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ISSN: 2056-9890

A cubic calcium oxynitrido-silicate, Ca2.89Si2N1.76O4.24

aSchool of Engineering, Linné University, Växjö, S-351 95 Växjö, Sweden, and bDepartment of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, S-106 91 Stockholm, Sweden
*Correspondence e-mail: lars.eriksson@mmk.su.se

(Received 21 September 2011; accepted 14 October 2011; online 29 October 2011)

The title compound, tricalcium oxynitride silicate, with composition Ca3-xSi2N2-2xO4+2x (x ≃ 0.12), is a perovskite-related calcium oxynitrido silicate containing isolated oxynitrido silicate 12-rings. The N atoms are statistically disordered with O atoms (occupancy ratio N:O = 0.88:0.12) and occupy the bridging positions in the 12 ring oxynitrido silicate anion, while the remaining O atoms are located at the terminal positions of the Si(O,N)4 tetrahedra. The majority of the Ca2+ cations fill the channels along [100] in the packing of the 12-ring anions. The rest of these cations are located at several positions, with partial occupancy, in channels along the body diagonals.

Related literature

For a closely related silicate, as well as a germanate, see: Fischer & Tillmanns (1984[Fischer, R. X. & Tillmanns, E. (1984). Z. Kristallogr. 166, 245-256.]) and for a more distantly related calcium aluminate, see: Mondal & Jeffery (1975[Mondal, P. & Jeffery, J. W. (1975). Acta Cryst. B31, 689-697.])

Experimental

Crystal data
  • Ca2.89Si2N1.76O4.24

  • Mr = 264.65

  • Cubic, [P a \overline 3]

  • a = 15.0626 (1) Å

  • V = 3417.45 (4) Å3

  • Z = 24

  • Mo Kα radiation

  • μ = 3.18 mm−1

  • T = 293 K

  • 0.10 × 0.06 × 0.02 mm

Data collection
  • Oxford Diffraction XcaliburIII with Sapphire-3 CCD diffractometer

  • Absorption correction: multi-scan (CrysAlis RED; Oxford Diffraction, 2008[Oxford Diffraction. (2008). CrysAlis CCD and CrysAlis RED. Oxford Diffraction Ltd, Abingdon, England.]) Tmin = 0.67, Tmax = 0.94

  • 30793 measured reflections

  • 1982 independent reflections

  • 1779 reflections with I > 2s(I)

  • Rint = 0.027

Refinement
  • R[F2 > 2σ(F2)] = 0.032

  • wR(F2) = 0.069

  • S = 1.22

  • 1982 reflections

  • 113 parameters

  • Δρmax = 0.87 e Å−3

  • Δρmin = −0.76 e Å−3

Table 1
Selected bond lengths (Å)

Si1—O4 1.6245 (15)
Si1—O3 1.6476 (14)
Si1—N2/O2 1.6788 (18)
Si1—N1/O1 1.6958 (17)
Si2—O6 1.6341 (15)
Si2—O5 1.6485 (15)
Si2—N1/O1i 1.6899 (17)
Si2—N2/O2 1.6942 (18)
Symmetry code: (i) [-y+{\script{1\over 2}}, z-{\script{1\over 2}}, x+1].

Data collection: CrysAlis CCD (Oxford Diffraction, 2008[Oxford Diffraction. (2008). CrysAlis CCD and CrysAlis RED. Oxford Diffraction Ltd, Abingdon, England.]); cell refinement: CrysAlis RED (Oxford Diffraction, 2008[Oxford Diffraction. (2008). CrysAlis CCD and CrysAlis RED. Oxford Diffraction Ltd, Abingdon, England.]); data reduction: CrysAlis RED; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); molecular graphics: DIAMOND (Brandenburg, 2001[Brandenburg, K. (2001). DIAMOND. Crystal Impact GbR, Bonn, Germany.]); software used to prepare material for publication: PLATON (Spek, 2009[Spek, A. L. (2009). Acta Cryst. D65, 148-155.]) and SHELXL97.

Supporting information


Comment top

The title compound is a crystalline component formed in the melts of oxynitrido glasses, studied at our department. The title compound calcium oxynitrido-silicate contains isolated 12-ring anions with the ideal composition Ca3 - xSi2N2–2xO4 + 2x where the title compound have x 0.12. It should be emphasized that x=0 do not indicate an end member of a possible solid solution series of compounds. The nitrogen atoms in the anions occupies mainly the ring positions in the 12 ring while the oxygen atoms mainly occupy the apex positions. A figure of the oxynitrido-silicate anion is shown in Fig. 1. In Fig. 2 a simplified packing is shown where the arrangement of Ca atoims in channels along <100> as well as the disordered arrangement along the <111> directions. 56 Ca atoms in each unit cell fills channels along <100> in the packing of the 12-ring anions while the rest of the Ca positions are located in channels along <111> and show tendencies to be disordered. The split positions of the Ca cations along the <111> can be viewed as a consequence of the implied Pa-3 symmetry. Whether the space group should better be P213 or even P212121 with cubic twinning is unfortunately not possible to determine, neither from systematic reflection conditions nor from investigations of the s.u. of the cell parameters. No One can refine orthorhombic unit-cell parameters but if one should beleive the e.s.d.'s is more of an open question. We choose to describe the structure with highest possible symmetry but at the price of some disorder. Similar arrangements of cations and ring formed anions are found in the structurally related compounds K4SrGe3O9 and Na4CaSi3O9 (Fischer & Tillmanns, 1984).

Related literature top

For a related pseudo isomorphic silicate as well as a germanate, see: Fischer & Tillmanns (1984) and for a more distantly related calcium aluminate, see: Mondal & Jeffery (1975)

Experimental top

The title compound was obtained by slow cooling of a melt with the nominal composition Ca1.71Si2O1.71N2.67 from 1700° C by 1° C / min in a graphite furnace.

Refinement top

In order to match the refined Ca composition the N1 and N2 position were mixed occupied by 88° N and 12°O. Attempts to refine the N/O ratio from the X-ray diffraction data failed using the present single-crystal data as a consequence of the close resemblance of the atomic form factors of N and O. The occupancy factors of the Calcium ions did converge to the composition reported in the title and was fully consistent with results from EDS analyses giving the ratio Ca/Si = 0.59 (1). The refined Ca content 2.88 and 2 Si give the Ca/Si = 0.59. It must be emphasized that the precise occupation of Ca atoms are heavily dependent on the precise model used. Including a larger number of Ca atoms, one could refine the model slightly closer to the ideal composition Ca3Si2O4N2.

Computing details top

Data collection: CrysAlis CCD (Oxford Diffraction, 2008); cell refinement: CrysAlis RED (Oxford Diffraction, 2008); data reduction: CrysAlis RED (Oxford Diffraction, 2008); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2001); software used to prepare material for publication: PLATON (Spek, 2009) and SHELXL97 (Sheldrick, 2008).

Figures top
[Figure 1] Fig. 1. The oxynitrido-silicate anion of the title compound (I) with the unique atoms of the oxynitrido-silicate anion labelled. Displacement ellipsoids drawn at 50% probability.
[Figure 2] Fig. 2. Stereoview of the unitcell viewed approximately along [100] with the oxynitrido-silicate anions marked with red colour and the Ca atoms ffwith blue colour. The disordered arrays of Ca atoms along the <111> shown by a solid rod.
tricalcium oxynitride silicate top
Crystal data top
Ca2.89Si2N1.76O4.24Dx = 3.087 Mg m3
Mr = 264.65Mo Kα radiation, λ = 0.71073 Å
Cubic, Pa3Cell parameters from 19622 reflections
Hall symbol: -P 2ac 2ab 3θ = 3.8–32.2°
a = 15.0626 (1) ŵ = 3.18 mm1
V = 3417.45 (4) Å3T = 293 K
Z = 24Block, colourless
F(000) = 31580.10 × 0.06 × 0.02 mm
Data collection top
Oxford Diffraction XcaliburIII with Sapphire-3 CCD
diffractometer
1982 independent reflections
Radiation source: fine-focus sealed tube1779 reflections with I > 2s(I)
Graphite monochromatorRint = 0.027
Detector resolution: 16.5467 pixels mm-1θmax = 32.3°, θmin = 3.8°
ω scans at different ϕh = 2218
Absorption correction: multi-scan
(CrysAlis RED; Oxford Diffraction, 2008)
k = 1821
Tmin = 0.67, Tmax = 0.94l = 2221
30793 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)] = 0.032 w = 1/[σ2(Fo2) + (0.026P)2 + 5.7834P]
where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.069(Δ/σ)max = 0.001
S = 1.22Δρmax = 0.87 e Å3
1982 reflectionsΔρmin = 0.76 e Å3
113 parametersExtinction correction: SHELXL97 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
0 restraintsExtinction coefficient: 0.00048 (5)
Crystal data top
Ca2.89Si2N1.76O4.24Z = 24
Mr = 264.65Mo Kα radiation
Cubic, Pa3µ = 3.18 mm1
a = 15.0626 (1) ÅT = 293 K
V = 3417.45 (4) Å30.10 × 0.06 × 0.02 mm
Data collection top
Oxford Diffraction XcaliburIII with Sapphire-3 CCD
diffractometer
1982 independent reflections
Absorption correction: multi-scan
(CrysAlis RED; Oxford Diffraction, 2008)
1779 reflections with I > 2s(I)
Tmin = 0.67, Tmax = 0.94Rint = 0.027
30793 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.032113 parameters
wR(F2) = 0.0690 restraints
S = 1.22Δρmax = 0.87 e Å3
1982 reflectionsΔρmin = 0.76 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*/UeqOcc. (<1)
Si10.00530 (3)0.27221 (3)0.76315 (3)0.00633 (9)
Si20.01658 (3)0.24358 (3)0.98439 (3)0.00567 (9)
N10.01861 (12)0.37791 (11)0.72676 (13)0.0176 (3)0.88
O10.01861 (12)0.37791 (11)0.72676 (13)0.0176 (3)0.12
N20.00891 (13)0.26556 (13)0.87435 (11)0.0193 (4)0.88
O20.00891 (13)0.26556 (13)0.87435 (11)0.0193 (4)0.12
O30.09048 (10)0.21494 (9)0.72534 (9)0.0131 (3)
O40.09065 (10)0.23612 (10)0.72964 (10)0.0160 (3)
O50.01845 (10)0.33802 (10)1.02719 (10)0.0147 (3)
O60.04423 (10)0.15759 (10)1.01040 (10)0.0153 (3)
Ca10.12893 (2)0.37107 (2)1.12893 (2)0.01028 (12)
Ca20.11371 (3)0.38333 (3)0.90382 (3)0.01162 (8)
Ca30.13964 (3)0.13071 (3)0.85405 (3)0.01601 (9)
Ca40.24330 (14)0.25670 (14)0.74330 (14)0.0094 (6)*0.1715 (6)
Ca50.1757 (2)0.3243 (2)0.6757 (2)0.0094 (2)*0.140 (2)
Ca60.15523 (5)0.34477 (5)0.65523 (5)0.0094 (2)*0.670 (3)
Ca70.1254 (9)0.3746 (9)0.6254 (9)0.0094 (2)*0.043 (3)
Ca80.1031 (7)0.3969 (7)0.6031 (7)0.0094 (2)*0.076 (2)
Ca90.0819 (5)0.4181 (5)0.5819 (5)0.0094 (2)*0.086 (3)
Ca100.0572 (3)0.4428 (3)0.5572 (3)0.0094 (2)*0.099 (2)
Ca110.0166 (4)0.4834 (4)0.5166 (4)0.0094 (2)*0.095 (3)
Ca120.00000.50000.50000.0094 (2)*0.603 (6)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Si10.0077 (2)0.0061 (2)0.0052 (2)0.00013 (16)0.00028 (15)0.00047 (15)
Si20.00564 (19)0.0064 (2)0.0049 (2)0.00030 (16)0.00068 (15)0.00020 (16)
N10.0206 (8)0.0063 (7)0.0260 (9)0.0011 (6)0.0043 (7)0.0004 (6)
O10.0206 (8)0.0063 (7)0.0260 (9)0.0011 (6)0.0043 (7)0.0004 (6)
N20.0240 (9)0.0274 (9)0.0066 (7)0.0007 (7)0.0010 (6)0.0004 (6)
O20.0240 (9)0.0274 (9)0.0066 (7)0.0007 (7)0.0010 (6)0.0004 (6)
O30.0149 (6)0.0105 (6)0.0140 (6)0.0035 (5)0.0042 (5)0.0008 (5)
O40.0150 (6)0.0162 (7)0.0169 (7)0.0055 (5)0.0065 (5)0.0014 (5)
O50.0174 (7)0.0124 (6)0.0144 (6)0.0057 (5)0.0035 (5)0.0062 (5)
O60.0157 (7)0.0132 (6)0.0170 (7)0.0063 (5)0.0040 (5)0.0008 (5)
Ca10.01028 (12)0.01028 (12)0.01028 (12)0.00048 (12)0.00048 (12)0.00048 (12)
Ca20.01262 (17)0.00917 (16)0.01306 (17)0.00006 (12)0.00140 (13)0.00004 (12)
Ca30.01781 (19)0.01586 (19)0.01435 (18)0.00563 (14)0.00307 (14)0.00105 (14)
Geometric parameters (Å, º) top
Si1—O41.6245 (15)Si2—O61.6341 (15)
Si1—O31.6476 (14)Si2—O51.6485 (15)
Si1—N21.6788 (18)Si2—N1i1.6899 (17)
Si1—N11.6958 (17)Si2—N21.6942 (18)
O4—Si1—O3114.22 (8)O6—Si2—N1i109.58 (9)
O4—Si1—N2108.60 (9)O5—Si2—N1i108.13 (9)
O3—Si1—N2106.76 (9)O6—Si2—N2110.56 (9)
O4—Si1—N1108.59 (9)O5—Si2—N2101.08 (9)
O3—Si1—N1106.72 (8)O1i—Si2—N2113.07 (9)
N2—Si1—N1112.00 (10)N1i—Si2—N2113.07 (9)
O6—Si2—O5114.26 (8)Si2ii—N1—Si1142.98 (12)
O6—Si2—O1i109.58 (9)Si1—N2—Si2171.87 (14)
O5—Si2—O1i108.13 (9)
N2—Si1—N1—Si2ii46.7 (2)
Symmetry codes: (i) y+1/2, z1/2, x+1; (ii) z1, x+1/2, y+1/2.

Experimental details

Crystal data
Chemical formulaCa2.89Si2N1.76O4.24
Mr264.65
Crystal system, space groupCubic, Pa3
Temperature (K)293
a (Å)15.0626 (1)
V3)3417.45 (4)
Z24
Radiation typeMo Kα
µ (mm1)3.18
Crystal size (mm)0.10 × 0.06 × 0.02
Data collection
DiffractometerOxford Diffraction XcaliburIII with Sapphire-3 CCD
diffractometer
Absorption correctionMulti-scan
(CrysAlis RED; Oxford Diffraction, 2008)
Tmin, Tmax0.67, 0.94
No. of measured, independent and
observed [I > 2s(I)] reflections
30793, 1982, 1779
Rint0.027
(sin θ/λ)max1)0.752
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.032, 0.069, 1.22
No. of reflections1982
No. of parameters113
Δρmax, Δρmin (e Å3)0.87, 0.76

Computer programs: CrysAlis CCD (Oxford Diffraction, 2008), CrysAlis RED (Oxford Diffraction, 2008), SHELXS97 (Sheldrick, 2008), DIAMOND (Brandenburg, 2001), PLATON (Spek, 2009) and SHELXL97 (Sheldrick, 2008).

Selected bond lengths (Å) top
Si1—O41.6245 (15)Si2—O61.6341 (15)
Si1—O31.6476 (14)Si2—O51.6485 (15)
Si1—N21.6788 (18)Si2—N1i1.6899 (17)
Si1—N11.6958 (17)Si2—N21.6942 (18)
Symmetry code: (i) y+1/2, z1/2, x+1.
 

Acknowledgements

This work was supported by a grant from the Swedish Research Council and by the Faculty of Natural Sciences at Stockholm University.

References

First citationBrandenburg, K. (2001). DIAMOND. Crystal Impact GbR, Bonn, Germany.  Google Scholar
First citationFischer, R. X. & Tillmanns, E. (1984). Z. Kristallogr. 166, 245–256.  CrossRef CAS Web of Science Google Scholar
First citationMondal, P. & Jeffery, J. W. (1975). Acta Cryst. B31, 689–697.  CrossRef CAS IUCr Journals Web of Science Google Scholar
First citationOxford Diffraction. (2008). CrysAlis CCD and CrysAlis RED. Oxford Diffraction Ltd, Abingdon, England.  Google Scholar
First citationSheldrick, G. M. (2008). Acta Cryst. A64, 112–122.  Web of Science CrossRef CAS IUCr Journals Google Scholar
First citationSpek, A. L. (2009). Acta Cryst. D65, 148–155.  Web of Science CrossRef CAS IUCr Journals Google Scholar

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ISSN: 2056-9890
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