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Dibarium dititanium difluoride dioxide hepta­oxidodisilicate, Ba2Ti2Si2O9F2, is a new edge-sharing titanate with a unique titanium silicate framework. All atoms in the structure are in general positions. Titanium oxyfluoride octa­hedra combine with silicon tetra­hedra to form a double stacked chain, which is the base unit of the layered framework. The Ba atoms lie in channels that extend along the a axis.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270109007677/fn3013sup1.cif
Contains datablocks I, global

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270109007677/fn3013Isup2.hkl
Contains datablock I

Comment top

The number of known titanium silicate structures extends into the hundreds (Roberts et al., 1996), with more naturally occuring and synthetic examples being discovered each year. Of the naturally occurring silicates, many have found a variety of technological applications and thus create a need for a synthetic growth pathway. One such material, fresnoite, was discovered in sanbornite deposits in 1965 (Alfors et al., 1965). Ba2TiOSi2O7 [Is this fresnoite?] was refined in the P4bm space group (Moore, 1967). The unique titanium silicate network exhibits many desirable properties such as piezoelectric, electrooptic, pryoelectric and nonlinear optical (Haussühl et al., 1977). Due to these interesting properties and the fact that the material is otherwise difficult to grow, an exploration into the hydrothermal growth of fresnoite was undertaken. During the study, the title compound was synthesized as a minor product which crystallized in the Pbca space group.

The structure contains edge-sharing TiO5F octahedra and SiO4 tetrahedra (Fig. 1) which combine to form a novel titanium silicate framework. Both Ti atoms have five bonds to O, with average bond lengths of 1.93[7] and 1.94[8] Å for atoms Ti1 and Ti2, respectively. An F atom completes the octahedral environment for each Ti atom. The possibility of hydroxide rather than fluoride was eliminated by IR spectroscopy and differential scanning calorimetry/thermogravimetric analysis. None of the characteristic hydroxyl stretches was observed in the IR spectrum. The sample also displayed thermal and gravimetric stability beyond 1073 K. Energy-dispersive X-ray analysis confirmed substantial amounts of fluorine.

The F-site designation could not be unequivocally fixed by observing bond lengths. Metal–metal repulsion, similar to that observed in other edge-sharing titanium structures, causes a bond distortion (Dadachov et al. 1997). Therefore, bond-valence sums (Reference?) were used for a preliminary assignment of the F sites. Both F1 and F2 are significantly undersaturated when refined as O, with bond-valence sums of 1.237 and 1.351 v.u., respectively. Refinements as F provide much more reasonable valence sums of 0.951 and 1.038 v.u. To confirm the fluoride designation, IR stretches for Ti—F bonds were examined. However, these are difficult to assign because of overlap with many silicate bending vibrations. Confirmation was achieved by observation of a 722 cm-1 band, which is characteristic of titanium and other metal oxyfluoride complexes (Laptash et al. 1999). The absence of bands in the range 759–813 cm-1 (Clark & Errington, 1967) eliminates the possibility of any Si—F bonds. The SiO4 tetrahedra share one O atom, which forms an [Si2O7] pyrosilicate group that is confirmed by a 662 cm-1 band (Farmer, 1974). The other coordinating O atoms are involved in the overall framework.

The base unit of the framework (Fig. 2) is a double stacked chain which extends along the (200) plane. It consists of alternating edge-sharing titania and [Si2O7] groups. This chain has two levels, with the bottom layer also alternating between the aforementioned groups. However, the lower level is staggered so that the [Si2O7] group is directly beneath the edge-sharing Ti. In each octahedral or tetrahedral environment there is one O anion not participating in the propagating chain unit. This O atom serves to bridge one chain to the next to form the overall titanium silicate framework. The remaining F atoms do not participate in continuation of the framework; instead, they terminate with four bonds to both Ba1 and Ba2.

The titanium silicate network forms both channels (Fig. 3) and layers (Fig. 4) in which the Ba atoms reside. Atom Ba1 is located in a channel constructed of six-membered rings. These rings are composed of three titanium oxide and three silicon oxide environments. Each ring is bridged using three Ti—O—Si bonds. The rest of the channel is partially enclosed by Ti—F bonds. Like the Ba1 environment, the Ba2 channel also extends along the a axis. The ring structure, which forms the channel, is different in its composition. The first ring is a compilation of four Ti and two Si atoms bridged by O atoms. The second ring has the exact opposite ratio, with two Ti octahedra and four Si tetrahedra. These two rings alternate as the channel descends. Similar to the Ba1 channel, the rings also connect via three Ti—O—Si bridges. Three Ti—F bonds complete the sheath, just as in the previous channel. Since the titanium silicate chains are constrained to the (200) plane, the fluoride bonds and Ti—O—Si bridges are oriented in between this plane. This gives the illusion of a layered structure (Fig. 4). Both Ba1 and Ba2 are located in this plane.

Experimental top

Ba2Ti2Si2O9F2 was created by hydrothermal synthesis. A fresnoite powder, prepared by solid-state synthesis, was sealed in a silver ampoule with a solution of 6M KF. A 27 ml Inconel autoclave was used to heat the ampoule to 848 K to generate 20 000 psi (1 psi ~ 6893 Pa) of counter-pressure. After 7 d the ampoule was opened and the contents flushed with deionized water. Single crystals of fresnoite were the major product and polyhedral shaped crystals of the title compound were the minor product. Spectroscopic analysis: FT–IR (Medium?, ν, cm-1): 722 (m, ν TiOxFy) and 662 (s, νs Si—O—Si). Differential scanning calorimetry/thermogravimetric analysis: no thermal events before endotherm at 1096 K, weight loss 2.9%.

Computing details top

Data collection: CrystalClear (Molecular Structure Corporation & Rigaku, 2001); cell refinement: CrystalClear (Molecular Structure Corporation & Rigaku, 2001); data reduction: CrystalClear (Molecular Structure Corporation & Rigaku, 2001); program(s) used to solve structure: SHELXTL (Version 6.10; Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Version 6.10; Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 1999); software used to prepare material for publication: SHELXTL (Version 6.10; Sheldrick, 2008).

Figures top
[Figure 1] Fig. 1. A view of the asymmetric unit of Ba2Ti2Si2O9F2, with the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level. Symmetry-related atoms have been added to show the octahedral environments of atoms Ti1 and Ti2. [Symmetry codes: (ii) -x + 1/2, y - 1/2, z; (iv) x + 1/2, y, -z + 1/2; (vii) -x + 1/2, y + 1/2, z; (viii) x + 1/2, -y + 3/2, -z + 1.]
[Figure 2] Fig. 2. The base chain unit of the overall framework, projected slightly off the ab plane.
[Figure 3] Fig. 3. A view of the barium channels, which extend down the a axis.
[Figure 4] Fig. 4. The layered structure projected onto the ac plane. The titanium silicate layers occupy the (200) plane.
Dibarium dititanium difluoride dioxide heptaoxidodisilicate top
Crystal data top
Ba2Ti2Si2O9F2F(000) = 2192
Mr = 608.66Dx = 4.553 Mg m3
Orthorhombic, PbcaMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P2ac2abCell parameters from 11712 reflections
a = 8.7350 (17) Åθ = 1.9–29.1°
b = 10.832 (2) ŵ = 10.83 mm1
c = 18.769 (4) ÅT = 298 K
V = 1775.9 (6) Å3Dipyramid, colourless
Z = 80.12 × 0.11 × 0.09 mm
Data collection top
Rigaku AFC-8S Mercury CCD
diffractometer
1573 independent reflections
Radiation source: sealed tube1539 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.034
Detector resolution: 14.6306 pixels mm-1θmax = 25.0°, θmin = 2.2°
ω scansh = 1010
Absorption correction: multi-scan
(Jacobson, 1998)
k = 1212
Tmin = 0.303, Tmax = 0.376l = 2221
13481 measured reflections
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.026 w = 1/[σ2(Fo2) + (0.0196P)2 + 7.030P]
where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.058(Δ/σ)max = 0.001
S = 1.41Δρmax = 1.05 e Å3
1573 reflectionsΔρmin = 1.18 e Å3
155 parametersExtinction correction: SHELXL97 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
0 restraintsExtinction coefficient: 0.00357 (11)
Crystal data top
Ba2Ti2Si2O9F2V = 1775.9 (6) Å3
Mr = 608.66Z = 8
Orthorhombic, PbcaMo Kα radiation
a = 8.7350 (17) ŵ = 10.83 mm1
b = 10.832 (2) ÅT = 298 K
c = 18.769 (4) Å0.12 × 0.11 × 0.09 mm
Data collection top
Rigaku AFC-8S Mercury CCD
diffractometer
1573 independent reflections
Absorption correction: multi-scan
(Jacobson, 1998)
1539 reflections with I > 2σ(I)
Tmin = 0.303, Tmax = 0.376Rint = 0.034
13481 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.026155 parameters
wR(F2) = 0.0580 restraints
S = 1.41Δρmax = 1.05 e Å3
1573 reflectionsΔρmin = 1.18 e Å3
Special details top

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
Ba10.25284 (3)0.29962 (3)0.219371 (15)0.01152 (13)
Ba20.25779 (3)0.99744 (3)0.525840 (15)0.01157 (13)
Ti10.47045 (9)0.54018 (8)0.33768 (4)0.00601 (19)
Ti20.45107 (9)0.76231 (8)0.42248 (4)0.0064 (2)
Si10.08324 (14)0.51765 (12)0.33131 (6)0.0055 (3)
Si20.05925 (14)0.75851 (11)0.40983 (6)0.0050 (3)
O10.0225 (4)0.4444 (3)0.39980 (16)0.0100 (7)
O20.0063 (3)0.4701 (3)0.25822 (16)0.0086 (7)
O30.2667 (4)0.4971 (3)0.32545 (19)0.0116 (8)
O40.0532 (4)0.6666 (3)0.33927 (16)0.0097 (7)
O50.0208 (4)0.6907 (3)0.47678 (16)0.0097 (7)
O60.0303 (4)0.8794 (3)0.38276 (16)0.0085 (6)
O70.2372 (3)0.7845 (3)0.42972 (18)0.0095 (7)
O80.4538 (4)0.7095 (3)0.32213 (16)0.0085 (6)
O90.4623 (4)0.5954 (3)0.43748 (16)0.0088 (6)
F10.7016 (3)0.5582 (3)0.33567 (14)0.0124 (6)
F20.6782 (3)0.7712 (3)0.41695 (15)0.0157 (6)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Ba10.00979 (19)0.0151 (2)0.00970 (19)0.00282 (10)0.00078 (10)0.00137 (11)
Ba20.00751 (18)0.0175 (2)0.00970 (19)0.00075 (10)0.00063 (10)0.00331 (12)
Ti10.0054 (4)0.0060 (4)0.0067 (4)0.0002 (3)0.0008 (3)0.0003 (3)
Ti20.0063 (4)0.0060 (4)0.0070 (4)0.0000 (3)0.0002 (3)0.0001 (3)
Si10.0058 (6)0.0054 (6)0.0055 (6)0.0010 (5)0.0003 (5)0.0005 (4)
Si20.0048 (6)0.0052 (6)0.0050 (6)0.0002 (5)0.0002 (4)0.0001 (4)
O10.0110 (16)0.0102 (17)0.0088 (16)0.0022 (13)0.0022 (13)0.0028 (13)
O20.0094 (16)0.0076 (16)0.0089 (16)0.0005 (12)0.0004 (13)0.0012 (12)
O30.0052 (16)0.0158 (19)0.0137 (18)0.0003 (13)0.0016 (13)0.0011 (14)
O40.0137 (16)0.0073 (16)0.0081 (15)0.0007 (13)0.0004 (12)0.0009 (13)
O50.0115 (16)0.0106 (18)0.0070 (16)0.0024 (13)0.0026 (12)0.0015 (12)
O60.0086 (15)0.0064 (16)0.0104 (15)0.0014 (13)0.0007 (12)0.0002 (12)
O70.0050 (16)0.0134 (17)0.0102 (17)0.0016 (12)0.0006 (12)0.0004 (14)
O80.0102 (15)0.0076 (16)0.0079 (15)0.0005 (13)0.0003 (12)0.0004 (12)
O90.0125 (16)0.0079 (16)0.0060 (15)0.0004 (13)0.0003 (12)0.0006 (13)
F10.0082 (13)0.0140 (14)0.0150 (14)0.0018 (11)0.0005 (11)0.0002 (11)
F20.0103 (14)0.0217 (16)0.0151 (15)0.0004 (12)0.0001 (11)0.0018 (12)
Geometric parameters (Å, º) top
Ba1—F2i2.647 (3)Ti2—F21.989 (3)
Ba1—O8ii2.816 (3)Ti2—O1vii2.031 (3)
Ba1—F1i2.840 (3)Ti2—Ba1xi3.7338 (10)
Ba1—O8i2.851 (3)Ti2—Ba2ix3.7657 (10)
Ba1—O6iii2.863 (3)Ti2—Ba2ii3.9145 (10)
Ba1—O2iv2.914 (3)Ti2—Ba2viii4.0045 (10)
Ba1—O32.925 (4)Si1—O11.601 (3)
Ba1—O22.929 (3)Si1—O21.612 (3)
Ba1—F1v3.019 (3)Si1—O31.621 (3)
Ba1—O4ii3.164 (3)Si1—O41.641 (3)
Ba1—O4iii3.230 (3)Si2—O61.607 (3)
Ba1—Si13.4909 (13)Si2—O51.614 (3)
Ba2—F1vi2.713 (3)Si2—O71.623 (3)
Ba2—O9vii2.752 (3)Si2—O41.658 (3)
Ba2—O1viii2.773 (3)Si2—Ba1xii3.6757 (13)
Ba2—F2ix2.783 (3)O1—Ti2ii2.031 (3)
Ba2—O5viii2.810 (3)O1—Ba2vi2.773 (3)
Ba2—O9vi2.854 (3)O1—Ba2ii3.100 (3)
Ba2—O72.934 (4)O2—Ti1v1.979 (3)
Ba2—O6x2.945 (3)O2—Ba1v2.914 (3)
Ba2—O1vii3.100 (3)O4—Ba1vii3.164 (3)
Ba2—F2vi3.178 (3)O4—Ba1xii3.230 (3)
Ba2—O5vii3.242 (3)O5—Ti2vi1.973 (3)
Ba2—Ti1vi3.6093 (10)O5—Ba2vi2.810 (3)
Ti1—O31.855 (3)O5—Ba2ii3.242 (3)
Ti1—O81.863 (3)O6—Ti1vii2.006 (3)
Ti1—O91.968 (3)O6—Ba1xii2.863 (3)
Ti1—O2iv1.979 (3)O6—Ba2x2.945 (3)
Ti1—O6ii2.006 (3)O8—Ba1vii2.816 (3)
Ti1—F12.029 (3)O8—Ba1xi2.851 (3)
Ti1—Ti22.8899 (13)O9—Ba2ii2.752 (3)
Ti1—Ba2viii3.6093 (10)O9—Ba2viii2.854 (3)
Ti1—Ba1iv3.7445 (10)F1—Ba2viii2.713 (3)
Ti1—Ba1xi3.8582 (10)F1—Ba1xi2.840 (3)
Ti1—Ba1vii4.0783 (10)F1—Ba1iv3.019 (3)
Ti2—O91.832 (3)F2—Ba1xi2.647 (3)
Ti2—O71.888 (3)F2—Ba2ix2.783 (3)
Ti2—O81.969 (3)F2—Ba2viii3.178 (3)
Ti2—O5viii1.973 (3)
F2i—Ba1—O8ii140.14 (9)Ba2viii—Ti1—Ba1xi81.00 (2)
F2i—Ba1—F1i60.60 (9)Ba1iv—Ti1—Ba1xi90.85 (2)
O8ii—Ba1—F1i91.14 (9)O3—Ti1—Ba145.28 (11)
F2i—Ba1—O8i59.43 (8)O8—Ti1—Ba1121.90 (10)
O8ii—Ba1—O8i130.14 (11)O9—Ti1—Ba1136.44 (10)
F1i—Ba1—O8i57.27 (8)O2iv—Ti1—Ba146.02 (9)
F2i—Ba1—O6iii62.76 (9)O6ii—Ti1—Ba177.75 (9)
O8ii—Ba1—O6iii97.35 (9)F1—Ti1—Ba1122.44 (8)
F1i—Ba1—O6iii97.44 (8)Ti2—Ti1—Ba1146.92 (3)
O8i—Ba1—O6iii122.05 (9)Ba2viii—Ti1—Ba1131.67 (3)
F2i—Ba1—O2iv92.32 (9)Ba1iv—Ti1—Ba172.21 (2)
O8ii—Ba1—O2iv127.44 (9)Ba1xi—Ti1—Ba1129.15 (2)
F1i—Ba1—O2iv121.97 (8)O3—Ti1—Ba1vii69.33 (11)
O8i—Ba1—O2iv64.74 (9)O8—Ti1—Ba1vii36.77 (10)
O6iii—Ba1—O2iv114.92 (9)O9—Ti1—Ba1vii106.96 (10)
F2i—Ba1—O3137.22 (10)O2iv—Ti1—Ba1vii81.08 (10)
O8ii—Ba1—O379.26 (9)O6ii—Ti1—Ba1vii162.31 (10)
F1i—Ba1—O3156.25 (9)F1—Ti1—Ba1vii113.55 (8)
O8i—Ba1—O3113.53 (9)Ti2—Ti1—Ba1vii72.43 (3)
O6iii—Ba1—O3105.26 (9)Ba2viii—Ti1—Ba1vii142.83 (2)
O2iv—Ba1—O353.62 (9)Ba1iv—Ti1—Ba1vii129.71 (2)
F2i—Ba1—O2118.77 (9)Ba1xi—Ti1—Ba1vii69.305 (19)
O8ii—Ba1—O264.96 (9)Ba1—Ti1—Ba1vii85.27 (2)
F1i—Ba1—O2140.74 (9)O9—Ti2—O799.64 (15)
O8i—Ba1—O2160.87 (9)O9—Ti2—O881.93 (14)
O6iii—Ba1—O258.49 (9)O7—Ti2—O896.76 (15)
O2iv—Ba1—O297.08 (10)O9—Ti2—O5viii95.76 (14)
O3—Ba1—O253.11 (9)O7—Ti2—O5viii91.24 (15)
F2i—Ba1—F1v79.10 (8)O8—Ti2—O5viii171.93 (14)
O8ii—Ba1—F1v117.45 (8)O9—Ti2—F290.11 (14)
F1i—Ba1—F1v138.65 (10)O7—Ti2—F2169.87 (15)
O8i—Ba1—F1v110.95 (8)O8—Ti2—F287.25 (13)
O6iii—Ba1—F1v52.43 (8)O5viii—Ti2—F285.02 (13)
O2iv—Ba1—F1v64.80 (8)O9—Ti2—O1vii169.84 (14)
O3—Ba1—F1v63.93 (9)O7—Ti2—O1vii90.23 (15)
O2—Ba1—F1v52.50 (8)O8—Ti2—O1vii94.60 (13)
F2i—Ba1—O4ii120.85 (8)O5viii—Ti2—O1vii86.36 (14)
O8ii—Ba1—O4ii72.44 (9)F2—Ti2—O1vii80.16 (13)
F1i—Ba1—O4ii76.37 (8)O9—Ti2—Ti142.27 (10)
O8i—Ba1—O4ii63.71 (9)O7—Ti2—Ti1101.73 (12)
O6iii—Ba1—O4ii167.70 (9)O8—Ti2—Ti139.68 (10)
O2iv—Ba1—O4ii77.23 (9)O5viii—Ti2—Ti1137.30 (10)
O3—Ba1—O4ii80.02 (9)F2—Ti2—Ti187.30 (9)
O2—Ba1—O4ii120.25 (8)O1vii—Ti2—Ti1133.35 (10)
F1v—Ba1—O4ii138.19 (8)O9—Ti2—Ba2129.57 (10)
F2i—Ba1—O4iii78.86 (8)O7—Ti2—Ba253.89 (11)
O8ii—Ba1—O4iii63.15 (9)O8—Ti2—Ba2136.29 (10)
F1i—Ba1—O4iii65.25 (8)O5viii—Ti2—Ba250.45 (10)
O8i—Ba1—O4iii119.87 (9)F2—Ti2—Ba2117.34 (9)
O6iii—Ba1—O4iii49.05 (8)O1vii—Ti2—Ba258.79 (9)
O2iv—Ba1—O4iii163.91 (8)Ti1—Ti2—Ba2155.29 (3)
O3—Ba1—O4iii126.33 (8)O9—Ti2—Ba1xi100.32 (10)
O2—Ba1—O4iii75.97 (9)O7—Ti2—Ba1xi136.29 (11)
F1v—Ba1—O4iii100.05 (8)O8—Ti2—Ba1xi48.76 (10)
O4ii—Ba1—O4iii118.84 (10)O5viii—Ti2—Ba1xi124.68 (10)
F2i—Ba1—Si1139.22 (7)F2—Ti2—Ba1xi42.83 (8)
O8ii—Ba1—Si163.28 (7)O1vii—Ti2—Ba1xi70.54 (9)
F1i—Ba1—Si1154.35 (6)Ti1—Ti2—Ba1xi69.93 (2)
O8i—Ba1—Si1141.04 (7)Ba2—Ti2—Ba1xi128.99 (3)
O6iii—Ba1—Si184.88 (7)O9—Ti2—Ba2ix127.30 (10)
O2iv—Ba1—Si178.87 (7)O7—Ti2—Ba2ix124.18 (12)
O3—Ba1—Si127.51 (6)O8—Ti2—Ba2ix116.04 (10)
O2—Ba1—Si127.33 (6)O5viii—Ti2—Ba2ix59.40 (10)
F1v—Ba1—Si161.01 (6)F2—Ti2—Ba2ix46.09 (9)
O4ii—Ba1—Si196.16 (6)O1vii—Ti2—Ba2ix46.07 (9)
O4iii—Ba1—Si198.96 (6)Ti1—Ti2—Ba2ix132.66 (3)
F1vi—Ba2—O9vii122.45 (9)Ba2—Ti2—Ba2ix71.98 (2)
F1vi—Ba2—O1viii73.69 (9)Ba1xi—Ti2—Ba2ix68.966 (19)
O9vii—Ba2—O1viii142.97 (10)O9—Ti2—Ba2ii39.26 (10)
F1vi—Ba2—F2ix82.34 (8)O7—Ti2—Ba2ii66.20 (11)
O9vii—Ba2—F2ix91.46 (9)O8—Ti2—Ba2ii105.47 (10)
O1viii—Ba2—F2ix55.54 (9)O5viii—Ti2—Ba2ii76.83 (10)
F1vi—Ba2—O5viii88.87 (9)F2—Ti2—Ba2ii121.74 (9)
O9vii—Ba2—O5viii138.59 (9)O1vii—Ti2—Ba2ii150.30 (10)
O1viii—Ba2—O5viii66.40 (10)Ti1—Ti2—Ba2ii71.94 (3)
F2ix—Ba2—O5viii121.45 (9)Ba2—Ti2—Ba2ii91.88 (2)
F1vi—Ba2—O9vi61.77 (8)Ba1xi—Ti2—Ba2ii139.07 (2)
O9vii—Ba2—O9vi69.48 (10)Ba2ix—Ti2—Ba2ii133.92 (2)
O1viii—Ba2—O9vi135.44 (9)O9—Ti2—Ba2viii39.97 (10)
F2ix—Ba2—O9vi113.94 (9)O7—Ti2—Ba2viii137.20 (12)
O5viii—Ba2—O9vi111.77 (10)O8—Ti2—Ba2viii91.12 (10)
F1vi—Ba2—O7113.79 (9)O5viii—Ti2—Ba2viii82.28 (10)
O9vii—Ba2—O783.67 (9)F2—Ti2—Ba2viii51.62 (9)
O1viii—Ba2—O7122.62 (9)O1vii—Ti2—Ba2viii131.09 (9)
F2ix—Ba2—O7163.24 (9)Ti1—Ti2—Ba2viii60.61 (2)
O5viii—Ba2—O757.40 (9)Ba2—Ti2—Ba2viii132.59 (2)
O9vi—Ba2—O779.38 (9)Ba1xi—Ti2—Ba2viii77.602 (19)
F1vi—Ba2—O6x54.58 (8)Ba2ix—Ti2—Ba2viii88.36 (2)
O9vii—Ba2—O6x72.83 (9)Ba2ii—Ti2—Ba2viii71.14 (2)
O1viii—Ba2—O6x99.59 (9)O1—Si1—O2112.76 (18)
F2ix—Ba2—O6x60.18 (8)O1—Si1—O3108.29 (19)
O5viii—Ba2—O6x143.44 (9)O2—Si1—O3108.07 (18)
O9vi—Ba2—O6x53.77 (9)O1—Si1—O4111.15 (18)
O7—Ba2—O6x132.31 (9)O2—Si1—O4108.97 (18)
F1vi—Ba2—O1vii143.33 (8)O3—Si1—O4107.41 (18)
O9vii—Ba2—O1vii92.52 (9)O1—Si1—Ba1106.78 (13)
O1viii—Ba2—O1vii84.83 (9)O2—Si1—Ba156.52 (12)
F2ix—Ba2—O1vii109.69 (8)O3—Si1—Ba156.42 (13)
O5viii—Ba2—O1vii54.99 (9)O4—Si1—Ba1141.97 (12)
O9vi—Ba2—O1vii132.73 (9)O6—Si2—O5113.93 (18)
O7—Ba2—O1vii54.76 (9)O6—Si2—O7113.43 (19)
O6x—Ba2—O1vii161.13 (9)O5—Si2—O7108.33 (18)
F1vi—Ba2—F2vi55.49 (8)O6—Si2—O4102.77 (17)
O9vii—Ba2—F2vi113.82 (8)O5—Si2—O4109.57 (17)
O1viii—Ba2—F2vi102.72 (8)O7—Si2—O4108.57 (18)
F2ix—Ba2—F2vi137.56 (10)O6—Si2—Ba1xii48.08 (11)
O5viii—Ba2—F2vi59.50 (9)O5—Si2—Ba1xii104.33 (12)
O9vi—Ba2—F2vi53.00 (8)O7—Si2—Ba1xii147.24 (14)
O7—Ba2—F2vi58.30 (9)O4—Si2—Ba1xii61.44 (12)
O6x—Ba2—F2vi94.04 (8)O6—Si2—Ba281.29 (12)
O1vii—Ba2—F2vi102.92 (8)O5—Si2—Ba293.52 (12)
F1vi—Ba2—O5vii122.94 (8)O7—Si2—Ba246.63 (13)
O9vii—Ba2—O5vii94.29 (9)O4—Si2—Ba2151.79 (13)
O1viii—Ba2—O5vii53.52 (9)Ba1xii—Si2—Ba2129.33 (4)
F2ix—Ba2—O5vii52.10 (8)Si1—O1—Ti2ii127.73 (19)
O5viii—Ba2—O5vii88.61 (9)Si1—O1—Ba2vi124.60 (17)
O9vi—Ba2—O5vii159.53 (9)Ti2ii—O1—Ba2vi102.10 (12)
O7—Ba2—O5vii112.13 (8)Si1—O1—Ba2ii108.42 (15)
O6x—Ba2—O5vii110.54 (9)Ti2ii—O1—Ba2ii87.11 (10)
O1vii—Ba2—O5vii57.60 (8)Ba2vi—O1—Ba2ii95.17 (9)
F2vi—Ba2—O5vii147.37 (8)Si1—O2—Ti1v135.8 (2)
F1vi—Ba2—Ti1vi33.81 (6)Si1—O2—Ba1v113.35 (15)
O9vii—Ba2—Ti1vi89.16 (7)Ti1v—O2—Ba1v104.72 (12)
O1viii—Ba2—Ti1vi104.38 (7)Si1—O2—Ba196.15 (14)
F2ix—Ba2—Ti1vi88.14 (6)Ti1v—O2—Ba197.58 (11)
O5viii—Ba2—Ti1vi114.15 (7)Ba1v—O2—Ba1101.25 (11)
O9vi—Ba2—Ti1vi32.88 (6)Si1—O3—Ti1154.9 (2)
O7—Ba2—Ti1vi107.75 (7)Si1—O3—Ba196.08 (15)
O6x—Ba2—Ti1vi33.75 (6)Ti1—O3—Ba1107.94 (14)
O1vii—Ba2—Ti1vi162.03 (6)Si1—O4—Si2131.1 (2)
F2vi—Ba2—Ti1vi60.32 (5)Si1—O4—Ba1vii107.29 (14)
O5vii—Ba2—Ti1vi140.11 (6)Si2—O4—Ba1vii106.12 (15)
O3—Ti1—O898.83 (15)Si1—O4—Ba1xii122.67 (16)
O3—Ti1—O999.20 (15)Si2—O4—Ba1xii91.77 (14)
O8—Ti1—O981.20 (14)Ba1vii—O4—Ba1xii89.87 (8)
O3—Ti1—O2iv86.72 (14)Si2—O5—Ti2vi133.0 (2)
O8—Ti1—O2iv104.34 (14)Si2—O5—Ba2vi127.89 (16)
O9—Ti1—O2iv171.28 (14)Ti2vi—O5—Ba2vi96.77 (12)
O3—Ti1—O6ii94.81 (15)Si2—O5—Ba2ii102.00 (14)
O8—Ti1—O6ii160.30 (14)Ti2vi—O5—Ba2ii89.00 (11)
O9—Ti1—O6ii82.64 (13)Ba2vi—O5—Ba2ii91.39 (9)
O2iv—Ti1—O6ii90.52 (14)Si2—O6—Ti1vii135.54 (19)
O3—Ti1—F1167.72 (15)Si2—O6—Ba1xii107.24 (15)
O8—Ti1—F188.87 (13)Ti1vii—O6—Ba1xii99.01 (12)
O9—Ti1—F191.39 (12)Si2—O6—Ba2x120.88 (15)
O2iv—Ti1—F182.08 (12)Ti1vii—O6—Ba2x91.61 (11)
O6ii—Ti1—F180.32 (12)Ba1xii—O6—Ba2x93.93 (9)
O3—Ti1—Ti2102.80 (12)Si2—O7—Ti2155.3 (2)
O8—Ti1—Ti242.44 (10)Si2—O7—Ba2109.65 (16)
O9—Ti1—Ti238.78 (10)Ti2—O7—Ba294.79 (13)
O2iv—Ti1—Ti2146.09 (11)Ti1—O8—Ti297.88 (14)
O6ii—Ti1—Ti2120.40 (9)Ti1—O8—Ba1vii119.91 (14)
F1—Ti1—Ti289.34 (8)Ti2—O8—Ba1vii123.15 (14)
O3—Ti1—Ba2viii136.63 (12)Ti1—O8—Ba1xi108.04 (14)
O8—Ti1—Ba2viii106.06 (10)Ti2—O8—Ba1xi99.95 (12)
O9—Ti1—Ba2viii51.96 (9)Ba1vii—O8—Ba1xi105.68 (10)
O2iv—Ti1—Ba2viii119.48 (9)Ti2—O9—Ti198.95 (14)
O6ii—Ti1—Ba2viii54.65 (9)Ti2—O9—Ba2ii115.82 (14)
F1—Ti1—Ba2viii48.09 (8)Ti1—O9—Ba2ii118.79 (14)
Ti2—Ti1—Ba2viii75.16 (3)Ti2—O9—Ba2viii115.68 (14)
O3—Ti1—Ba1iv114.94 (12)Ti1—O9—Ba2viii95.16 (12)
O8—Ti1—Ba1iv133.77 (10)Ba2ii—O9—Ba2viii110.52 (10)
O9—Ti1—Ba1iv120.50 (10)Ti1—F1—Ba2viii98.10 (10)
O2iv—Ti1—Ba1iv50.83 (9)Ti1—F1—Ba1xi103.58 (11)
O6ii—Ti1—Ba1iv49.05 (9)Ba2viii—F1—Ba1xi121.85 (10)
F1—Ti1—Ba1iv53.56 (8)Ti1—F1—Ba1iv93.72 (10)
Ti2—Ti1—Ba1iv140.85 (3)Ba2viii—F1—Ba1iv95.45 (8)
Ba2viii—Ti1—Ba1iv70.507 (19)Ba1xi—F1—Ba1iv135.16 (10)
O3—Ti1—Ba1xi138.61 (12)Ti2—F2—Ba1xi106.44 (11)
O8—Ti1—Ba1xi44.63 (10)Ti2—F2—Ba2ix102.91 (11)
O9—Ti1—Ba1xi93.75 (10)Ba1xi—F2—Ba2ix102.85 (10)
O2iv—Ti1—Ba1xi85.86 (10)Ti2—F2—Ba2viii99.00 (11)
O6ii—Ti1—Ba1xi125.90 (10)Ba1xi—F2—Ba2viii112.55 (9)
F1—Ti1—Ba1xi45.68 (8)Ba2ix—F2—Ba2viii130.56 (10)
Ti2—Ti1—Ba1xi65.36 (3)
Symmetry codes: (i) x+1, y1/2, z+1/2; (ii) x+1/2, y1/2, z; (iii) x, y1/2, z+1/2; (iv) x+1/2, y, z+1/2; (v) x1/2, y, z+1/2; (vi) x1/2, y+3/2, z+1; (vii) x+1/2, y+1/2, z; (viii) x+1/2, y+3/2, z+1; (ix) x+1, y+2, z+1; (x) x, y+2, z+1; (xi) x+1, y+1/2, z+1/2; (xii) x, y+1/2, z+1/2.

Experimental details

Crystal data
Chemical formulaBa2Ti2Si2O9F2
Mr608.66
Crystal system, space groupOrthorhombic, Pbca
Temperature (K)298
a, b, c (Å)8.7350 (17), 10.832 (2), 18.769 (4)
V3)1775.9 (6)
Z8
Radiation typeMo Kα
µ (mm1)10.83
Crystal size (mm)0.12 × 0.11 × 0.09
Data collection
DiffractometerRigaku AFC-8S Mercury CCD
diffractometer
Absorption correctionMulti-scan
(Jacobson, 1998)
Tmin, Tmax0.303, 0.376
No. of measured, independent and
observed [I > 2σ(I)] reflections
13481, 1573, 1539
Rint0.034
(sin θ/λ)max1)0.596
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.026, 0.058, 1.41
No. of reflections1573
No. of parameters155
Δρmax, Δρmin (e Å3)1.05, 1.18

Computer programs: CrystalClear (Molecular Structure Corporation & Rigaku, 2001), SHELXTL (Version 6.10; Sheldrick, 2008), DIAMOND (Brandenburg, 1999).

Selected bond lengths (Å) top
Ba1—F2i2.647 (3)Ba2—O5vii3.242 (3)
Ba1—O8ii2.816 (3)Ti1—O31.855 (3)
Ba1—F1i2.840 (3)Ti1—O81.863 (3)
Ba1—O8i2.851 (3)Ti1—O91.968 (3)
Ba1—O6iii2.863 (3)Ti1—O2iv1.979 (3)
Ba1—O2iv2.914 (3)Ti1—O6ii2.006 (3)
Ba1—O32.925 (4)Ti1—F12.029 (3)
Ba1—O22.929 (3)Ti2—O91.832 (3)
Ba1—F1v3.019 (3)Ti2—O71.888 (3)
Ba1—O4ii3.164 (3)Ti2—O81.969 (3)
Ba1—O4iii3.230 (3)Ti2—O5viii1.973 (3)
Ba2—F1vi2.713 (3)Ti2—F21.989 (3)
Ba2—O9vii2.752 (3)Ti2—O1vii2.031 (3)
Ba2—O1viii2.773 (3)Si1—O11.601 (3)
Ba2—F2ix2.783 (3)Si1—O21.612 (3)
Ba2—O5viii2.810 (3)Si1—O31.621 (3)
Ba2—O9vi2.854 (3)Si1—O41.641 (3)
Ba2—O72.934 (4)Si2—O61.607 (3)
Ba2—O6x2.945 (3)Si2—O51.614 (3)
Ba2—O1vii3.100 (3)Si2—O71.623 (3)
Ba2—F2vi3.178 (3)Si2—O41.658 (3)
Symmetry codes: (i) x+1, y1/2, z+1/2; (ii) x+1/2, y1/2, z; (iii) x, y1/2, z+1/2; (iv) x+1/2, y, z+1/2; (v) x1/2, y, z+1/2; (vi) x1/2, y+3/2, z+1; (vii) x+1/2, y+1/2, z; (viii) x+1/2, y+3/2, z+1; (ix) x+1, y+2, z+1; (x) x, y+2, z+1.
 

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