Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270102023053/fg1678sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270102023053/fg1678Isup2.hkl | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270102023053/fg1678IIsup3.hkl |
Both compositions were by-products of melts containing barium. For composition (I) (x = 1/5), a powder sample of Ba2LaV3O11 was prepared by solid-state reaction; reagents used were BaCO3, La2O3 (both 99%; BDH Chemicals Ltd, Poole, England) and V2O5 (99.2%; Johnson Matthey, Royston, England). La2O3 was dried at 1173 K prior to use, and BaCO3 and V2O5 were both dried at 573 K. Single crystals were grown by the method of Huang et al. (1994). The powder was melted at 1573 K and held at this temperature for 30 min. The temperature was then decreased at a rate of 1 K min−1 to 1523 K, whereupon it was increased again to 1573 K in steps of 2 K min−1. This was repeated three times in order to obtain, after cooling to room temperature, crystals of (I) suitable for analysis. For composition (II) (x = 0.06), the single-crystal was accidentally grown during the study of the ternary phase diagram BaO-Li2O-TiO2 (Suckut, 1991). The target phase was in the range 10–18 mol% BaO, 12–16 mol% Li2O and 72–77 mol% TiO2, with an idealized formula of BaLi2Ti6O14. The starting reagents were BaCO3 (99.5%; May & Baker Ltd, Dagenham, England), TiO2 (99.9%; Aldrich, USA) and Li2CO3 (99%; FSA Laboratory Supplies, Loughborough, England). The composition 72 mol% TiO2, 16.5 mol% Li2O and 11.5 mol% BaO was used in an attempt to grow single crystals of the desired phase. The melting point of this composition was found to be 1533 K; the powder was heated to 10 K below the melting point and cooled at 0.5 K min−1 to 30 K below the melting point. It was then heated to 15 K below the melting point and finally cooled to room temperature. In both cases, the powder was placed in a platinum envelope in an aluminosilicate crucible. BaO is well known as a good fluxing agent in the growth of single crystals, and clearly has brought about escape of the Ba-containing melt from the envelope and reaction with the aluminosilicate crucible, to give the barium aluminosilicate phases described above. Thus, in addition to providing information on barium-deficient celsian phases, this constitutes a warning for solid-state chemists.
Anisotropic displacement parameters were refined for all atoms. Al/Si and Ba site occupancies were refined, but constrained so as to ensure charge balance, while assuming full occupancy but complete disorder of the Al/Si sites.
Data collection: SMART (Bruker, 1998) for (I); P3 software (Nicolet, 1980) for (II). Cell refinement: SAINT (Bruker, 2000) for (I); P3 software for (II). Data reduction: SAINT for (I); RDNIC (Howie, 1980) for (II). For both compounds, program(s) used to solve structure: SHELXS86 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997). Molecular graphics: ORTEX in OSCAIL (McArdle, 1994, 2000) and ATOMS (Dowty, 1999) for (I). For both compounds, software used to prepare material for publication: SHELXL97.
Al1.60Ba0.80O8Si2.40 | F(000) = 652 |
Mr = 348.12 | Dx = 3.159 Mg m−3 |
Monoclinic, C2/m | Mo Kα radiation, λ = 0.71073 Å |
a = 8.6090 (8) Å | Cell parameters from 2197 reflections |
b = 13.0658 (12) Å | θ = 4.8–32.4° |
c = 7.2047 (7) Å | µ = 4.96 mm−1 |
β = 115.418 (2)° | T = 292 K |
V = 731.96 (12) Å3 | Block, colourless |
Z = 4 | 0.20 × 0.18 × 0.14 mm |
Bruker SMART 1000 CCD area-detector diffractometer | 1366 independent reflections |
Radiation source: fine-focus sealed tube | 1223 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.022 |
ϕ/ω scans | θmax = 32.5°, θmin = 3.1° |
Absorption correction: multi-scan (SADABS; Bruker, 2000) | h = −12→13 |
Tmin = 0.349, Tmax = 0.500 | k = −16→19 |
3542 measured reflections | l = −10→7 |
Refinement on F2 | 0 restraints |
Least-squares matrix: full | Primary atom site location: heavy-atom method |
R[F2 > 2σ(F2)] = 0.022 | Secondary atom site location: difference Fourier map |
wR(F2) = 0.056 | w = 1/[σ2(Fo2) + (0.0302P)2] where P = (Fo2 + 2Fc2)/3 |
S = 1.07 | (Δ/σ)max < 0.001 |
1366 reflections | Δρmax = 0.73 e Å−3 |
64 parameters | Δρmin = −0.82 e Å−3 |
Al1.60Ba0.80O8Si2.40 | V = 731.96 (12) Å3 |
Mr = 348.12 | Z = 4 |
Monoclinic, C2/m | Mo Kα radiation |
a = 8.6090 (8) Å | µ = 4.96 mm−1 |
b = 13.0658 (12) Å | T = 292 K |
c = 7.2047 (7) Å | 0.20 × 0.18 × 0.14 mm |
β = 115.418 (2)° |
Bruker SMART 1000 CCD area-detector diffractometer | 1366 independent reflections |
Absorption correction: multi-scan (SADABS; Bruker, 2000) | 1223 reflections with I > 2σ(I) |
Tmin = 0.349, Tmax = 0.500 | Rint = 0.022 |
3542 measured reflections |
R[F2 > 2σ(F2)] = 0.022 | 64 parameters |
wR(F2) = 0.056 | 0 restraints |
S = 1.07 | Δρmax = 0.73 e Å−3 |
1366 reflections | Δρmin = −0.82 e Å−3 |
Experimental. Intensity data, in terms of the reflections allowed by C-centring, are in fact 99.0% complete. |
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. |
Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger. |
x | y | z | Uiso*/Ueq | Occ. (<1) | |
Ba1 | 0.28318 (3) | 0.0000 | 0.13152 (4) | 0.01796 (8) | 0.7976 (14) |
Al1 | 0.00846 (7) | 0.18359 (4) | 0.22433 (8) | 0.01116 (13) | 0.3988 (7) |
Si1 | 0.00846 (7) | 0.18359 (4) | 0.22433 (8) | 0.01116 (13) | 0.6012 (7) |
Al2 | 0.20494 (7) | 0.38160 (4) | 0.34646 (8) | 0.01057 (13) | 0.3988 (7) |
Si2 | 0.20494 (7) | 0.38160 (4) | 0.34646 (8) | 0.01057 (13) | 0.6012 (7) |
O1 | 0.0000 | 0.14056 (16) | 0.0000 | 0.0175 (4) | |
O2 | 0.1254 (3) | 0.5000 | 0.2877 (4) | 0.0193 (4) | |
O3 | 0.3272 (2) | 0.36019 (13) | 0.2256 (3) | 0.0233 (3) | |
O4 | 0.0273 (2) | 0.31038 (12) | 0.2538 (3) | 0.0203 (3) | |
O5 | 0.1850 (2) | 0.12649 (13) | 0.4000 (2) | 0.0212 (3) |
U11 | U22 | U33 | U12 | U13 | U23 | |
Ba1 | 0.01254 (11) | 0.02096 (12) | 0.01868 (12) | 0.000 | 0.00509 (8) | 0.000 |
Al1 | 0.0109 (2) | 0.0127 (2) | 0.0102 (3) | −0.00217 (18) | 0.0049 (2) | −0.00089 (19) |
Si1 | 0.0109 (2) | 0.0127 (2) | 0.0102 (3) | −0.00217 (18) | 0.0049 (2) | −0.00089 (19) |
Al2 | 0.0103 (2) | 0.0106 (2) | 0.0108 (3) | −0.00013 (17) | 0.0046 (2) | −0.00002 (18) |
Si2 | 0.0103 (2) | 0.0106 (2) | 0.0108 (3) | −0.00013 (17) | 0.0046 (2) | −0.00002 (18) |
O1 | 0.0206 (10) | 0.0215 (10) | 0.0124 (10) | 0.000 | 0.0090 (8) | 0.000 |
O2 | 0.0145 (9) | 0.0120 (9) | 0.0280 (12) | 0.000 | 0.0057 (9) | 0.000 |
O3 | 0.0205 (8) | 0.0279 (8) | 0.0237 (9) | 0.0037 (6) | 0.0117 (7) | −0.0002 (7) |
O4 | 0.0189 (7) | 0.0188 (7) | 0.0234 (8) | −0.0027 (5) | 0.0092 (6) | −0.0008 (6) |
O5 | 0.0201 (7) | 0.0249 (8) | 0.0165 (7) | 0.0010 (6) | 0.0058 (6) | 0.0004 (6) |
Ba1—O2i | 2.665 (2) | Al1—O3viii | 1.6653 (17) |
Ba1—O1ii | 2.8689 (14) | Al1—O4 | 1.6692 (16) |
Ba1—O1 | 2.8689 (14) | Al1—O5 | 1.6784 (16) |
Ba1—O5 | 2.9307 (17) | Al1—O1 | 1.6830 (9) |
Ba1—O5iii | 2.9307 (17) | Al1—Ba1ii | 3.6201 (6) |
Ba1—O3iv | 2.9599 (17) | Al2—O3 | 1.6530 (17) |
Ba1—O3v | 2.9599 (17) | Al2—O5ix | 1.6615 (16) |
Ba1—O4vi | 3.1212 (16) | Al2—O4 | 1.6656 (16) |
Ba1—O4i | 3.1212 (16) | Al2—O2 | 1.6710 (10) |
Ba1—Si1ii | 3.6201 (6) | Al2—Ba1x | 3.6261 (6) |
Ba1—Al1ii | 3.6201 (6) | Al2—Ba1v | 3.8164 (7) |
Ba1—Al1vii | 3.6201 (6) | ||
O2i—Ba1—O1ii | 140.20 (3) | Si1ii—Ba1—Al1vii | 82.999 (19) |
O2i—Ba1—O1 | 140.20 (3) | Al1ii—Ba1—Al1vii | 82.999 (19) |
O1ii—Ba1—O1 | 79.60 (7) | O3viii—Al1—O4 | 112.34 (9) |
O2i—Ba1—O5 | 107.51 (5) | O3viii—Al1—O5 | 112.99 (9) |
O1ii—Ba1—O5 | 97.71 (4) | O4—Al1—O5 | 109.76 (9) |
O1—Ba1—O5 | 54.00 (3) | O3viii—Al1—O1 | 103.65 (7) |
O2i—Ba1—O5iii | 107.51 (5) | O4—Al1—O1 | 114.57 (9) |
O1ii—Ba1—O5iii | 54.00 (3) | O5—Al1—O1 | 103.15 (7) |
O1—Ba1—O5iii | 97.71 (4) | O3viii—Al1—Ba1ii | 53.82 (6) |
O5—Ba1—O5iii | 68.66 (6) | O4—Al1—Ba1ii | 138.40 (6) |
O2i—Ba1—O3iv | 104.57 (5) | O5—Al1—Ba1ii | 111.58 (6) |
O1ii—Ba1—O3iv | 53.66 (3) | O1—Al1—Ba1ii | 50.77 (4) |
O1—Ba1—O3iv | 101.40 (4) | O3viii—Al1—Ba1 | 117.42 (6) |
O5—Ba1—O3iv | 147.75 (4) | O4—Al1—Ba1 | 130.14 (6) |
O5iii—Ba1—O3iv | 98.60 (4) | O5—Al1—Ba1 | 52.68 (6) |
O2i—Ba1—O3v | 104.57 (5) | O1—Al1—Ba1 | 50.57 (4) |
O1ii—Ba1—O3v | 101.40 (4) | Ba1ii—Al1—Ba1 | 74.935 (13) |
O1—Ba1—O3v | 53.66 (3) | O3—Al2—O5ix | 112.15 (8) |
O5—Ba1—O3v | 98.60 (4) | O3—Al2—O4 | 112.17 (9) |
O5iii—Ba1—O3v | 147.75 (4) | O5ix—Al2—O4 | 113.39 (9) |
O3iv—Ba1—O3v | 76.22 (7) | O3—Al2—O2 | 107.93 (10) |
O2i—Ba1—O4vi | 52.58 (3) | O5ix—Al2—O2 | 108.40 (10) |
O1ii—Ba1—O4vi | 167.19 (4) | O4—Al2—O2 | 102.11 (9) |
O1—Ba1—O4vi | 87.64 (4) | O3—Al2—Ba1x | 126.50 (6) |
O5—Ba1—O4vi | 73.50 (4) | O5ix—Al2—Ba1x | 119.38 (6) |
O5iii—Ba1—O4vi | 127.68 (4) | O4—Al2—Ba1x | 59.22 (6) |
O3iv—Ba1—O4vi | 131.41 (4) | O2—Al2—Ba1x | 43.15 (7) |
O3v—Ba1—O4vi | 71.44 (4) | O3—Al2—Ba1v | 47.42 (6) |
O2i—Ba1—O4i | 52.58 (3) | O5ix—Al2—Ba1v | 142.61 (6) |
O1ii—Ba1—O4i | 87.64 (4) | O4—Al2—Ba1v | 103.92 (6) |
O1—Ba1—O4i | 167.19 (4) | O2—Al2—Ba1v | 64.10 (9) |
O5—Ba1—O4i | 127.68 (4) | Ba1x—Al2—Ba1v | 81.459 (12) |
O5iii—Ba1—O4i | 73.50 (4) | Si1vii—O1—Al1vii | 0.00 (6) |
O3iv—Ba1—O4i | 71.44 (4) | Si1vii—O1—Al1 | 140.97 (14) |
O3v—Ba1—O4i | 131.41 (4) | Al1vii—O1—Al1 | 140.97 (14) |
O4vi—Ba1—O4i | 105.08 (6) | Si1vii—O1—Ba1ii | 102.49 (4) |
O2i—Ba1—Si1ii | 127.17 (3) | Al1vii—O1—Ba1ii | 102.49 (4) |
O1ii—Ba1—Si1ii | 27.026 (13) | Al1—O1—Ba1ii | 102.21 (4) |
O1—Ba1—Si1ii | 87.57 (3) | Si1vii—O1—Ba1 | 102.21 (4) |
O5—Ba1—Si1ii | 122.16 (3) | Al1vii—O1—Ba1 | 102.21 (4) |
O5iii—Ba1—Si1ii | 77.58 (3) | Al1—O1—Ba1 | 102.49 (4) |
O3iv—Ba1—Si1ii | 27.01 (3) | Ba1ii—O1—Ba1 | 100.40 (7) |
O3v—Ba1—Si1ii | 85.81 (4) | Al2—O2—Si2xi | 135.57 (14) |
O4vi—Ba1—Si1ii | 154.72 (3) | Al2—O2—Al2xi | 135.57 (14) |
O4i—Ba1—Si1ii | 81.50 (3) | Si2xi—O2—Al2xi | 0.00 (7) |
O2i—Ba1—Al1ii | 127.17 (3) | Al2—O2—Ba1x | 111.45 (7) |
O1ii—Ba1—Al1ii | 27.026 (13) | Si2xi—O2—Ba1x | 111.45 (7) |
O1—Ba1—Al1ii | 87.57 (3) | Al2xi—O2—Ba1x | 111.45 (7) |
O5—Ba1—Al1ii | 122.16 (3) | Al2—O3—Si1vi | 150.59 (12) |
O5iii—Ba1—Al1ii | 77.58 (3) | Al2—O3—Al1vi | 150.59 (12) |
O3iv—Ba1—Al1ii | 27.01 (3) | Si1vi—O3—Al1vi | 0.00 (6) |
O3v—Ba1—Al1ii | 85.81 (4) | Al2—O3—Ba1v | 108.30 (7) |
O4vi—Ba1—Al1ii | 154.72 (3) | Si1vi—O3—Ba1v | 99.16 (7) |
O4i—Ba1—Al1ii | 81.50 (3) | Al1vi—O3—Ba1v | 99.16 (7) |
Si1ii—Ba1—Al1ii | 0.00 (3) | Al2—O4—Al1 | 128.89 (10) |
O2i—Ba1—Al1vii | 127.17 (3) | Al2—O4—Ba1x | 93.49 (7) |
O1ii—Ba1—Al1vii | 87.57 (3) | Al1—O4—Ba1x | 137.31 (8) |
O1—Ba1—Al1vii | 27.026 (13) | Si2ix—O5—Al2ix | 0.00 (6) |
O5—Ba1—Al1vii | 77.58 (3) | Si2ix—O5—Al1 | 139.61 (11) |
O5iii—Ba1—Al1vii | 122.16 (3) | Al2ix—O5—Al1 | 139.61 (11) |
O3iv—Ba1—Al1vii | 85.81 (4) | Si2ix—O5—Ba1 | 120.00 (8) |
O3v—Ba1—Al1vii | 27.01 (3) | Al2ix—O5—Ba1 | 120.00 (8) |
O4vi—Ba1—Al1vii | 81.50 (3) | Al1—O5—Ba1 | 100.22 (7) |
O4i—Ba1—Al1vii | 154.72 (3) |
Symmetry codes: (i) x+1/2, y−1/2, z; (ii) −x, −y, −z; (iii) x, −y, z; (iv) −x+1/2, y−1/2, −z; (v) −x+1/2, −y+1/2, −z; (vi) x+1/2, −y+1/2, z; (vii) −x, y, −z; (viii) x−1/2, −y+1/2, z; (ix) −x+1/2, −y+1/2, −z+1; (x) x−1/2, y+1/2, z; (xi) x, −y+1, z. |
Al1.88Ba0.94O8Si2.12 | F(000) = 682 |
Mr = 367.03 | Dx = 3.311 Mg m−3 |
Monoclinic, C2/m | Mo Kα radiation, λ = 0.71073 Å |
a = 8.633 (6) Å | Cell parameters from 14 reflections |
b = 13.063 (8) Å | θ = 12.3–14.2° |
c = 7.214 (5) Å | µ = 5.65 mm−1 |
β = 115.17 (5)° | T = 298 K |
V = 736.3 (9) Å3 | Block, colourless |
Z = 4 | 0.6 × 0.6 × 0.3 mm |
Nicolet P3 diffractometer | 1111 reflections with I > 2σ(I) |
Radiation source: normal-focus sealed tube | Rint = 0.049 |
Graphite monochromator | θmax = 30.0°, θmin = 3.0° |
ω scans | h = 0→12 |
Absorption correction: ψ scan (North et al., 1968) | k = 0→18 |
Tmin = 0.127, Tmax = 0.551 | l = −10→9 |
1169 measured reflections | 2 standard reflections every 50 reflections |
1112 independent reflections | intensity decay: none |
Refinement on F2 | Primary atom site location: heavy-atom method |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.032 | w = 1/[σ2(Fo2) + (0.0373P)2 + 6.7094P] where P = (Fo2 + 2Fc2)/3 |
wR(F2) = 0.095 | (Δ/σ)max < 0.001 |
S = 1.36 | Δρmax = 1.31 e Å−3 |
1112 reflections | Δρmin = −1.03 e Å−3 |
65 parameters | Extinction correction: SHELXL97 (Sheldrick, 1997), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
0 restraints | Extinction coefficient: 0.0261 (16) |
Al1.88Ba0.94O8Si2.12 | V = 736.3 (9) Å3 |
Mr = 367.03 | Z = 4 |
Monoclinic, C2/m | Mo Kα radiation |
a = 8.633 (6) Å | µ = 5.65 mm−1 |
b = 13.063 (8) Å | T = 298 K |
c = 7.214 (5) Å | 0.6 × 0.6 × 0.3 mm |
β = 115.17 (5)° |
Nicolet P3 diffractometer | 1111 reflections with I > 2σ(I) |
Absorption correction: ψ scan (North et al., 1968) | Rint = 0.049 |
Tmin = 0.127, Tmax = 0.551 | 2 standard reflections every 50 reflections |
1169 measured reflections | intensity decay: none |
1112 independent reflections |
R[F2 > 2σ(F2)] = 0.032 | 65 parameters |
wR(F2) = 0.095 | 0 restraints |
S = 1.36 | Δρmax = 1.31 e Å−3 |
1112 reflections | Δρmin = −1.03 e Å−3 |
Experimental. Scan rates, dependent on pre-scan intensity Ip, were variable in the range 1.0 (Ip<150) to 29.3 (Ip>2500)° ω min−1. The scan width was fixed at 0.6° ω. Stationary crystal background counts were made at 1° in ω on either side of the Bragg angle each for 25% of the total (peak plus background) count time. Intensity data, in terms of the reflections allowed by C-centring, are in fact 99.4% complete. |
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. |
Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger. |
x | y | z | Uiso*/Ueq | Occ. (<1) | |
Ba1 | 0.28270 (5) | 0.0000 | 0.13057 (6) | 0.0203 (2) | 0.938 (5) |
Al1 | 0.00832 (15) | 0.18272 (9) | 0.22450 (18) | 0.0167 (4) | 0.469 (2) |
Si1 | 0.00832 (15) | 0.18272 (9) | 0.22450 (18) | 0.0167 (4) | 0.531 (2) |
Al2 | 0.20313 (15) | 0.38148 (10) | 0.34697 (18) | 0.0165 (3) | 0.469 (2) |
Si2 | 0.20313 (15) | 0.38148 (10) | 0.34697 (18) | 0.0165 (3) | 0.531 (2) |
O1 | 0.0000 | 0.1381 (3) | 0.0000 | 0.0192 (8) | |
O2 | 0.1209 (6) | 0.5000 | 0.2878 (8) | 0.0220 (9) | |
O3 | 0.3266 (5) | 0.3626 (3) | 0.2241 (5) | 0.0259 (7) | |
O4 | 0.0251 (4) | 0.3101 (3) | 0.2520 (6) | 0.0250 (7) | |
O5 | 0.1865 (4) | 0.1264 (3) | 0.3970 (5) | 0.0245 (7) |
U11 | U22 | U33 | U12 | U13 | U23 | |
Ba1 | 0.0171 (3) | 0.0182 (3) | 0.0232 (3) | 0.000 | 0.00635 (16) | 0.000 |
Al1 | 0.0166 (6) | 0.0131 (6) | 0.0185 (6) | −0.0017 (4) | 0.0056 (4) | −0.0002 (4) |
Si1 | 0.0166 (6) | 0.0131 (6) | 0.0185 (6) | −0.0017 (4) | 0.0056 (4) | −0.0002 (4) |
Al2 | 0.0170 (6) | 0.0140 (6) | 0.0166 (6) | −0.0013 (4) | 0.0054 (4) | 0.0003 (4) |
Si2 | 0.0170 (6) | 0.0140 (6) | 0.0166 (6) | −0.0013 (4) | 0.0054 (4) | 0.0003 (4) |
O1 | 0.023 (2) | 0.0156 (19) | 0.0177 (18) | 0.000 | 0.0076 (16) | 0.000 |
O2 | 0.020 (2) | 0.0100 (18) | 0.032 (2) | 0.000 | 0.0071 (18) | 0.000 |
O3 | 0.0267 (16) | 0.0248 (17) | 0.0249 (16) | 0.0031 (13) | 0.0096 (13) | 0.0016 (13) |
O4 | 0.0231 (15) | 0.0182 (15) | 0.0337 (17) | −0.0008 (12) | 0.0120 (13) | 0.0031 (13) |
O5 | 0.0232 (15) | 0.0255 (16) | 0.0221 (15) | 0.0004 (13) | 0.0072 (12) | −0.0030 (13) |
Ba1—O2i | 2.645 (5) | Al2—O4 | 1.675 (4) |
Ba1—O1 | 2.853 (3) | Al2—O2 | 1.681 (2) |
Ba1—O1ii | 2.853 (3) | Al2—O5ix | 1.683 (4) |
Ba1—O5iii | 2.910 (4) | Al2—Ba1x | 3.632 (3) |
Ba1—O5 | 2.910 (4) | Al2—Ba1v | 3.826 (3) |
Ba1—O3iv | 2.933 (4) | O1—Si1vii | 1.694 (2) |
Ba1—O3v | 2.933 (4) | O1—Al1vii | 1.694 (2) |
Ba1—O4vi | 3.120 (4) | O1—Ba1ii | 2.853 (3) |
Ba1—O4i | 3.120 (4) | O2—Si2xi | 1.681 (2) |
Ba1—Si1ii | 3.619 (2) | O2—Al2xi | 1.681 (2) |
Ba1—Al1ii | 3.619 (2) | O2—Ba1x | 2.645 (5) |
Ba1—Al1vii | 3.619 (2) | O3—Si1vi | 1.676 (4) |
Al1—O4 | 1.675 (4) | O3—Al1vi | 1.676 (4) |
Al1—O3viii | 1.676 (4) | O3—Ba1v | 2.933 (4) |
Al1—O5 | 1.682 (4) | O4—Ba1x | 3.120 (4) |
Al1—O1 | 1.694 (2) | O5—Si2ix | 1.683 (4) |
Al1—Ba1ii | 3.619 (2) | O5—Al2ix | 1.683 (4) |
Al2—O3 | 1.669 (4) | ||
O2i—Ba1—O1 | 140.79 (8) | Si1ii—Ba1—Al1vii | 82.53 (7) |
O2i—Ba1—O1ii | 140.79 (8) | Al1ii—Ba1—Al1vii | 82.53 (7) |
O1—Ba1—O1ii | 78.42 (15) | O4—Al1—O3viii | 112.64 (19) |
O2i—Ba1—O5iii | 106.85 (12) | O4—Al1—O5 | 109.97 (19) |
O1—Ba1—O5iii | 97.61 (9) | O3viii—Al1—O5 | 114.1 (2) |
O1ii—Ba1—O5iii | 54.21 (8) | O4—Al1—O1 | 114.9 (2) |
O2i—Ba1—O5 | 106.85 (12) | O3viii—Al1—O1 | 102.58 (16) |
O1—Ba1—O5 | 54.21 (8) | O5—Al1—O1 | 102.13 (17) |
O1ii—Ba1—O5 | 97.61 (9) | O4—Al1—Ba1ii | 137.57 (14) |
O5iii—Ba1—O5 | 69.13 (16) | O3viii—Al1—Ba1ii | 53.00 (13) |
O2i—Ba1—O3iv | 105.13 (12) | O5—Al1—Ba1ii | 112.10 (15) |
O1—Ba1—O3iv | 100.73 (10) | O1—Al1—Ba1ii | 50.34 (10) |
O1ii—Ba1—O3iv | 54.03 (8) | O4—Al1—Ba1 | 130.25 (14) |
O5iii—Ba1—O3iv | 98.79 (11) | O3viii—Al1—Ba1 | 116.93 (14) |
O5—Ba1—O3iv | 147.89 (10) | O5—Al1—Ba1 | 52.06 (13) |
O2i—Ba1—O3v | 105.13 (12) | O1—Al1—Ba1 | 50.19 (10) |
O1—Ba1—O3v | 54.03 (8) | Ba1ii—Al1—Ba1 | 75.25 (6) |
O1ii—Ba1—O3v | 100.73 (10) | O3—Al2—O4 | 112.5 (2) |
O5iii—Ba1—O3v | 147.89 (10) | O3—Al2—O2 | 107.3 (2) |
O5—Ba1—O3v | 98.79 (11) | O4—Al2—O2 | 101.2 (2) |
O3iv—Ba1—O3v | 75.44 (15) | O3—Al2—O5ix | 112.49 (19) |
O2i—Ba1—O4vi | 52.66 (7) | O4—Al2—O5ix | 114.1 (2) |
O1—Ba1—O4vi | 88.14 (11) | O2—Al2—O5ix | 108.4 (2) |
O1ii—Ba1—O4vi | 166.50 (10) | O3—Al2—Ba1x | 125.59 (14) |
O5iii—Ba1—O4vi | 127.67 (11) | O4—Al2—Ba1x | 59.05 (13) |
O5—Ba1—O4vi | 73.10 (11) | O2—Al2—Ba1x | 42.37 (15) |
O3iv—Ba1—O4vi | 131.27 (10) | O5ix—Al2—Ba1x | 119.56 (14) |
O3v—Ba1—O4vi | 71.77 (11) | O3—Al2—Ba1v | 46.33 (13) |
O2i—Ba1—O4i | 52.66 (7) | O4—Al2—Ba1v | 103.42 (14) |
O1—Ba1—O4i | 166.50 (10) | O2—Al2—Ba1v | 64.55 (18) |
O1ii—Ba1—O4i | 88.14 (11) | O5ix—Al2—Ba1v | 142.45 (14) |
O5iii—Ba1—O4i | 73.10 (11) | Ba1x—Al2—Ba1v | 81.33 (5) |
O5—Ba1—O4i | 127.67 (11) | Al1—O1—Si1vii | 139.7 (3) |
O3iv—Ba1—O4i | 71.77 (11) | Al1—O1—Al1vii | 139.7 (3) |
O3v—Ba1—O4i | 131.27 (10) | Si1vii—O1—Al1vii | 0.00 (13) |
O4vi—Ba1—O4i | 105.28 (14) | Al1—O1—Ba1ii | 102.46 (9) |
O2i—Ba1—Si1ii | 127.66 (7) | Si1vii—O1—Ba1ii | 102.68 (9) |
O1—Ba1—Si1ii | 86.81 (9) | Al1vii—O1—Ba1ii | 102.68 (9) |
O1ii—Ba1—Si1ii | 27.20 (3) | Al1—O1—Ba1 | 102.68 (9) |
O5iii—Ba1—Si1ii | 77.65 (9) | Si1vii—O1—Ba1 | 102.46 (9) |
O5—Ba1—Si1ii | 122.31 (8) | Al1vii—O1—Ba1 | 102.46 (9) |
O3iv—Ba1—Si1ii | 27.14 (8) | Ba1ii—O1—Ba1 | 101.58 (15) |
O3v—Ba1—Si1ii | 85.25 (9) | Al2—O2—Si2xi | 134.2 (3) |
O4vi—Ba1—Si1ii | 154.64 (8) | Al2—O2—Al2xi | 134.2 (3) |
O4i—Ba1—Si1ii | 81.68 (9) | Si2xi—O2—Al2xi | 0.00 (15) |
O2i—Ba1—Al1ii | 127.66 (7) | Al2—O2—Ba1x | 112.27 (15) |
O1—Ba1—Al1ii | 86.81 (9) | Si2xi—O2—Ba1x | 112.27 (15) |
O1ii—Ba1—Al1ii | 27.20 (3) | Al2xi—O2—Ba1x | 112.27 (15) |
O5iii—Ba1—Al1ii | 77.65 (9) | Al2—O3—Si1vi | 149.3 (2) |
O5—Ba1—Al1ii | 122.31 (8) | Al2—O3—Al1vi | 149.3 (2) |
O3iv—Ba1—Al1ii | 27.14 (8) | Si1vi—O3—Al1vi | 0.00 (13) |
O3v—Ba1—Al1ii | 85.25 (9) | Al2—O3—Ba1v | 109.37 (17) |
O4vi—Ba1—Al1ii | 154.64 (8) | Si1vi—O3—Ba1v | 99.85 (16) |
O4i—Ba1—Al1ii | 81.68 (9) | Al1vi—O3—Ba1v | 99.85 (16) |
Si1ii—Ba1—Al1ii | 0.00 (7) | Al2—O4—Al1 | 128.3 (2) |
O2i—Ba1—Al1vii | 127.66 (7) | Al2—O4—Ba1x | 93.54 (16) |
O1—Ba1—Al1vii | 27.20 (3) | Al1—O4—Ba1x | 137.96 (18) |
O1ii—Ba1—Al1vii | 86.82 (9) | Al1—O5—Si2ix | 138.7 (2) |
O5iii—Ba1—Al1vii | 122.31 (8) | Al1—O5—Al2ix | 138.7 (2) |
O5—Ba1—Al1vii | 77.65 (9) | Si2ix—O5—Al2ix | 0.00 (14) |
O3iv—Ba1—Al1vii | 85.25 (9) | Al1—O5—Ba1 | 100.82 (16) |
O3v—Ba1—Al1vii | 27.14 (8) | Si2ix—O5—Ba1 | 120.20 (18) |
O4vi—Ba1—Al1vii | 81.68 (9) | Al2ix—O5—Ba1 | 120.20 (18) |
O4i—Ba1—Al1vii | 154.64 (8) |
Symmetry codes: (i) x+1/2, y−1/2, z; (ii) −x, −y, −z; (iii) x, −y, z; (iv) −x+1/2, y−1/2, −z; (v) −x+1/2, −y+1/2, −z; (vi) x+1/2, −y+1/2, z; (vii) −x, y, −z; (viii) x−1/2, −y+1/2, z; (ix) −x+1/2, −y+1/2, −z+1; (x) x−1/2, y+1/2, z; (xi) x, −y+1, z. |
Experimental details
(I) | (II) | |
Crystal data | ||
Chemical formula | Al1.60Ba0.80O8Si2.40 | Al1.88Ba0.94O8Si2.12 |
Mr | 348.12 | 367.03 |
Crystal system, space group | Monoclinic, C2/m | Monoclinic, C2/m |
Temperature (K) | 292 | 298 |
a, b, c (Å) | 8.6090 (8), 13.0658 (12), 7.2047 (7) | 8.633 (6), 13.063 (8), 7.214 (5) |
β (°) | 115.418 (2) | 115.17 (5) |
V (Å3) | 731.96 (12) | 736.3 (9) |
Z | 4 | 4 |
Radiation type | Mo Kα | Mo Kα |
µ (mm−1) | 4.96 | 5.65 |
Crystal size (mm) | 0.20 × 0.18 × 0.14 | 0.6 × 0.6 × 0.3 |
Data collection | ||
Diffractometer | Bruker SMART 1000 CCD area-detector diffractometer | Nicolet P3 diffractometer |
Absorption correction | Multi-scan (SADABS; Bruker, 2000) | ψ scan (North et al., 1968) |
Tmin, Tmax | 0.349, 0.500 | 0.127, 0.551 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 3542, 1366, 1223 | 1169, 1112, 1111 |
Rint | 0.022 | 0.049 |
(sin θ/λ)max (Å−1) | 0.756 | 0.703 |
Refinement | ||
R[F2 > 2σ(F2)], wR(F2), S | 0.022, 0.056, 1.07 | 0.032, 0.095, 1.36 |
No. of reflections | 1366 | 1112 |
No. of parameters | 64 | 65 |
Δρmax, Δρmin (e Å−3) | 0.73, −0.82 | 1.31, −1.03 |
Computer programs: SMART (Bruker, 1998), P3 software (Nicolet, 1980), SAINT (Bruker, 2000), P3 software, SAINT, RDNIC (Howie, 1980), SHELXS86 (Sheldrick, 1990), SHELXL97 (Sheldrick, 1997), ORTEX in OSCAIL (McArdle, 1994, 2000) and ATOMS (Dowty, 1999), SHELXL97.
Al | Si | Ba | |
1 | 35.6 (5) | 48.5 (6) | 15.9 (2) |
2 | 34.9 (6) | 49.5 (7) | 15.6 (2) |
3 | 33.5 (6) | 51.8 (7) | 14.7 (2) |
4 | 34.4 (4) | 49.6 (5) | 16.09 (13) |
5 | 35.6 (5) | 48.4 (6) | 16.01 (16) |
6 | 35.9 (6) | 47.6 (7) | 16.57 (20) |
7 | 34.3 (9) | 49.3 (10) | 16.3 (3) |
Mean | 34.9 | 49.2 | 15.9 |
σn-1 | 0.9 | 1.3 | 0.6 |
(I) (x = 1/5) | (II) (x = 0.06) | |
Ba1-O2i | 2.665 (2) | 2.645 (2) |
Ba1-O1 | 2.8689 (14) | 2.853 (3) |
Ba1-O5 | 2.9307 (17) | 2.910 (4) |
Ba1-O3ii | 2.9599 (17) | 2.933 (4) |
Ba1-O4i | 3.1212 (16) | 3.120 (4) |
M1-O3iii | 1.6653 (17) | 1.676 (4) |
M1-O4 | 1.6692 (16) | 1.675 (4) |
M1-O5 | 1.6784 (16) | 1.682 (4) |
M1-O1 | 1.6830 (9) | 1.694 (2) |
M2-O3 | 1.6530 (17) | 1.669 (4) |
M2-O5iv | 1.6615 (16) | 1.683 (4) |
M2-O4 | 1.6656 (16) | 1.675 (4) |
M2-O2 | 1.6710 (10) | 1.681 (2) |
O4-M1-O3iii | 112.34 (9) | 112.64 (19) |
O5-M1-O3iii | 112.99 (9) | 114.1 (2) |
O1-M1-O3iii | 103.65 (7) | 102.58 (16) |
O5-M1-O4 | 109.76 (9) | 109.97 (19) |
O1-M1-O4 | 114.57 (9) | 114.9 (2) |
O1-M1-O5 | 103.15 (7) | 102.13 (17) |
O3-M2-O5iv | 112.15 (8) | 112.49 (19) |
O4-M2-O5iv | 113.39 (9) | 114.1 (2) |
O2-M2-O5iv | 108.40 (10) | 108.4 (2) |
O4-M2-O3 | 112.17 (9) | 112.5 (2) |
O2-M2-O3 | 107.93 (10) | 107.3 (2) |
O2-M2-O4 | 102.11 (9) | 101.2 (2) |
M1-O1-M1v | 140.97 (14) | 139.7 (3) |
M2-O2-M2vi | 135.57 (14) | 134.2 (3) |
M2-O3-M1vii | 150.59 (12) | 149.3 (2) |
M1-O4-M2 | 128.89 (10) | 128.3 (2) |
M1-O5-M2iv | 139.61 (11) | 138.7 (2) |
M1 and M2 represent the Al1/Si1 and Al2/Si2 sites, respectively. Symmetry codes: (i) 1/2 + x, y − 1/2, z; (ii) 1/2 − x, y − 1/2, −z; (iii) x − 1/2, 1/2 − y, z; (iv) 1/2 − x, 1/2 − y, 1 − z; (v) −x, y, −z; (vi) x, 1 − y, z; (vii) 1/2 + x, 1/2 − y, z. |
Composition (I) (x = 1/5) | Composition (II) (x = 0.06) | |||
Expected | Calculated | Expected | Calculated | |
Ba1 | 1.60 | 1.65 | 1.88 | 1.74 |
Al1/Si1 | 3.60 | 3.60 | 3.53 | 3.55 |
Al2/Si2 | 3.60 | 3.71 | 3.53 | 3.59 |
The mineral celsian, with the ideal formula BaAl2Si2O8, is a barium feldspar. It is the only ternary phase within the BaO-Al2O3—SiO2 phase diagram (Drummond, 1990), and is of interest due to its resistance to oxidation and reduction and its low coefficient of thermal expansion, amongst other properties (Bošković et al., 1999). Originally, celsian was believed to have space group C2/m, with disorder of Al and Si over two sets of 8j sites (Taylor et al., 1934), and indeed this provides an adequate description of the structure (Newnham & Megaw, 1960). It was shown, however, that the structure is better described by an I2/c supercell with a doubled c axis, although the differences are very subtle (Newnham & Megaw, 1960; Ribbe & Griffen, 1976). Similarly, in the polymorph paracelsian, small differences in the Si/Al ordering lead to a slight monoclinic distortion, space group P21/a, with a strong orthorhombic (Pnam) subcell (Smith, 1953; Chiari et al., 1985). Finally, a hexagonal form, hexacelsian, is stable only at temperatures above 1863 K (Yoshiki & Matsumoto, 1951; Kakeuchi, 1958).
Celsian forms a continous solid solution of formula [K1 − xBax][Al1 + xSi3 − x]O8 with orthoclase, the ideal formula of which is KAlSi3O8 (Thomas, 1950). Thus in fact, previous reports on celsian are on the x = 0.84 and x = 0.95 members of this solid solution series (Newnham & Megaw, 1960; Ribbe & Griffen, 1976), whereas paracelsian has been consistently reported as the stoichiometric end-member (x = 1) (Smith, 1953; Balakin & Belov, 1960; Chiari et al., 1985).
The compounds studied here, (I) (with x = 0.06) and (II) (with x = 1/5), were by-products of melts of Ba-containing mixtures contained in platinum envelopes within aluminosilicate crucibles. The composition of (I) determined by EDXA Please define indicated that K was absent. However, the Ba:Al:Si ratio was non-stoichiometric and, apart from giving a range of overall compositions (Table 1), suggested either an excess of Si or a deficiency of Ba. The former is possible because of the open framework present in feldspars, and thus excess Si may be easily accommodated. Single-crystal X-ray diffraction was thus carried out, and the unit cell was determined to be comparable with the subcell of celsian (see Experimental). Further structure analysis was carried out in this subcell, as it adequately describes the structure and the emphasis here is primarily on the determination of the composition. \sch
The structure of (I) was solved without reference to the previously determined structure of (II) and was, along with (II), found to be consistent with that of orthoclase. No evidence was found for interstitial Si, but rather the overall scattering and refined displacement parameters tended to point to Ba deficiency. Indeed, refinement of the Ba and Al/Si site occupancies in the manner noted below gave improved refinement and a final composition of Ba0.80Al1.60Si2.40O8. A second crystal from a completely different synthesis, (II), was similarly refined to give the composition Ba0.94Al1.88Si2.12O8. Thus, rather than a solid solution with orthoclase, these indicate a slight solid solution with SiO2 and solid solution formula Ba1 − xAl2–2xSi2 + 2xO8, where the two refinements give x = 0.20 and x = 0.06, with respective refined values of 0.2024 (14) and 0.062 (5).
The atoms selected for inclusion in the asymmetric unit and the labelling scheme used in the refinement of (I) can be seen in Fig. 1, along with the M—O (M is Al or Si) connectivity. Figs. 2 and 3 display the connectivity of the aluminosilicate framework more extensively. Precisely the same selection of atoms and labelling scheme were used in the final refinement of (II). In (I) and (II), Ba—O (nine-coordinate Ba) and M—O (tetrahedral M) distances [those for (II) given in square brackets] are in the ranges 2.665 (2)–3.1212 (16) [2.645 (5)–3.120 (4)] and 1.6530 (17)–1.6830 (9) Å [1.675 (4)–1.694 (2) Å], respectively, and these are unexceptional (see also Table 2). The difference in each pair of ranges, although they overlap within the pair, is entirely consistent with the change in Ba and Al content between (I) and (II).
Previous reports have cited similar compositions. Ba0.75Al1.5Si2.5O8 was found, though, to have the hollandite structure (Zhang & Burnham, 1994). This is, perhaps, not surprising, as it has been shown that certain feldspar materials can be transformed to hollandite under high pressure (Ringwood et al., 1967). KAlSi3O8 (sanidine) transforms to hollandite under 120 kbar s of pressure (1 bar = 10 5 Pa) at 1173 K (Ringwood et al., 1967) and celsian itself partially transforms under similar conditions (Reid & Ringwood, 1969). This is also consistent with the observation that the formation of celsian is more difficult in compositions with high SiO2 content (Thomas, 1950).
Bond-valence sums (BVS; Brown & Altermatt, 1985) calculated for each composition (Table 3) provide a check on the structure solution and the assumptions made. The composition Ba0.80Al1.60Si2.40O8 gives values of 3.60 for Al1/Si1 and 3.71 for Al2/Si2, which compare well with the expected value of 3.60 for Al:Si 0.40:0.60. The BVS for Ba is 1.65, compared with the expected value of 1.60. This is in reasonable agreement and provides further evidence for Ba deficiency. Similar results are obtained for the other composition. In both cases, slightly higher values are obtained for Al2/Si2, which might indicate more Si on this site. This, however, would have the effect of reducing the BVS on the Al1/Si1 site which, in both cases, is in very good agreement with the expected values. Therefore, the model used is perceived as giving an adequate representation of the structures.