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
Key indicators
- Powder neutron study
- T = 295 K
- Mean (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
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)2 | Z = 4 |
Mr = 182.07 | Dx = 3.396 Mg m−3 |
Orthorhombic, Pbnm | Neutron radiation, λ = 1.37404 Å |
a = 4.7282 (1) Å | T = 295 K |
b = 8.9320 (2) Å | Particle morphology: equii-dimensional 10µm crystals |
c = 8.4309 (2) Å | white |
V = 356.06 (1) Å3 | cylinder, 4 × 4 mm |
Data collection top
The PSD powder diffractometer D20, at ILL | Data collection mode: reflection |
Germanium monochromator | Scan method: step |
Specimen mounting: loose powder in can | 2θmin = 15.018°, 2θmax = 154.012°, 2θstep = 0.025° |
Refinement top
Least-squares matrix: full | 52 parameters |
Rp = 0.037 | 0 restraints |
Rwp = 0.046 | 0 constraints |
Rexp = 0.035 | |
R(F2) = 0.07382 | (Δ/σ)max = 0.01 |
5960 data points | Background 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 °/2θ | Preferred 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 | x | y | z | Uiso*/Ueq | Occ. (<1) |
Al | 0.9071 (6) | 0.1325 (3) | 0.0779 (3) | 0.0030 (4) | |
Si | 0.4032 (6) | 0.9404 (3) | 0.25 | 0.0002 (5) | |
O1 | 0.7080 (5) | 0.0260 (2) | 0.25 | 0.0015 (4) | |
O2 | 0.4431 (4) | 0.7551 (3) | 0.25 | 0.0017 (5) | |
O3 | 0.2129 (3) | 0.9922 (2) | 0.0946 (2) | 0.0031 (3) | |
O4 | 0.5917 (3) | 0.2504 (2) | 0.0661 (2) | 0.0048 (3) | |
D1 | 0.440 (1) | 0.1858 (5) | 0.1031 (8) | 0.045 (1) | 0.5 |
D2 | 0.532 (1) | 0.2811 (7) | 0.1675 (6) | 0.048 (1) | 0.5 |
Geometric parameters (Å, º) top
Al—O1 | 1.974 (3) | Si—O1v | 1.631 (4) |
Al—O2i | 1.951 (3) | Si—O2 | 1.666 (4) |
Al—O3ii | 1.918 (3) | Si—O3 | 1.656 (3) |
Al—O3iii | 1.917 (3) | Si—O3vi | 1.656 (3) |
Al—O4 | 1.829 (3) | D1—O4 | 0.971 (5) |
Al—O4iv | 1.825 (3) | D2—O4 | 0.941 (5) |
| | | |
Al—O4—D1 | 104.0 (3) | Alvii—O4—D1 | 101.7 (4) |
Al—O4—D2 | 111.3 (4) | Alvii—O4—D2 | 107.1 (4) |
Symmetry codes: (i) −x+3/2, y−1/2, z; (ii) x+1, y−1, 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) x−1/2, −y+1/2, −z. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
O4—D1···O4vii | 0.97 (1) | 2.25 (1) | 2.614 (2) | 101 (1) |
O4—D1···O2viii | 0.97 (1) | 2.28 (1) | 2.966 (2) | 127 (1) |
O4—D1···O3ix | 0.97 (1) | 2.04 (1) | 2.930 (2) | 152 (1) |
O4—D2···O1 | 0.94 (1) | 2.52 (1) | 2.593 (2) | 84 (1) |
O4—D2···O2viii | 0.94 (1) | 2.36 (1) | 2.966 (2) | 122 (1) |
O4—D2···O4vi | 0.94 (1) | 2.28 (1) | 3.101 (2) | 145 (1) |
Symmetry codes: (vi) x, y, −z+1/2; (vii) x−1/2, −y+1/2, −z; (viii) −x+1/2, y−1/2, −z+1/2; (ix) x, y−1, z. |