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The structure of topaz-OD, dialuminium orthosilicate di­hydro­xide, Al2SiO4(OD)2, was refined in the space group Pbnm by Rietveld analysis of constant wavelength neutron powder diffraction data. Two non-equivalent half-occupied deuterium positions were located. Each D atom is characterized by an irregular trifurcated hydrogen-bond geometry. The refined hydrogen-bond distances are in the ranges 2.038 (5)-2.281 (6) and 2.280 (5)-2.524 (6) Å for the two D atoms. Hydro­gen-bond angles range from 83.6 (4) to 151.9 (4)°. Results indicate that it is feasible to characterize the hydrogen bonding in small-volume samples (25 mg) synthesized at high pressure and temperature.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536805034811/wm6096sup1.cif
Contains datablocks global, I

rtv

Rietveld powder data file (CIF format) https://doi.org/10.1107/S1600536805034811/wm6096Isup2.rtv
Contains datablock I

Key indicators

  • Powder neutron study
  • T = 295 K
  • Mean [sigma](Al-O) = 0.003 Å
  • R factor = 0.037
  • wR factor = 0.046
  • Data-to-parameter ratio = 106.9

checkCIF/PLATON results

No syntax errors found



Alert level A REFI001_ALERT_1_A _refine_ls_structure_factor_coef is missing The structure factor coefficient should be one of the following * Inet * Fsqd * F The following tests will not be performed FCOEF_01 PLAT025_ALERT_1_A Hmin..Lmax Data Incomplete or Missing .......... ? PLAT050_ALERT_1_A Absorption Coefficient mu Missing .............. ?
Alert level B Crystal system given = orthorhombic PLAT482_ALERT_4_B Small D-H..A Angle Rep for O4 .. O1 .. 83.60 Deg.
Alert level C PLAT128_ALERT_4_C Non-standard setting of Space group Pnma .... Pbnm
3 ALERT level A = In general: serious problem 1 ALERT level B = Potentially serious problem 1 ALERT level C = Check and explain 0 ALERT level G = General alerts; check 3 ALERT type 1 CIF construction/syntax error, inconsistent or missing data 0 ALERT type 2 Indicator that the structure model may be wrong or deficient 0 ALERT type 3 Indicator that the structure quality may be low 2 ALERT type 4 Improvement, methodology, query or suggestion

Computing details top

Data collection: MAD (Local program in D20 diffractometer); cell refinement: GSAS (Larson & Von Dreele, 2000); data reduction: LAMP (Richard et al., 2004); program(s) used to refine structure: GSAS (Larson & Von Dreele, 2000); molecular graphics: Diamond (Brandenburg, 2005); software used to prepare material for publication: GSAS (Larson & Von Dreele, 2000).

Dialuminium orthosilicate dihydroxide top
Crystal data top
Al2SiO4(OD)2Z = 4
Mr = 182.07Dx = 3.396 Mg m3
Orthorhombic, PbnmNeutron radiation, λ = 1.37404 Å
a = 4.7282 (1) ÅT = 295 K
b = 8.9320 (2) ÅParticle morphology: equii-dimensional 10µm crystals
c = 8.4309 (2) Åwhite
V = 356.06 (1) Å3cylinder, 4 × 4 mm
Data collection top
The PSD powder
diffractometer D20, at ILL
Data collection mode: reflection
Germanium monochromatorScan method: step
Specimen mounting: loose powder in can2θmin = 15.018°, 2θmax = 154.012°, 2θstep = 0.025°
Refinement top
Least-squares matrix: full52 parameters
Rp = 0.0370 restraints
Rwp = 0.0460 constraints
Rexp = 0.035
R(F2) = 0.07382(Δ/σ)max = 0.01
5960 data pointsBackground function: GSAS Background function number 1 with 12 terms. Shifted Chebyshev function of 1st kind 1: 15.5910 2: -1.30168 3: 1.59919 4: 1.754620E-02 5: -0.429047 6: -0.549426 7: 0.155696 8: 2.576300E-02 9: 0.372468 10: -0.107973 11: -0.172470 12: -0.149335
Excluded region(s): <15.0 °/2θPreferred orientation correction: none
Profile function: CW Profile function number 2 with 18 terms Profile coefficients for Simpson's rule integration of pseudovoigt function (Howard, 1982; Thompson et al., 1987). #1(GU) = 217.007 #2(GV) = -511.054 #3(GW) = 407.749 #4(LX) = 2.951 #5(LY) = 0.000 #6(trns) = 7.080 #7(asym) = 18.0696 #8(shft) = 0.0000 #9(GP) = 0.000 #10(stec)= 0.00 #11(ptec)= 0.00 #12(sfec)= 0.00 #13(L11) = 0.000 #14(L22) = 0.000 #15(L33) = 0.000 #16(L12) = 0.000 #17(L13) = 0.000 #18(L23) = 0.000 Peak tails are ignored where the intensity is below 0.0010 times the peak Aniso. broadening axis 0.0 0.0 1.0
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/UeqOcc. (<1)
Al0.9071 (6)0.1325 (3)0.0779 (3)0.0030 (4)
Si0.4032 (6)0.9404 (3)0.250.0002 (5)
O10.7080 (5)0.0260 (2)0.250.0015 (4)
O20.4431 (4)0.7551 (3)0.250.0017 (5)
O30.2129 (3)0.9922 (2)0.0946 (2)0.0031 (3)
O40.5917 (3)0.2504 (2)0.0661 (2)0.0048 (3)
D10.440 (1)0.1858 (5)0.1031 (8)0.045 (1)0.5
D20.532 (1)0.2811 (7)0.1675 (6)0.048 (1)0.5
Geometric parameters (Å, º) top
Al—O11.974 (3)Si—O1v1.631 (4)
Al—O2i1.951 (3)Si—O21.666 (4)
Al—O3ii1.918 (3)Si—O31.656 (3)
Al—O3iii1.917 (3)Si—O3vi1.656 (3)
Al—O41.829 (3)D1—O40.971 (5)
Al—O4iv1.825 (3)D2—O40.941 (5)
Al—O4—D1104.0 (3)Alvii—O4—D1101.7 (4)
Al—O4—D2111.3 (4)Alvii—O4—D2107.1 (4)
Symmetry codes: (i) x+3/2, y1/2, z; (ii) x+1, y1, z; (iii) x+1, y+1, z; (iv) x+1/2, y+1/2, z; (v) x, y+1, z; (vi) x, y, z+1/2; (vii) x1/2, y+1/2, z.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O4—D1···O4vii0.97 (1)2.25 (1)2.614 (2)101 (1)
O4—D1···O2viii0.97 (1)2.28 (1)2.966 (2)127 (1)
O4—D1···O3ix0.97 (1)2.04 (1)2.930 (2)152 (1)
O4—D2···O10.94 (1)2.52 (1)2.593 (2)84 (1)
O4—D2···O2viii0.94 (1)2.36 (1)2.966 (2)122 (1)
O4—D2···O4vi0.94 (1)2.28 (1)3.101 (2)145 (1)
Symmetry codes: (vi) x, y, z+1/2; (vii) x1/2, y+1/2, z; (viii) x+1/2, y1/2, z+1/2; (ix) x, y1, z.
 

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