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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

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108768106041681/av5071sup1.cif
Contains datablocks global, datolite

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108768106041681/av5071sup2.hkl
Supplementary material

Computing details top

Data reduction: PROMETHEUS (Zucker et al., 1983); program(s) used to refine structure: MOLDOS96 (J. Protas, 1996).

Figures top
[Figure 1]
[Figure 2]
[Figure 3]
[Figure 4]
(datolite) top
Crystal data top
BCaHO5SiF(000) = 320
Mr = 159.99Dx = 2.988 Mg m3
Monoclinic, P21/aMo Kα radiation, λ = 0.71069 Å
Hall symbol: -P 2yabCell parameters from 15 reflections
a = 9.646 (6) Åθ = 6.0–12.8°
b = 7.620 (4) ŵ = 1.99 mm1
c = 4.839 (3) ÅT = 293 K
β = 90.14 (5)°Sphere, pale green
V = 355.7 (4) Å30.25 × 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 mARint = 0.026
Graphite monochromatorθmax = 50.1°, θmin = 7.0°
integrated intensities data fom θ/2θ scansh = 2020
Absorption correction: for a sphere
Zucker et al. (1983)
k = 1515
Tmin = ?, Tmax = ?l = 1010
6018 measured reflections1 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)] = 0.014Δρmax = 0.63 e Å3
wR(F2) = 0.019Δρmin = 0.36 e Å3
S = 1.04Extinction correction: Becker-Coppens type 1 isotropic
2583 reflectionsExtinction coefficient: 0.56 (2)
267 parameters
Crystal data top
BCaHO5SiV = 355.7 (4) Å3
Mr = 159.99Z = 4
Monoclinic, P21/aMo Kα radiation
a = 9.646 (6) ŵ = 1.99 mm1
b = 7.620 (4) ÅT = 293 K
c = 4.839 (3) Å0.25 × 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)] = 0.014267 parameters
wR(F2) = 0.019Δρmax = 0.63 e Å3
S = 1.04Δρmin = 0.36 e Å3
2583 reflections
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
H0.5840.5520.8290.036 (7)*
B0.34077 (5)0.41057 (6)0.56786 (10)0.0054 (3)
Ca0.33610 (1)0.10613 (1)0.99161 (2)0.00639 (5)
O10.03739 (5)0.40109 (6)0.24048 (9)0.0074 (2)
O20.45730 (4)0.30115 (5)0.67017 (8)0.0063 (2)
O30.21047 (4)0.33474 (6)0.67514 (8)0.0063 (2)
O40.14598 (5)0.08787 (5)0.31499 (9)0.0070 (2)
O50.33680 (5)0.41344 (6)0.25851 (9)0.0073 (2)
Si0.08438 (1)0.26617 (2)0.46891 (3)0.00425 (9)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
B0.00482 (14)0.00566 (15)0.00583 (14)0.00014 (12)0.00031 (12)0.00006 (11)
Ca0.00589 (3)0.00680 (3)0.00647 (3)0.00007 (2)0.00041 (2)0.00047 (2)
O10.00735 (13)0.00702 (12)0.00792 (12)0.00029 (11)0.00136 (11)0.00287 (10)
O20.00488 (12)0.00751 (13)0.00637 (12)0.00201 (10)0.00101 (9)0.00095 (10)
O30.00451 (11)0.00832 (13)0.00601 (12)0.00182 (10)0.00005 (9)0.00027 (10)
O40.00888 (14)0.00427 (12)0.00798 (12)0.00083 (10)0.00233 (11)0.00022 (9)
O50.00700 (13)0.00978 (14)0.00509 (11)0.00055 (11)0.00020 (10)0.00063 (10)
Si0.00371 (5)0.00411 (5)0.00492 (5)0.00028 (3)0.00006 (3)0.00032 (3)
Geometric parameters (Å, º) top
Si—O11.5754 (11)Ca—O1iv2.2830 (15)
Si—O2i1.6493 (11)Ca—O22.4502 (16)
Si—O31.6560 (11)Ca—O3v2.6613 (17)
Si—O41.6601 (11)Ca—O32.6152 (17)
B—O21.4836 (11)Ca—O4vi2.4177 (16)
B—O31.4786 (11)Ca—O5iii2.5283 (16)
B—O4ii1.4706 (11)Ca—O5vi2.6743 (17)
B—O51.4975 (11)O5—Hvii0.9100
Ca—O1iii2.2800 (15)
O1—Si—O2i113.85 (5)O1iv—Ca—O3v78.83 (5)
O1—Si—O3115.25 (6)O1iv—Ca—O3135.83 (5)
O1—Si—O4108.78 (6)O1iv—Ca—O4vi107.62 (5)
O2i—Si—O3106.75 (5)O1iv—Ca—O5iii142.91 (5)
O2i—Si—O4106.13 (5)O1iv—Ca—O5vi76.42 (5)
O3—Si—O4105.39 (5)O2—Ca—O3v159.63 (5)
O2—B—O3107.89 (6)O2—Ca—O356.32 (5)
O2—B—O4ii108.82 (6)O2—Ca—O4vi144.06 (5)
O2—B—O5111.06 (6)O2—Ca—O5iii111.32 (5)
O3—B—O4ii107.27 (6)O2—Ca—O5vi76.99 (5)
O3—B—O5109.69 (6)O3v—Ca—O3142.54 (5)
O4ii—B—O5111.96 (6)O3v—Ca—O4vi55.50 (5)
O1iii—Ca—O1iv77.75 (5)O3v—Ca—O5iii74.14 (5)
O1iii—Ca—O281.15 (5)O3v—Ca—O5vi112.83 (5)
O1iii—Ca—O3v81.80 (5)O3—Ca—O4vi93.80 (5)
O1iii—Ca—O3114.57 (5)O3—Ca—O5iii78.60 (5)
O1iii—Ca—O4vi133.40 (5)O3—Ca—O5vi72.55 (5)
O1iii—Ca—O5iii73.71 (5)O4vi—Ca—O5iii77.05 (5)
O1iii—Ca—O5vi146.85 (5)O4vi—Ca—O5vi74.86 (5)
O1iv—Ca—O286.73 (5)O5iii—Ca—O5vi137.78 (5)
Symmetry codes: (i) x1/2, y+1/2, z; (ii) x+1/2, y+1/2, z+1; (iii) x+1/2, y1/2, z+1; (iv) x+1/2, y+1/2, z+1; (v) x+1/2, y1/2, z+2; (vi) x, y, z+1; (vii) x+1, y+1, z+1.

Experimental details

Crystal data
Chemical formulaBCaHO5Si
Mr159.99
Crystal system, space groupMonoclinic, P21/a
Temperature (K)293
a, b, c (Å)9.646 (6), 7.620 (4), 4.839 (3)
β (°) 90.14 (5)
V3)355.7 (4)
Z4
Radiation typeMo Kα
µ (mm1)1.99
Crystal size (mm)0.25 × 0.25 × 0.25 × 0.13 (radius)
Data collection
DiffractometerFour-circle
diffractometer
Absorption correctionFor a sphere
Zucker et al. (1983)
No. of measured, independent and
observed [I > 1.96u(I)] reflections
6018, 2584, 2584
Rint0.026
(sin θ/λ)max1)1.079
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.014, 0.019, 1.04
No. of reflections2583
No. of parameters267
No. of restraints?
Δρmax, Δρmin (e Å3)0.63, 0.36

Computer programs: PROMETHEUS (Zucker et al., 1983), MOLDOS96 (J. Protas, 1996).

Selected bond lengths (Å) top
Si—O11.5754 (11)Ca—O1iv2.2830 (15)
Si—O2i1.6493 (11)Ca—O22.4502 (16)
Si—O31.6560 (11)Ca—O3v2.6613 (17)
Si—O41.6601 (11)Ca—O32.6152 (17)
B—O21.4836 (11)Ca—O4vi2.4177 (16)
B—O31.4786 (11)Ca—O5iii2.5283 (16)
B—O4ii1.4706 (11)Ca—O5vi2.6743 (17)
B—O51.4975 (11)O5—Hvii0.9100
Ca—O1iii2.2800 (15)
Symmetry codes: (i) x1/2, y+1/2, z; (ii) x+1/2, y+1/2, z+1; (iii) x+1/2, y1/2, z+1; (iv) x+1/2, y+1/2, z+1; (v) x+1/2, y1/2, z+2; (vi) x, y, z+1; (vii) x+1, y+1, z+1.
 

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