (5) |
O3—B—O5 | 109.69 (6) | O3v—Ca—O3 | 142.54 (5) |
O4ii—B—O5 | 111.96 (6) | O3v—Ca—O4vi | 55.50 (5) |
O1iii—Ca—O1iv | 77.75 (5) | O3v—Ca—O5iii | 74.14 (5) |
O1iii—Ca—O2 | 81.15 (5) | O3v—Ca—O5vi | 112.83 (5) |
O1iii—Ca—O3v | 81.80 (5) | O3—Ca—O4vi | 93.80 (5) |
O1iii—Ca—O3 | 114.57 (5) | O3—Ca—O5iii | 78.60 (5) |
O1iii—Ca—O4vi | 133.40 (5) | O3—Ca—O5vi | 72.55 (5) |
O1iii—Ca—O5iii | 73.71 (5) | O4vi—Ca—O5iii | 77.05 (5) |
O1iii—Ca—O5vi | 146.85 (5) | O4vi—Ca—O5vi | 74.86 (5) |
O1iv—Ca—O2 | 86.73 (5) | O5iii—Ca—O5vi | 137.78 (5) |
Symmetry codes: (i) x−1/2, −y+1/2, z; (ii) −x+1/2, y+1/2, −z+1; (iii) −x+1/2, y−1/2, −z+1; (iv) x+1/2, −y+1/2, z+1; (v) −x+1/2, y−1/2, −z+2; (vi) x, y, z+1; (vii) −x+1, −y+1, −z+1. |
Experimental details
Crystal data |
Chemical formula | BCaHO5Si |
Mr | 159.99 |
Crystal system, space group | Monoclinic, P21/a |
Temperature (K) | 293 |
a, b, c (Å) | 9.646 (6), 7.620 (4), 4.839 (3) |
β (°) | 90.14 (5) |
V (Å3) | 355.7 (4) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 1.99 |
Crystal size (mm) | 0.25 × 0.25 × 0.25 × 0.13 (radius) |
|
Data collection |
Diffractometer | Four-circle diffractometer |
Absorption correction | For a sphere Zucker et al. (1983) |
No. of measured, independent and observed [I > 1.96u(I)] reflections | 6018, 2584, 2584 |
Rint | 0.026 |
(sin θ/λ)max (Å−1) | 1.079 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.014, 0.019, 1.04 |
No. of reflections | 2583 |
No. of parameters | 267 |
No. of restraints | ? |
Δρmax, Δρmin (e Å−3) | 0.63, −0.36 |
Selected bond lengths (Å) topSi—O1 | 1.5754 (11) | Ca—O1iv | 2.2830 (15) |
Si—O2i | 1.6493 (11) | Ca—O2 | 2.4502 (16) |
Si—O3 | 1.6560 (11) | Ca—O3v | 2.6613 (17) |
Si—O4 | 1.6601 (11) | Ca—O3 | 2.6152 (17) |
B—O2 | 1.4836 (11) | Ca—O4vi | 2.4177 (16) |
B—O3 | 1.4786 (11) | Ca—O5iii | 2.5283 (16) |
B—O4ii | 1.4706 (11) | Ca—O5vi | 2.6743 (17) |
B—O5 | 1.4975 (11) | O5—Hvii | 0.9100 |
Ca—O1iii | 2.2800 (15) | | |
Symmetry codes: (i) x−1/2, −y+1/2, z; (ii) −x+1/2, y+1/2, −z+1; (iii) −x+1/2, y−1/2, −z+1; (iv) x+1/2, −y+1/2, z+1; (v) −x+1/2, y−1/2, −z+2; (vi) x, y, z+1; (vii) −x+1, −y+1, −z+1. |
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