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ISSN: 2056-9890
Volume 72| Part 2| February 2016| Pages 249-252

Rietveld refinement of the crystal structures of Rb2XSi5O12 (X = Ni, Mn)

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aMaterials and Engineering Research Institute (MERI), Sheffield Hallam University, Sheffield S1 1WB, England, bSchool of Earth, Atmospheric and Environmental Sciences, University of Manchester, Manchester M13 9PL, England, and cASTeC, Sci-Tech Daresbury Laboratory, Science and Technology Facilities Council, Warrington WA4 4AD, England
*Correspondence e-mail: anthony.bell@shu.ac.uk

Edited by A. Van der Lee, Université de Montpellier II, France (Received 18 December 2015; accepted 21 January 2016; online 27 January 2016)

The synthetic leucite silicate framework mineral analogues Rb2XSi5O12 {X = Ni [dirubidium nickel(II) penta­silicate] and Mn [dirubidium manganese(II) penta­silicate]} have been prepared by high-temperature solid-state synthesis. The results of Rietveld refinements, using X-ray powder diffraction data collected using Cu Kα X-rays, show that the title compounds crystallize in the space group Pbca and adopt the cation-ordered structure of Cs2CdSi5O12 and other leucites. The structures consist of tetra­hedral SiO4 and XO4 units sharing corners to form a partially substituted silicate framework. Extraframework Rb+ cations sit in channels in the framework. All atoms occupy the 8c general position for this space group. In these refined structures, silicon and X atoms are ordered onto separate tetra­hedrally coordinated sites (T-sites). However, the Ni displacement parameter and the Ni—O bond lengths suggest that for the X = Ni sample, there may actually be some T-site cation disorder.

1. Chemical context

Synthetic analogues of the silicate framework minerals leucite KAlSi2O6 (Mazzi et al., 1976[Mazzi, F., Galli, E. & Gottardi, G. (1976). Am. Mineral. 61, 108-115.]) and pollucite CsAlSi2O6 (Dimitrijevic et al., 1991[Dimitrijevic, R., Dondur, V. & Petranovic, N. (1991). J. Solid State Chem. 95, 335-345.]) can be prepared with the general formulae ABSi2O6 and A2CSi5O12. A is an alkali metal cation (K, Rb, Cs), B is a trivalent cation (Al, B, Fe3+) and C is a divalent cation (Be, Mg, Mn, Fe2+, Co, Ni, Cu, Zn, Cd). The title compounds are leucite analogues with A = Rb and C = Ni and Mn, these structures are in the space group Pbca and are isostructural with Cs2CdSi5O12 (Bell et al., 1994b[Bell, A. M. T., Redfern, S. A. T., Henderson, C. M. B. & Kohn, S. C. (1994b). Acta Cryst. B50, 560-566.]).

These leucite structures all have the same topology, a silicate framework structure with B or C cations partially substituting on the tetra­hedrally coordinated silicon sites (T-sites). A cations sit in the extraframework channels, these extraframework cations can be removed by ion exchange which makes them of technological inter­est as a possible storage medium for radioactive Cs from nuclear waste (Gatta et al., 2008[Gatta, G. D., Rotiroti, N., Fisch, M., Kadiyski, M. & Armbruster, T. (2008). Phys. Chem. Miner. 35, 521-533.]).

2. Structural commentary

For the X = Ni refinement, the Ni site isotropic temperature factor was larger than expected [Biso = 7.5 (9) Å2]. Also the mean Ni—O bond length for the NiO4 tetra­hedron is 1.90 (2) Å, shorter than that seen in tetra­hedrally coordinated NiO4 units. NiCr2O4 has the cubic spinel structure with Ni in tetra­hedral coordination. A single-crystal structure refinement (Crottaz et al., 1997[Crottaz, O., Kubel, F. & Schmid, H. (1997). J. Mater. Chem. 7, 143-146.]) gives the Ni—O distance as 1.967 (3) Å. An EXAFS/XANES study (Farges et al., 2001[Farges, F., Brown, G. E., Petit, P.-E. & Munoz, M. (2001). Geochim. Cosmochim. Acta, 65, 1665-1678.]) gives the Ni—O distance as 1.96 (1) Å. The mean Si—O bond length for the SiO4 tetra­hedra in the title structure is 1.643 (18) Å, which is slightly larger than the range of Si—O distances for silicates [1.59–1.63 Å; Inter­national Tables for X-ray Crystallography (1975, Vol. III, Table 4.1.1)]. These differences in the Ni—O and Si—O distances suggest some possible T-site cation disorder with some Si on the Ni site. A future higher quality neutron/synchrotron X-ray powder diffraction study may show if there really is Ni/Si T-site cation disorder.

Fig. 1[link] shows the Rietveld difference plot for Rb2NiSi5O12. The crystal structure of Rb2NiSi5O12 is displayed in Fig. 2[link] and consists of a framework of corner-sharing tetra­hedral SiO4 and NiO4 units, and Rb+ cations sitting in the extraframework channels.

[Figure 1]
Figure 1
Rietveld difference plot for the single-phase refinement of Rb2NiSi5O12. The red, blue and green lines show, respectively, the observed, calculated and difference plots. Calculated Bragg reflection positions are indicated by crosses.
[Figure 2]
Figure 2
The crystal structure of Rb2NiSi5O12. Green spheres show Rb cations, blue polyhedra show SiO4 units, pink polyhedra show NiO4 units and red spheres represent O atoms.

For the X = Mn refinement, unlike in the X = Ni sample, the mean Mn—O distance is 2.02 (1) Å. This is in agreement with the mean Mn—O distance for Cs2MnSi5O12 (1.98 (3) Å; Bell & Henderson, 1996[Bell, A. M. T. & Henderson, C. M. B. (1996). Acta Cryst. C52, 2132-2139.]). This would suggest that this structure has complete T-site cation ordering. However, the isotropic temperature factors for the Mn site and the O sites could not be refined to chemically sensible positive values, so these were both fixed at Biso = 0.1 Å2. This refinement was done assuming that Mn was present as Mn2+ and that all sites were fully occupied. If some or all of the Mn atoms were present with a higher oxidation state, then this could account for the problem with refining these temperature factors. However, a higher quality neutron/synchrotron X-ray powder diffraction study may also be needed for a more precise determination of the state of Mn in this structure.

Fig. 3[link] shows the Rietveld difference plot for Rb2MnSi5O12. The crystal structure of Rb2MnSi5O12 is displayed in Fig. 4[link] and consists of a framework of corner-sharing tetra­hedral SiO4 and MnO4 units; Rb cations sit in the extraframework channels. Note how inclusion of the larger Mn cation in the silicate framework compared to Ni causes the central channel of the crystal structure to be slightly more distorted for Rb2MnSi5O12 (Fig. 4[link]) compared to Rb2NiSi5O12 (Fig. 2[link]).

[Figure 3]
Figure 3
Rietveld difference plot for the single-phase refinement of Rb2MnSi5O12. The red, blue and green lines show, respectively, the observed, calculated and difference plots. Calculated Bragg reflection positions are indicated by crosses.
[Figure 4]
Figure 4
The crystal structure of Rb2MnSi5O12. Green spheres show Rb cations, blue polyhedra show SiO4 units, purple polyhedra show MnO4 units and red spheres represent O atoms.

3. Database survey

Many different leucite analogue crystal structures are known at ambient temperature. Table 1[link] gives compositions, space groups, lattice parameters, and references for some known ambient temperature leucite crystal structures. In addition, a high-temperature structure for Cs2ZnSi5O12 in the space group Pa[\overline{3}] has been reported above 566 K (Bell & Henderson, 2012[Bell, A. M. T. & Henderson, C. M. B. (2012). Mineral. Mag. 76, 1257-1280.]).

Table 1
Crystal structure parameters (Å°) for room-temperature leucite analogues

Stoichiometry SG a b c β V
K2MgSi5O12a Ia[\overline{3}]d 13.4190 (1) 13.4190 (1) 13.4190 (1) 90 2416.33 (5)
K2MgSi5O12a P21/c 13.168 (5) 13.652 (1) 13.072 (5) 91.69 (5) 2348 (2)
Cs2CdSi5O12b Pbca 13.6714 (1) 13.8240 (1) 13.8939 (1) 90 2625.83 (6)
Cs2CuSi5O12c Pbca 13.58943 (6) 13.57355 (5) 13.62296 (4) 90 2512.847 (13)
Cs2CuSi5O12c Ia[\overline{3}]d 13.6322 (4) 13.6322 (4) 13.6322 (4) 90 2533.4 (2)
Cs2MgSi5O12d Pbca 13.6371 (5) 13.6689 (5) 13.7280 (5) 90 2559.0 (2)
Rb2MgSi5O12d Pbca 13.422 (1) 13.406 (1) 13.730 (1) 90 2470.6 (4)
Cs2ZnSi5O12d Pbca 13.6415 (9) 13.6233 (8) 13.6653 (9) 90 2539.6 (3)
Rb2CdSi5O12e Pbca 13.4121 (1) 13.6816 (1) 13.8558 (1) 90 2542.51 (5)
Cs2MnSi5O12e Pbca 13.6878 (3) 13.7931 (3) 13.7575 (3) 90 2597.4 (2)
Cs2CoSi5O12e Pbca 13.6487 (4) 13.7120 (4) 13.6828 (4) 90 2560.7 (2)
Cs2NiSi5O12e Pbca 13.6147 (3) 13.6568 (5) 13.6583 (5) 90 2539.5 (1)
Rb2ZnSi5O12f Ia[\overline{3}]d 13.4972 (1) 13.4972 (1) 13.4972 (1) 90 2458.86 (3)
KFeSi2O6g I41/a 13.2207 (3) 13.2207 (3) 13.9464 (3) 90 2437.6 (2)
RbFeSi2O6g I41/a 13.4586 (1) 13.4586 (1) 13.9380 (1) 90 2524.63 (5)
CsFeSi2O6g Ia[\overline{3}]d 13.8542 (1) 13.8542 (1) 13.8542 (1) 90 2653.98 (3)
CsBSi2O6h I41/a 13.019 (2) 13.019 (2) 12.899 (3) 90 2186 (1)
CsAlSi2O6i Ia[\overline{3}]d 13.647 (3) 13.647 (3) 13.647 (3) 90 2541.6 (6)
KAlSi2O6j I41/a 13.09 (1) 13.09 (1) 13.75 (1) 90 2356 (5)
Cs0.814B1.092Si1.977O6k Ia-3d 13.009 (8) 13.009 (8) 13.009 (8) 90 2202 (1)
Rb2MgSi5O12l Ia[\overline{3}]d 13.530 (1) 13.530 (1) 13.530 (1) 90 2476.8 (2)
Cs2BeSi5O12m Ia[\overline{3}]d 13.406 (1) 13.406 (1) 13.406 (1) 90 2409.3 (2)
Notes: SG = space group; all α and γ angles = 90°; (a) Bell et al. (1994a[Bell, A. M. T. & Henderson, C. M. B. (1994a). Acta Cryst. C50, 984-986.]); (b) Bell et al. (1994b[Bell, A. M. T. & Henderson, C. M. B. (1994b). Acta Cryst. C50, 1531-1536.]); (c) Bell et al. (2010[Bell, A. M. T., Knight, K. S., Henderson, C. M. B. & Fitch, A. N. (2010). Acta Cryst. B66, 51-59.]); (d) Bell & Henderson (2009[Bell, A. M. T. & Henderson, C. M. B. (2009). Acta Cryst. B65, 435-444.]); (e) Bell & Henderson (1996[Bell, A. M. T. & Henderson, C. M. B. (1996). Acta Cryst. C52, 2132-2139.]); (f) Bell & Henderson (1994a[Bell, A. M. T. & Henderson, C. M. B. (1994a). Acta Cryst. C50, 984-986.]); (g) Bell & Henderson (1994b[Bell, A. M. T. & Henderson, C. M. B. (1994b). Acta Cryst. C50, 1531-1536.]); (h) Agakhanov et al. (2012[Agakhanov, A. A., Pautov, L. A., Karpenko, V. Y., Sokolova, E. & Hawthorne, F. C. (2012). Can. Mineral. 50, 523-529.]); (i) Dimitrijevic et al. (1991[Dimitrijevic, R., Dondur, V. & Petranovic, N. (1991). J. Solid State Chem. 95, 335-345.]); (j) Mazzi et al. (1976[Mazzi, F., Galli, E. & Gottardi, G. (1976). Am. Mineral. 61, 108-115.]); (k) Bubnova et al. (2004[Bubnova, R. S., Stepanov, N. K., Levin, A. A., Filatov, S. K., Paufler, P. & Meyer, D. C. (2004). Solid State Sci. 6, 629-637.]); (l) Torres-Martinez & West (1986[Torres-Martinez, L. M. & West, A. R. (1986). Z. Kristallogr. 175, 1-7.]); (m) Torres-Martinez et al. (1984[Torres-Martinez, L. M., Gard, J. A., Howie, R. A. & West, A. R. (1984). J. Solid State Chem. 51, 100-103.]).

4. Synthesis and crystallization

The samples were made from stoichiometric mixtures of Rb2CO3, SiO2 and NiO (X = Ni) or MnO (X = Mn). These mixtures were ground together and then heated overnight at 873 K to decompose the carbonates, then melted in platinum crucibles at 1573 K for 1.5 h (X = Ni) or 1673 K for 2 h (X = Mn) before quenching to form glasses. The glasses were dry-crystallized at ambient pressure and 1193 K for 12 d.

5. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2[link]. For each sample, a small amount of powder was ground and mounted on a low-background silicon wafer with a drop of acetone. These were mounted in flat-plate mode on a PANalytical X'Pert Pro MPD diffractometer. X-ray powder diffraction data were collected at 293 K using CuKα X-rays over the range 10–80°/2θ using a PANalytical X'Celerator area detector. The powder diffraction data collection time for each sample was 8 h 20 min.

Table 2
Experimental details

  Rb2NiSi5O12 Rb2MnSi5O12
Crystal data
Chemical formula Rb2NiSi5O12 Rb2MnSi5O12
Mr 562.06 557.92
Crystal system, space group Orthorhombic, Pbca Orthorhombic, Pbca
Temperature (K) 293 293
a, b, c (Å) 13.469 (3), 13.480 (3), 13.442 (2) 13.4085 (10), 13.6979 (11), 13.5761 (10)
V3) 2440.7 (8) 2493.5 (3)
Z 8 8
Radiation type Cu Kα, λ = 1.540560 Å Cu Kα, λ = 1.540560 Å
Specimen shape, size (mm) Irregular, 10 × 10 Irregular, 10 × 10
 
Data collection
Diffractometer PANalytical X'Pert Pro MPD PANalytical X'Pert Pro MPD
Specimen mounting Flat plate Flat plate
Data collection mode Reflection Reflection
Scan method Step Step
2θ values (°) 2θmin = 9.897 2θmax = 79.883 2θstep = 0.017 2θmin = 10.139 2θmax = 80.125 2θstep = 0.017
 
Refinement
R factors and goodness of fit Rp = 9.048, Rwp = 12.007, Rexp = 4.263, RBragg = 10.421, χ2 = 7.935 Rp = 6.527, Rwp = 8.847, Rexp = 3.909, RBragg = 5.989, χ2 = 5.121
No. of parameters 73 71
No. of restraints 24 24
Computer programs: X'Pert Data Collector (PANalytical, 2006[PANalytical (2006). X'Pert Data Collector. PANalytical, Almelo, The Netherlands.]), FULLPROF (Rodríguez-Carvajal, 1993[Rodríguez-Carvajal, J. (1993). Phys. B: Condens. Matter, 192, 55-69.]), VESTA (Momma & Izumi, 2008[Momma, K. & Izumi, F. (2008). J. Appl. Cryst. 41, 653-658.]) and publCIF (Westrip, 2010[Westrip, S. P. (2010). J. Appl. Cryst. 43, 920-925.]).

All Bragg reflections in both of the powder diffraction patterns could be indexed in the space group Pbca with similar lattice parameters to that for the Cs2CdSi5O12 leucite (Bell et al., 1994a[Bell, A. M. T., Henderson, C. M. B., Redfern, S. A. T., Cernik, R. J., Champness, P. E., Fitch, A. N. & Kohn, S. C. (1994a). Acta Cryst. B50, 31-41.]). The crystal structures (Bell & Henderson, 1996[Bell, A. M. T. & Henderson, C. M. B. (1996). Acta Cryst. C52, 2132-2139.]) of Cs2NiSi5O12 (X = Ni) and Cs2MnSi5O12 (X = Mn) were respectively used as starting models for Rietveld (1969[Rietveld, H. M. (1969). J. Appl. Cryst. 2, 65-71.]) refinements. In both cases, Rb+ replaced Cs+ as the extraframework cation. Isotropic atomic displacement parameters were used for all atoms in these phases. In both refinements, the isotropic atomic displacement parameters were constrained to be the same for all sites occupied by the same element, each Rb site had the same displacement parameter as did each Si site and each O site. Soft constraints were used for both refinements, in both cases the Si—O distances were constrained to be 1.61±0.02 Å. For X = Ni, the Ni—O distances were constrained to be 1.88±0.02 Å, the mean Ni—O distance for Cs2NiSi5O12. For X = Mn, the Mn—O distances were constrained to be 1.98±0.02 Å, the mean Mn—O distance for Cs2MnSi5O12. In both cases, Si and X atoms were ordered onto separate tetra­hedrally coordinated sites, both refined structures are similar.

Supporting information


Chemical context top

Synthetic analogues of the silicate framework minerals leucite KAlSi2O6 (Mazzi et al., 1976) and pollucite CsAlSi2O6 (Dimitrijevic et al., 1991) can be prepared with the general formulae AB2O6 and A2CSi5O12. A is an alkali metal cation (K, Rb, Cs), B is a trivalent cation (Al, B, Fe3+) and C is a divalent cation (Be, Mg, Mn, Fe2+, Co, Ni, Cu, Zn, Cd). The title compounds are leucite analogues with A = Rb and C = Ni and Mn, these structures are in the space group Pbca and are isostructural with Cs2CdSi5O12 (Bell et al., 1994b).

These leucite structures all have the same topology, a silicate framework structure with B or C cations partially substituting on the tetra­hedrally coordinated silicon sites (T-sites). A cations sit in the extraframework channels, these extraframework cations can be removed by ion exchange which makes them of technological inter­est as a possible storage medium for radioactive Cs from nuclear waste (Gatta et al., 2008.)

Structural commentary top

For the X = Ni refinement, the Ni site isotropic temperature factor was larger than expected [Biso = 7.5 (9) Å2]. Also the mean Ni–O bond length for the NiO4 tetra­hedron is 1.90 (2) Å, shorter than that seen in tetra­hedrally coordinated NiO4 units. NiCr2O4 has the cubic spinel structure with Ni in tetra­hedral coordination. A single-crystal structure refinement (Crottaz et al., 1997) gives the Ni—O distance as 1.967 (3) Å. An EXAFS/XANES study (Farges et al., 2001) gives the Ni—O distance as 1.96 (1) Å. The mean Si—O bond length for the SiO4 tetra­hedra in this structure is 1.643 (7)Å, which is slightly larger than the range of Si—O distances for silicates [1.59–1.63 Å; Inter­national Tables for X-ray Crystallography (1975, Vol. III, Table 4.1.1)]. These differences in the Ni—O and Si—O distances suggest some possible T-site cation disorder with some Si on the Ni site. A future higher quality neutron/synchrotron X-ray powder diffraction study may show if there really is Ni/Si T-site cation disorder.

Fig. 1 shows the Rietveld difference plot for Rb2NiSi5O12. The crystal structure of Rb2NiSi5O12 is displayed in Fig. 2 and consists of a framework of corner-sharing tetra­hedral SiO4 and NiO4 units, and Rb cations sitting in the extraframework channels.

For the X = Mn refinement, unlike in the X = Ni sample, the mean Mn—O distance is 2.02 (1) Å. This is in agreement with the mean Mn—O distance for Cs2MnSi5O12 (1.98 (3) Å; Bell & Henderson, 1996). This would suggest that this structure has complete T-site cation ordering. However, the isotropic temperature factors for the Mn site and the O sites could not be refined to chemically sensible positive values, so these were both fixed at Biso = 0.1 Å2. This refinement was done assuming that Mn was present as Mn2+ and that all sites were fully occupied. If some or all of the Mn atoms were present with a higher oxidation state, then this could account for the problem with refining these temperature factors. However, a higher quality neutron/synchrotron X-ray powder diffraction study may also be needed for a more precise determination of the state of Mn in this structure.

Fig. 3 shows the Rietveld difference plot for Rb2MnSi5O12 . The crystal structure of Rb2MnSi5O12 is displayed in Fig. 4 and consists of a framework of corner-sharing tetra­hedral SiO4 and MnO4 units; Rb cations sit in the extraframework channels. Note how inclusion of the larger Mn cation in the silicate framework compared to Ni causes the central channel of the crystal structure to be slightly more distorted for Rb2MnSi5O12 (Fig. 4) compared to Rb2NiSi5O12 (Fig. 2).

Database survey top

Many different leucite analogue crystal structures are known at ambient temperature. Table 1 gives stoichiometries, space groups, lattice parameters, and references for some known ambient temperature leucite crystal structures. In addition, a high-temperature structure for Cs2ZnSi5O12 in the space group Pa3 has been reported above 566 K (Bell & Henderson, 2012).

Synthesis and crystallization top

The samples were made from stoichiometric mixtures of Rb2CO3, SiO2 and NiO (X = Ni) or MnO (X = Mn). These mixtures were ground together and then heated overnight at 873 K to decompose the carbonates, then melted in platinum crucibles at 1573 K for 1.5 h (X = Ni) or 1673 K for 2 h (X = Mn) before quenching to form glasses. The glasses were dry-crystallized at ambient pressure and 1193 K for 12 d.

Refinement top

Crystal data, data collection and structure refinement details are summarized in Table 2. For each sample, a small amount of powder was ground and mounted a low-background silicon wafer with a drop of acetone. These were mounted in flat-plate mode on a PANalytical X'Pert Pro MPD diffractometer. X-ray powder diffraction data were collected at 293 K using CuKα X-rays over the range 10–80°2θ using a PANalytical X'Celerator area detector. The powder diffraction data collection times for each sample were 8 h 20 min.

All Bragg reflections in both of the powder diffraction patterns could be indexed in the space group Pbca with similar lattice parameters to that for the Cs2CdSi5O12 leucite (Bell et al., 1994a). The crystal structures (Bell & Henderson, 1996) of Cs2NiSi5O12 (X = Ni) and Cs2MnSi5O12 (X = Mn) were respectively used as starting models for Rietveld (1969) refinements. In both cases, Rb replaced Cs as the extraframework cation. Isotropic atomic displacement parameters were used for all atoms in these phases. In both refinements, the isotropic atomic displacement parameters were constrained to be the same for all sites occupied by the same element, each Rb site had the same displacement parameter as did each Si site and each O site. Soft constraints were used for both refinements, in both cases the Si—O distances were constrained to be 1.61±0.02 Å. For X = Ni, the Ni–O distances were constrained to be 1.88±0.02 Å, the mean Ni—O distance for Cs2NiSi5O12. For X = Mn, the Mn—O distances were constrained to be 1.98±0.02 Å, the mean Mn—O distance for Cs2MnSi5O12. In both cases, Si and X atoms were ordered onto separate tetra­hedrally coordinated sites, both refined structures are similar.

Related literature top

For the crystal chemistry of leucite analogues, see: Agakhanov et al. (2012); Dimitrijevic et al. (1991); Bell & Henderson (1994a, 1994b, 1996, 2009, 2012); Bell et al. (1994a, 1994b, 2010); Bubnova et al. (2004); Mazzi et al. (1976); Torres-Martinez & West (1986); Torres-Martinez et al. (1984);

Atomic coordinates as starting parameters for the Rietveld refinement (Rietveld, 1969) of the present phases were taken from Bell & Henderson (2009).

Structure description top

Synthetic analogues of the silicate framework minerals leucite KAlSi2O6 (Mazzi et al., 1976) and pollucite CsAlSi2O6 (Dimitrijevic et al., 1991) can be prepared with the general formulae AB2O6 and A2CSi5O12. A is an alkali metal cation (K, Rb, Cs), B is a trivalent cation (Al, B, Fe3+) and C is a divalent cation (Be, Mg, Mn, Fe2+, Co, Ni, Cu, Zn, Cd). The title compounds are leucite analogues with A = Rb and C = Ni and Mn, these structures are in the space group Pbca and are isostructural with Cs2CdSi5O12 (Bell et al., 1994b).

These leucite structures all have the same topology, a silicate framework structure with B or C cations partially substituting on the tetra­hedrally coordinated silicon sites (T-sites). A cations sit in the extraframework channels, these extraframework cations can be removed by ion exchange which makes them of technological inter­est as a possible storage medium for radioactive Cs from nuclear waste (Gatta et al., 2008.)

For the X = Ni refinement, the Ni site isotropic temperature factor was larger than expected [Biso = 7.5 (9) Å2]. Also the mean Ni–O bond length for the NiO4 tetra­hedron is 1.90 (2) Å, shorter than that seen in tetra­hedrally coordinated NiO4 units. NiCr2O4 has the cubic spinel structure with Ni in tetra­hedral coordination. A single-crystal structure refinement (Crottaz et al., 1997) gives the Ni—O distance as 1.967 (3) Å. An EXAFS/XANES study (Farges et al., 2001) gives the Ni—O distance as 1.96 (1) Å. The mean Si—O bond length for the SiO4 tetra­hedra in this structure is 1.643 (7)Å, which is slightly larger than the range of Si—O distances for silicates [1.59–1.63 Å; Inter­national Tables for X-ray Crystallography (1975, Vol. III, Table 4.1.1)]. These differences in the Ni—O and Si—O distances suggest some possible T-site cation disorder with some Si on the Ni site. A future higher quality neutron/synchrotron X-ray powder diffraction study may show if there really is Ni/Si T-site cation disorder.

Fig. 1 shows the Rietveld difference plot for Rb2NiSi5O12. The crystal structure of Rb2NiSi5O12 is displayed in Fig. 2 and consists of a framework of corner-sharing tetra­hedral SiO4 and NiO4 units, and Rb cations sitting in the extraframework channels.

For the X = Mn refinement, unlike in the X = Ni sample, the mean Mn—O distance is 2.02 (1) Å. This is in agreement with the mean Mn—O distance for Cs2MnSi5O12 (1.98 (3) Å; Bell & Henderson, 1996). This would suggest that this structure has complete T-site cation ordering. However, the isotropic temperature factors for the Mn site and the O sites could not be refined to chemically sensible positive values, so these were both fixed at Biso = 0.1 Å2. This refinement was done assuming that Mn was present as Mn2+ and that all sites were fully occupied. If some or all of the Mn atoms were present with a higher oxidation state, then this could account for the problem with refining these temperature factors. However, a higher quality neutron/synchrotron X-ray powder diffraction study may also be needed for a more precise determination of the state of Mn in this structure.

Fig. 3 shows the Rietveld difference plot for Rb2MnSi5O12 . The crystal structure of Rb2MnSi5O12 is displayed in Fig. 4 and consists of a framework of corner-sharing tetra­hedral SiO4 and MnO4 units; Rb cations sit in the extraframework channels. Note how inclusion of the larger Mn cation in the silicate framework compared to Ni causes the central channel of the crystal structure to be slightly more distorted for Rb2MnSi5O12 (Fig. 4) compared to Rb2NiSi5O12 (Fig. 2).

Many different leucite analogue crystal structures are known at ambient temperature. Table 1 gives stoichiometries, space groups, lattice parameters, and references for some known ambient temperature leucite crystal structures. In addition, a high-temperature structure for Cs2ZnSi5O12 in the space group Pa3 has been reported above 566 K (Bell & Henderson, 2012).

For the crystal chemistry of leucite analogues, see: Agakhanov et al. (2012); Dimitrijevic et al. (1991); Bell & Henderson (1994a, 1994b, 1996, 2009, 2012); Bell et al. (1994a, 1994b, 2010); Bubnova et al. (2004); Mazzi et al. (1976); Torres-Martinez & West (1986); Torres-Martinez et al. (1984);

Atomic coordinates as starting parameters for the Rietveld refinement (Rietveld, 1969) of the present phases were taken from Bell & Henderson (2009).

Synthesis and crystallization top

The samples were made from stoichiometric mixtures of Rb2CO3, SiO2 and NiO (X = Ni) or MnO (X = Mn). These mixtures were ground together and then heated overnight at 873 K to decompose the carbonates, then melted in platinum crucibles at 1573 K for 1.5 h (X = Ni) or 1673 K for 2 h (X = Mn) before quenching to form glasses. The glasses were dry-crystallized at ambient pressure and 1193 K for 12 d.

Refinement details top

Crystal data, data collection and structure refinement details are summarized in Table 2. For each sample, a small amount of powder was ground and mounted a low-background silicon wafer with a drop of acetone. These were mounted in flat-plate mode on a PANalytical X'Pert Pro MPD diffractometer. X-ray powder diffraction data were collected at 293 K using CuKα X-rays over the range 10–80°2θ using a PANalytical X'Celerator area detector. The powder diffraction data collection times for each sample were 8 h 20 min.

All Bragg reflections in both of the powder diffraction patterns could be indexed in the space group Pbca with similar lattice parameters to that for the Cs2CdSi5O12 leucite (Bell et al., 1994a). The crystal structures (Bell & Henderson, 1996) of Cs2NiSi5O12 (X = Ni) and Cs2MnSi5O12 (X = Mn) were respectively used as starting models for Rietveld (1969) refinements. In both cases, Rb replaced Cs as the extraframework cation. Isotropic atomic displacement parameters were used for all atoms in these phases. In both refinements, the isotropic atomic displacement parameters were constrained to be the same for all sites occupied by the same element, each Rb site had the same displacement parameter as did each Si site and each O site. Soft constraints were used for both refinements, in both cases the Si—O distances were constrained to be 1.61±0.02 Å. For X = Ni, the Ni–O distances were constrained to be 1.88±0.02 Å, the mean Ni—O distance for Cs2NiSi5O12. For X = Mn, the Mn—O distances were constrained to be 1.98±0.02 Å, the mean Mn—O distance for Cs2MnSi5O12. In both cases, Si and X atoms were ordered onto separate tetra­hedrally coordinated sites, both refined structures are similar.

Computing details top

For both compounds, data collection: X'Pert Data Collector (PANalytical, 2006). Program(s) used to refine structure: FULLPROF (Rodríguez-Carvajal, 1993) for Rb2NiSi5O12; FULLPROF (Rodríguez-Carvajal, 2001) for Rb2MnSi5O12. For both compounds, molecular graphics: VESTA (Momma & Izumi, 2008); software used to prepare material for publication: publCIF (Westrip, 2010).

Figures top
[Figure 1] Fig. 1. Rietveld difference plot for the single-phase refinement of Rb2NiSi5O12. The red, blue and green lines show, respectively, the observed, calculated and difference plots. Calculated Bragg reflection positions are indicated by crosses.
[Figure 2] Fig. 2. The crystal structure of Rb2NiSi5O12. Green spheres show Rb cations, blue polyhedra show SiO4 units, pink polyhedra show show NiO4 units and red spheres represent O atoms.
[Figure 3] Fig. 3. Rietveld difference plot for the single-phase refinement of Rb2MnSi5O12. The red, blue and green lines show, respectively, the observed, calculated and difference plots. Calculated Bragg reflection positions are indicated by crosses.
[Figure 4] Fig. 4. The crystal structure of Rb2MnSi5O12. Green spheres show Rb cations, blue polyhedra show SiO4 units, purple polyhedra show show MnO4 units and red spheres represent O atoms.
(Rb2NiSi5O12) Dirubidium nickel(II) pentasilicate top
Crystal data top
Rb2NiSi5O12Z = 8
Mr = 562.06Dx = 3.059 (1) Mg m3
Orthorhombic, PbcaCu Kα radiation, λ = 1.540560 Å
Hall symbol: -P 2ac 2abT = 293 K
a = 13.469 (3) Åpurple-blue
b = 13.480 (3) Åirregular, 10 × 10 mm
c = 13.442 (2) ÅSpecimen preparation: Prepared at 1193 K and 100 kPa
V = 2440.7 (8) Å3
Data collection top
PANalytical X'Pert Pro MPD
diffractometer
Data collection mode: reflection
Radiation source: X-ray tubeScan method: step
Specimen mounting: flat plate2θmin = 9.897°, 2θmax = 79.883°, 2θstep = 0.017°
Refinement top
Rp = 9.0484189 data points
Rwp = 12.007Profile function: T-C-H Pseudo-Voigt
Rexp = 4.26373 parameters
RBragg = 10.42124 restraints
χ2 = 7.935Background function: cubic splines interpolation
Crystal data top
Rb2NiSi5O12V = 2440.7 (8) Å3
Mr = 562.06Z = 8
Orthorhombic, PbcaCu Kα radiation, λ = 1.540560 Å
a = 13.469 (3) ÅT = 293 K
b = 13.480 (3) Åirregular, 10 × 10 mm
c = 13.442 (2) Å
Data collection top
PANalytical X'Pert Pro MPD
diffractometer
Scan method: step
Specimen mounting: flat plate2θmin = 9.897°, 2θmax = 79.883°, 2θstep = 0.017°
Data collection mode: reflection
Refinement top
Rp = 9.048χ2 = 7.935
Rwp = 12.0074189 data points
Rexp = 4.26373 parameters
RBragg = 10.42124 restraints
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
Rb10.1367 (17)0.1209 (19)0.134 (2)0.128 (4)*
Rb20.4100 (17)0.3755 (18)0.4037 (19)0.128 (4)*
Ni10.3641 (11)0.8370 (10)0.9075 (10)0.095 (12)*
Si20.1383 (12)0.6631 (11)0.6170 (13)0.082 (6)*
Si30.5913 (12)0.1289 (16)0.6577 (12)0.082 (6)*
Si40.6419 (14)0.5703 (13)0.1057 (11)0.082 (6)*
Si50.9207 (11)0.3702 (12)0.8320 (14)0.082 (6)*
Si60.8342 (11)0.9051 (13)0.3647 (13)0.082 (6)*
O10.4680 (13)0.383 (4)0.155 (5)0.017 (3)*
O20.143 (5)0.4529 (14)0.415 (3)0.017 (3)*
O30.378 (5)0.130 (5)0.499 (2)0.017 (3)*
O40.7369 (14)0.436 (3)0.618 (6)0.017 (3)*
O50.658 (2)0.7205 (19)0.353 (6)0.017 (3)*
O60.416 (3)0.628 (6)0.7182 (13)0.017 (3)*
O70.9625 (14)0.861 (6)0.691 (2)0.017 (3)*
O80.633 (5)0.977 (2)0.860 (6)0.017 (3)*
O90.903 (2)0.633 (6)0.961 (2)0.017 (3)*
O100.2157 (13)0.928 (2)0.146 (5)0.017 (3)*
O110.169 (3)0.2028 (17)0.898 (5)0.017 (3)*
O120.881 (5)0.096 (5)0.223 (2)0.017 (3)*
Geometric parameters (Å, º) top
Rb1—O1i3.51 (6)Rb2—O11ii3.41 (5)
Rb1—O2ii3.11 (5)Rb2—O12iv4.15 (7)
Rb1—O3iii3.84 (7)Ni1—O4xvii1.93 (4)
Rb1—O3iv3.92 (7)Ni1—O7xvi1.90 (3)
Rb1—O4v3.68 (8)Ni1—O9xviii1.89 (3)
Rb1—O5vi3.08 (4)Ni1—O11xix1.87 (3)
Rb1—O6vii3.64 (8)Si2—O1xx1.64 (4)
Rb1—O7viii2.72 (4)Si2—O3xix1.66 (4)
Rb1—O8viii3.37 (7)Si2—O5xii1.64 (4)
Rb1—O9viii3.59 (8)Si2—O10xxi1.66 (3)
Rb1—O10ix2.81 (4)Si3—O1xxii1.67 (2)
Rb1—O11x3.39 (7)Si3—O2xxiii1.63 (4)
Rb1—O12xi3.65 (7)Si3—O6xiii1.67 (2)
Rb1—O12iv3.84 (6)Si3—O11xxiv1.63 (5)
Rb2—O13.43 (7)Si4—O2xxv1.61 (3)
Rb2—O23.75 (7)Si4—O3xxvi1.64 (4)
Rb2—O33.58 (7)Si4—O4xv1.64 (3)
Rb2—O4viii3.23 (4)Si4—O12xxvii1.65 (4)
Rb2—O5vi4.14 (7)Si5—O5xxviii1.64 (3)
Rb2—O5viii3.64 (8)Si5—O7xxix1.61 (3)
Rb2—O6viii2.85 (4)Si5—O8xxx1.65 (4)
Rb2—O7xii3.84 (8)Si5—O12xxii1.62 (4)
Rb2—O8xiii3.51 (8)Si6—O6xxxi1.64 (4)
Rb2—O8xiv3.65 (6)Si6—O8xxxii1.65 (4)
Rb2—O9xv2.63 (4)Si6—O9xiv1.67 (4)
Rb2—O9xvi3.92 (8)Si6—O10xxv1.63 (2)
Rb2—O10i3.92 (7)
O4xvii—Ni1—O7xvi104 (3)O5xxviii—Si5—O7xxix127 (3)
O4xvii—Ni1—O9xviii102 (4)O5xxviii—Si5—O8xxx109 (3)
O4xvii—Ni1—O11xix119 (3)O5xxviii—Si5—O12xxii99 (5)
O7xvi—Ni1—O9xviii115 (2)O7xxix—Si5—O8xxx123 (5)
O7xvi—Ni1—O11xix106 (4)O7xxix—Si5—O12xxii99 (4)
O9xviii—Ni1—O11xix110 (4)O8xxx—Si5—O12xxii80 (4)
O1xx—Si2—O3xix95 (4)O6xxxi—Si6—O8xxxii93 (5)
O1xx—Si2—O5xii115 (4)O6xxxi—Si6—O9xiv94 (3)
O1xx—Si2—O10xxi101 (2)O6xxxi—Si6—O10xxv131 (4)
O3xix—Si2—O5xii121 (5)O8xxxii—Si6—O9xiv100 (5)
O3xix—Si2—O10xxi96 (4)O8xxxii—Si6—O10xxv94 (4)
O5xii—Si2—O10xxi123 (3)O9xiv—Si6—O10xxv132 (4)
O1xxii—Si3—O2xxiii110 (4)Si2vii—O1—Si3ii147 (2)
O1xxii—Si3—O6xiii87 (3)Si3v—O2—Si4iv124 (2)
O1xxii—Si3—O11xxiv134 (4)Si2i—O3—Si4vi158 (3)
O2xxiii—Si3—O6xiii128 (4)Ni1xiii—O4—Si4xxviii130 (2)
O2xxiii—Si3—O11xxiv82 (3)Si2xxxi—O5—Si5xv131 (2)
O6xiii—Si3—O11xxiv120 (5)Si3xvii—O6—Si6xii129 (2)
O2xxv—Si4—O3xxvi110 (4)Ni1xxiv—O7—Si5xxxiii124.2 (18)
O2xxv—Si4—O4xv88 (3)Si5xxvii—O8—Si6xxxiv165 (3)
O2xxv—Si4—O12xxvii112 (4)Ni1xxxv—O9—Si6xxi129 (2)
O3xxvi—Si4—O4xv106 (5)Si2xiv—O10—Si6iv117.0 (19)
O3xxvi—Si4—O12xxvii133 (3)Ni1i—O11—Si3xvi118 (2)
O4xv—Si4—O12xxvii96 (4)Si4xxx—O12—Si5ii171 (3)
Symmetry codes: (i) x+1/2, y1/2, z; (ii) x, y+1/2, z1/2; (iii) x+1/2, y, z1/2; (iv) x1/2, y, z+1/2; (v) x1/2, y+1/2, z+1; (vi) x+1, y1/2, z+1/2; (vii) x+1/2, y+1, z1/2; (viii) x+1, y+1, z+1; (ix) x, y1, z; (x) x, y, z1; (xi) x1, y, z; (xii) x1/2, y+3/2, z+1; (xiii) x+1, y1/2, z+3/2; (xiv) x, y+3/2, z1/2; (xv) x+3/2, y+1, z1/2; (xvi) x1/2, y, z+3/2; (xvii) x+1, y+1/2, z+3/2; (xviii) x1/2, y+3/2, z+2; (xix) x+1/2, y+1/2, z; (xx) x+1/2, y+1, z+1/2; (xxi) x, y+3/2, z+1/2; (xxii) x, y+1/2, z+1/2; (xxiii) x+1/2, y+1/2, z+1; (xxiv) x+1/2, y, z+3/2; (xxv) x+1/2, y, z+1/2; (xxvi) x+1, y+1/2, z+1/2; (xxvii) x+3/2, y+1/2, z; (xxviii) x+3/2, y+1, z+1/2; (xxix) x+2, y1/2, z+3/2; (xxx) x+3/2, y1/2, z; (xxxi) x+1/2, y+3/2, z+1; (xxxii) x+3/2, y+2, z1/2; (xxxiii) x+2, y+1/2, z+3/2; (xxxiv) x+3/2, y+2, z+1/2; (xxxv) x+1/2, y+3/2, z+2.
(Rb2MnSi5O12) Dirubidium managnese(II) pentasilicate top
Crystal data top
Rb2MnSi5O12Z = 8
Mr = 557.92Dx = 2.975 (1) Mg m3
Orthorhombic, PbcaCu Kα radiation, λ = 1.540560 Å
Hall symbol: -P 2ac 2abT = 293 K
a = 13.4085 (10) Åpale brown-pink
b = 13.6979 (11) Åirregular, 10 × 10 mm
c = 13.5761 (10) ÅSpecimen preparation: Prepared at 1193 K and 100 kPa
V = 2493.5 (3) Å3
Data collection top
PANalytical X'Pert Pro MPD
diffractometer
Data collection mode: reflection
Radiation source: X-ray tubeScan method: step
Specimen mounting: flat plate2θmin = 10.139°, 2θmax = 80.125°, 2θstep = 0.017°
Refinement top
Rp = 6.5274189 data points
Rwp = 8.847Profile function: T-C-H Pseudo-Voigt
Rexp = 3.90971 parameters
RBragg = 5.98924 restraints
χ2 = 5.121Background function: cubic splines interpolation
Crystal data top
Rb2MnSi5O12V = 2493.5 (3) Å3
Mr = 557.92Z = 8
Orthorhombic, PbcaCu Kα radiation, λ = 1.540560 Å
a = 13.4085 (10) ÅT = 293 K
b = 13.6979 (11) Åirregular, 10 × 10 mm
c = 13.5761 (10) Å
Data collection top
PANalytical X'Pert Pro MPD
diffractometer
Scan method: step
Specimen mounting: flat plate2θmin = 10.139°, 2θmax = 80.125°, 2θstep = 0.017°
Data collection mode: reflection
Refinement top
Rp = 6.527χ2 = 5.121
Rwp = 8.8474189 data points
Rexp = 3.90971 parameters
RBragg = 5.98924 restraints
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
Rb10.1311 (8)0.1348 (8)0.1535 (6)0.0544 (19)*
Rb20.3811 (10)0.3968 (7)0.3953 (7)0.0544 (19)*
Mn10.3707 (9)0.8342 (7)0.9432 (6)0.00127*
Si20.1328 (11)0.6601 (10)0.6011 (10)0.024 (2)*
Si30.5921 (11)0.1146 (10)0.6255 (10)0.024 (2)*
Si40.6449 (10)0.5993 (11)0.1054 (10)0.024 (2)*
Si50.9006 (10)0.3583 (11)0.8208 (10)0.024 (2)*
Si60.8312 (11)0.9317 (10)0.3329 (11)0.024 (2)*
O10.4758 (12)0.355 (3)0.1607 (19)0.00127*
O20.083 (2)0.4973 (12)0.399 (3)0.00127*
O30.397 (2)0.150 (3)0.4890 (13)0.00127*
O40.7328 (12)0.4230 (19)0.620 (2)0.00127*
O50.659 (2)0.7326 (14)0.360 (2)0.00127*
O60.363 (4)0.632 (2)0.7605 (17)0.00127*
O70.9822 (15)0.877 (3)0.645 (2)0.00127*
O80.659 (3)0.9530 (13)0.860 (3)0.00127*
O90.893 (2)0.635 (2)0.9119 (13)0.00127*
O100.2099 (14)0.9281 (18)0.135 (3)0.00127*
O110.132 (3)0.1885 (12)0.9545 (17)0.00127*
O120.892 (3)0.139 (3)0.2068 (12)0.00127*
Geometric parameters (Å, º) top
Rb1—O1i4.09 (4)Rb2—O10i3.76 (4)
Rb1—O2ii3.51 (3)Rb2—O11iii3.63 (4)
Rb1—O2iii3.95 (4)Rb2—O12iv3.80 (4)
Rb1—O3iv3.69 (3)Mn1—O4xvii2.04 (2)
Rb1—O4v3.46 (3)Mn1—O7xvi2.00 (3)
Rb1—O5vi3.12 (3)Mn1—O9xviii2.03 (2)
Rb1—O6vii3.51 (3)Mn1—O11xix2.002 (19)
Rb1—O7viii3.13 (3)Si2—O1xx1.68 (2)
Rb1—O8viii3.07 (4)Si2—O3xix1.58 (2)
Rb1—O9viii3.29 (3)Si2—O5xii1.60 (2)
Rb1—O10ix3.03 (3)Si2—O10xxi1.66 (3)
Rb1—O11x2.80 (2)Si3—O1xxii1.68 (2)
Rb1—O12xi3.29 (4)Si3—O2xxiii1.57 (2)
Rb1—O12iv3.98 (4)Si3—O6xiv1.68 (3)
Rb2—O13.48 (3)Si3—O11xxiv1.58 (3)
Rb2—O24.23 (3)Si4—O2xxv1.63 (2)
Rb2—O33.62 (4)Si4—O3xxvi1.56 (3)
Rb2—O4viii2.91 (3)Si4—O4xv1.68 (2)
Rb2—O5vi4.17 (3)Si4—O12xxvii1.56 (3)
Rb2—O5viii3.80 (3)Si5—O5xxviii1.57 (3)
Rb2—O6vii3.77 (5)Si5—O7xxix1.66 (3)
Rb2—O6viii4.05 (5)Si5—O8xiii1.61 (3)
Rb2—O7xii3.43 (4)Si5—O12xxii1.55 (2)
Rb2—O7xiii3.86 (3)Si6—O6xxx1.60 (3)
Rb2—O8xiv3.45 (4)Si6—O8xxxi1.63 (2)
Rb2—O9xv3.07 (3)Si6—O9xxxii1.63 (3)
Rb2—O9xvi4.19 (3)Si6—O10xxv1.68 (3)
O4xvii—Mn1—O7xvi94.7 (15)O5xxviii—Si5—O7xxix121 (3)
O4xvii—Mn1—O9xviii112.6 (18)O5xxviii—Si5—O8xiii106 (2)
O4xvii—Mn1—O11xix128.0 (19)O5xxviii—Si5—O12xxii109 (3)
O7xvi—Mn1—O9xviii114.1 (18)O7xxix—Si5—O8xiii105 (3)
O7xvi—Mn1—O11xix111 (2)O7xxix—Si5—O12xxii110 (3)
O9xviii—Mn1—O11xix97.8 (16)O8xiii—Si5—O12xxii106 (3)
O1xx—Si2—O3xix104 (2)O6xxx—Si6—O8xxxi134 (3)
O1xx—Si2—O5xii98 (2)O6xxx—Si6—O9xxxii94 (2)
O1xx—Si2—O10xxi109 (2)O6xxx—Si6—O10xxv117 (3)
O3xix—Si2—O5xii117 (3)O8xxxi—Si6—O9xxxii111 (2)
O3xix—Si2—O10xxi111 (3)O8xxxi—Si6—O10xxv93 (2)
O5xii—Si2—O10xxi116 (2)O9xxxii—Si6—O10xxv108 (2)
O1xxii—Si3—O2xxiii103 (3)Si2vii—O1—Si3iii134.2 (18)
O1xxii—Si3—O6xiv92 (3)Si3v—O2—Si4iv142.2 (18)
O1xxii—Si3—O11xxiv111 (3)Si2i—O3—Si4vi137.6 (19)
O2xxiii—Si3—O6xiv111 (3)Mn1xiv—O4—Si4xxviii120.5 (14)
O2xxiii—Si3—O11xxiv120 (2)Si2xxx—O5—Si5xv136.4 (19)
O6xiv—Si3—O11xxiv115 (2)Si3xvii—O6—Si6xii138 (2)
O2xxv—Si4—O3xxvi100 (3)Mn1xxiv—O7—Si5xxxiii146.0 (16)
O2xxv—Si4—O4xv110 (2)Si5xxvii—O8—Si6xxxiv138.2 (19)
O2xxv—Si4—O12xxvii100 (3)Mn1xxxv—O9—Si6xxi132.5 (15)
O3xxvi—Si4—O4xv122 (2)Si2xxxii—O10—Si6iv134.1 (18)
O3xxvi—Si4—O12xxvii117 (2)Mn1i—O11—Si3xvi125.5 (15)
O4xv—Si4—O12xxvii106 (3)Si4xiii—O12—Si5iii155.7 (19)
Symmetry codes: (i) x+1/2, y1/2, z; (ii) x, y1/2, z+1/2; (iii) x, y+1/2, z1/2; (iv) x1/2, y, z+1/2; (v) x1/2, y+1/2, z+1; (vi) x+1, y1/2, z+1/2; (vii) x+1/2, y+1, z1/2; (viii) x+1, y+1, z+1; (ix) x, y1, z; (x) x, y, z1; (xi) x1, y, z; (xii) x1/2, y+3/2, z+1; (xiii) x+3/2, y1/2, z; (xiv) x+1, y1/2, z+3/2; (xv) x+3/2, y+1, z1/2; (xvi) x1/2, y, z+3/2; (xvii) x+1, y+1/2, z+3/2; (xviii) x1/2, y+3/2, z+2; (xix) x+1/2, y+1/2, z; (xx) x+1/2, y+1, z+1/2; (xxi) x, y+3/2, z+1/2; (xxii) x, y+1/2, z+1/2; (xxiii) x+1/2, y+1/2, z+1; (xxiv) x+1/2, y, z+3/2; (xxv) x+1/2, y, z+1/2; (xxvi) x+1, y+1/2, z+1/2; (xxvii) x+3/2, y+1/2, z; (xxviii) x+3/2, y+1, z+1/2; (xxix) x+2, y1/2, z+3/2; (xxx) x+1/2, y+3/2, z+1; (xxxi) x+3/2, y+2, z1/2; (xxxii) x, y+3/2, z1/2; (xxxiii) x+2, y+1/2, z+3/2; (xxxiv) x+3/2, y+2, z+1/2; (xxxv) x+1/2, y+3/2, z+2.
Crystal structure parameters (Å°) for room-temperature leucite analogues top
StoichiometrySGabcβV
K2MgSi5O12aIa3d13.4190 (1)13.4190 (1)13.4190 (1)902416.33 (5)
K2MgSi5O12aP21/c13.168 (5)13.652 (1)13.072 (5)91.69 (5)2348 (2)
Cs2CdSi5O12bPbca13.6714 (1)13.8240 (1)13.8939 (1)902625.83 (6)
Cs2CuSi5O12cPbca13.58943 (6)13.57355 (5)13.62296 (4)902512.847 (13)
Cs2CuSi5O12cIa3d13.6322 (4)13.6322 (4)13.6322 (4)902533.4 (2)
Cs2MgSi5O12dPbca13.6371 (5)13.6689 (5)13.7280 (5)902559.0 (2)
Rb2MgSi5O12dPbca13.422 (1)13.406 (1)13.730 (1)902470.6 (4)
Cs2ZnSi5O12dPbca13.6415 (9)13.6233 (8)13.6653 (9)902539.6 (3)
Rb2CdSi5O12ePbca13.4121 (1)13.6816 (1)13.8558 (1)902542.51 (5)
Cs2MnSi5O12ePbca13.6878 (3)13.7931 (3)13.7575 (3)902597.4 (2)
Cs2CoSi5O12ePbca13.6487 (4)13.7120 (4)13.6828 (4)902560.7 (2)
Cs2NiSi5O12ePbca13.6147 (3)13.6568 (5)13.6583 (5)902539.5 (1)
Rb2ZnSi5O12fIa3d13.4972 (1)13.4972 (1)13.4972 (1)902458.86 (3)
KFeSi2O6gI41/a13.2207 (3)13.2207 (3)13.9464 (3)902437.6 (2)
RbFeSi2O6gI41/a13.4586 (1)13.4586 (1)13.9380 (1)902524.63 (5)
CsFeSi2O6gIa3d13.8542 (1)13.8542 (1)13.8542 (1)902653.98 (3)
CsBSi2O6hI41/a13.019 (2)13.019 (2)12.899 (3)902186 (1)
CsAlSi2O6iIa3d13.647 (3)13.647 (3)13.647 (3)902541.6 (6)
KAlSi2O6jI41/a13.09 (1)13.09 (1)13.75 (1)902356 (5)
Cs0.814B1.092Si1.977O6kIa-3d13.009 (8)13.009 (8)13.009 (8)902202 (1)
Rb2MgSi5O12lIa3d13.530 (1)13.530 (1)13.530 (1)902476.8 (2)
Cs2BeSi5O12mIa3d13.406 (1)13.406 (1)13.406 (1)902409.3 (2)
Notes: SG = space group; all α and γ angles = 90°; (a) Bell et al. (1994a\bbr00); (b) Bell et al. (1994b); (c) Bell et al. (2010); (d) Bell & Henderson (2009); (e) Bell & Henderson (1996); (f) Bell & Henderson (1994a); (g) Bell & Henderson (1994b); (h) Agakhanov et al. (2012); (i) Dimitrijevic et al. (1991); (j) Mazzi et al. (1976); (k) Bubnova et al. (2004); (l) Torres-Martinez & West (1986); (m) Torres-Martinez et al. (1984).

Experimental details

(Rb2NiSi5O12)(Rb2MnSi5O12)
Crystal data
Chemical formulaRb2NiSi5O12Rb2MnSi5O12
Mr562.06557.92
Crystal system, space groupOrthorhombic, PbcaOrthorhombic, Pbca
Temperature (K)293293
a, b, c (Å)13.469 (3), 13.480 (3), 13.442 (2)13.4085 (10), 13.6979 (11), 13.5761 (10)
V3)2440.7 (8)2493.5 (3)
Z88
Radiation typeCu Kα, λ = 1.540560 ÅCu Kα, λ = 1.540560 Å
Specimen shape, size (mm)Irregular, 10 × 10Irregular, 10 × 10
Data collection
DiffractometerPANalytical X'Pert Pro MPD
diffractometer
PANalytical X'Pert Pro MPD
diffractometer
Specimen mountingFlat plateFlat plate
Data collection modeReflectionReflection
Scan methodStepStep
2θ values (°)2θmin = 9.897 2θmax = 79.883 2θstep = 0.0172θmin = 10.139 2θmax = 80.125 2θstep = 0.017
Refinement
R factors and goodness of fitRp = 9.048, Rwp = 12.007, Rexp = 4.263, RBragg = 10.421, χ2 = 7.935Rp = 6.527, Rwp = 8.847, Rexp = 3.909, RBragg = 5.989, χ2 = 5.121
No. of parameters7371
No. of restraints2424

Computer programs: X'Pert Data Collector (PANalytical, 2006), FULLPROF (Rodríguez-Carvajal, 1993), FULLPROF (Rodríguez-Carvajal, 2001), VESTA (Momma & Izumi, 2008), publCIF (Westrip, 2010).

 

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Volume 72| Part 2| February 2016| Pages 249-252
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