research communications
2.49Nd7.51(SiO4)6O1.75
of apatite type CaaKU Leuven - University of Leuven, Department of Metallurgy and Materials Engineering, Kasteelpark Arenberg 44 - bus 2450, B-3001 Heverlee, Belgium, and bKU Leuven - University of Leuven, Department of Chemistry, Celestijnenlaan 200F - bus 2404, B-3001 Heverlee, Belgium
*Correspondence e-mail: luc.vanmeervelt@chem.kuleuven.be
The title compound, Ca2+xNd8–x(SiO4)6O2–0.5x (x = 0.49), was synthesized at 1873 K and rapidly quenched to room temperature. Its structure has been determined using single-crystal X-ray diffraction and compared with results reported using neutron and X-ray powder diffraction from samples prepared by slow cooling. The single-crystal structure from room temperature data was found to belong to the P63/m and has the composition Ca2.49Nd7.51(SiO4)6O1.75 [dicalcium octaneodymium hexakis(orthosilicate) dioxide], being isotypic with natural apatite and the previously reported Ca2Nd8(SiO4)6O2 and Ca2.2Nd7.8(SiO4)6O1.9. The solubility limit of calcium in the equilibrium state at 1873 K was found to occur at a composition of Ca2+xNd8–x(SiO4)6O2–0.5x, where x = 0.49.
CCDC reference: 1447637
1. Chemical context
The study of calcium rare earth oxide silicates is important because they are usually observed in nuclear waste along with rare earth silicates. So far, the calcium rare earth oxide silicates of Nd (Fahey & Weber, 1982; Fahey et al., 1985), Sm (PDF 29–365; Smith, 1977), Eu (PDF 29–320; Smith, 1977), Gd (PDF 28–212; Smith, 1976), Tb (PDF 38–256; Lacout, 1986), and Ce (Skakle et al., 2000) have been studied. Fahey & Weber et al. (1982) and Fahey et al. (1985) published the structure and stoichiometry limits of the Ca2+xNd8–x(SiO4)2–0.5x system using X-ray and neutron powder diffraction. In that study, the samples were synthesized at 1523 or 1873 K and cooled at a rate of 250 K per hour. However, such a slow cooling process may lead to undesired modifications of the obtained specimens since the solubility of calcium does not remain constant but decreases with decreasing temperature. This problem is avoided in the present work by rapid quenching of the Ca2+xNd8–x(SiO4)6O2–0.5x samples in their equilibrium state at 1873 K to room temperature within a few seconds. Consequently, compositions of the samples can be preserved better.
2. Structural commentary
The single P63/m and has the composition Ca2.49Nd7.51(SiO4)6O1.75 and is isotypic with natural apatite and the previously reported Ca2Nd8(SiO4)6O2 and Ca2.2Nd7.8(SiO4)6O1.9 (Fahey & Weber, 1982; Fahey et al., 1985). The solubility limit of calcium in the equilibrium state at 1873 K was found to occur at a composition of Ca2+xNd8–x(SiO4)6O2–0.5x, where x = 0.49.
determined from room temperature data was found to belong to theThere are two metal positions in the ) and both contain disordered Nd and Ca ions: Nd1/Ca1 occupies the lower symmetry site 6h and Nd2/Ca2 the higher symmetry site 4f. The occupancies of these metal sites were refined resulting in 0.887 (5)/0.113 (5) for Nd1/Ca1 and 0.546 (4)/0.454 (4) for Nd2/Ca2. The majority (80%) of calcium is situated at the 4f site. In the structures of Ca2Nd8(SiO4)6O2 and Ca2.2Nd7.8(SiO4)6O1.9, these values are 89 and 73%, respectively (Fahey et al., 1985). The refined value of the amount of Nd in the structure gives a value of 0.49 for x in the equation Ca2+xNd8–x(SiO4)6O2–0.5x. For charge-balance purposes, the occupancy of O2− in the structure must be 2 − 0.5x or 1.755. Initially, the occupancy of the O2− position O4 in the structure was allowed to refine freely and its value was close to what is required for charge balance; however, it was fixed at 0.146 as the of heavy-atom positions is the most reliable and exact charge balance is required.
of the structure (Fig. 1The Nd1/Ca1 site is seven coordinate and the Nd/Ca—O bond lengths vary between 2.3909 (19) and 2.721 (3) Å for oxygen atoms of the SiO42− unit but the shortest bond length of 2.2681 (2) Å is to the O2− ion, O4 (Fig. 1; Table 1). The Nd2/Ca2 site is nine coordinate and only bonds to SiO42− units with six short distances [Nd—O = 2.4231 (17), 2.4715 (18) Å] and three long distances [Nd—O = 2.830 (2) Å] (Fig. 1; Table 1) are observed. The distances are similar to those reported by Fahey et al. (1985) for the structures of Ca2Nd8(SiO4)6O2 and Ca2.2Nd7.8(SiO4)6O1.9 determined by powder X-ray diffraction.
The O4 atom (O2− ion) is coordinated to three different Nd1/Ca1 ions whilst the SiO44− group has eight contacts to different Nd/Ca positions. The O1 atom coordinates one Nd1/Ca1 position and two Nd2/Ca2 positions, the O2 atom coordinates one Nd1/Ca1 position and two Nd2/Ca2 positions and the O3 position coordinates one Nd1/Ca1 and one Nd2/Ca2 positions. These contacts generate the packing, which can be seen viewed down the c axis in Fig. 2.
3. Synthesis and crystallization
A mixture of appropriate amounts of fine powders of Nd2O3 (99.99%), CaO (99.9%) and SiO2 (99.9%) was put into a sealed Pt-20%Rh tube and heated to 1873 K in an argon atmosphere and maintained at that temperature for 24 h. CaO was made by of CaCO3 at 1373 K for 12 h. The sample was then quenched in a cold-water bath to give a light-blue crystalline solid, from which a single crystal of the title compound was selected. The sample was further analyzed by EPMA–WDS, giving a composition of 20.2% SiO2, 72.1% Nd2O3 and 7.7% CaO. The converted formula according to the EPMA–WDS result was Ca2.45Nd7.45Si6O25.775 (O was calculated).
4. details
Crystal data, data collection and structure . There are two metal positions in the structure and the Nd and Ca ions are disordered on both of these sites. Nd/Ca occupancy on each of the two positions was refined and the occupancy of Nd was found to be 88.7 (5)% for one site and 54.6 (4)% for the other, giving a value of 0.49 for x in Ca2+xNd8–x(SiO4)6O2–0.5x. The occupancy of the anionic O atom was fixed at 2 − 0.5x. Constraints were applied so that the Nd and Ca on the same site had identical positional and displacement parameters.
details are summarized in Table 2
|
Supporting information
CCDC reference: 1447637
10.1107/S205698901600089X/ru2066sup1.cif
contains datablock I. DOI:Structure factors: contains datablock I. DOI: 10.1107/S205698901600089X/ru2066Isup2.hkl
The study of calcium rare earth oxide silicates is important because they are usually observed in nuclear waste along with rare earth silicates. So far, the calcium rare earth oxide silicates of Nd (Fahey et al., 1982, 1985), Sm (PDF 29–365; Smith, 1977), Eu (PDF 29–320; Smith, 1977), Gd (PDF 28–212; Smith, 1976), Tb (PDF 38–256; Lacout, 1986), and Ce (Skakle et al., 2000) have been studied. Fahey et al. (1982, 1985) published the structure and stoichiometry limits of the Ca2 + xNd8 − x(SiO4)2–0.5x system studied using X-ray and neutron powder diffraction. In that study, the samples were synthesized at 1523 or 16873 K and cooled at a rate of 250 K per hour. However, such a slow cooling process may lead to undesired modifications of the obtained specimens since the solubility of calcium does not remain constant but decreases with decreasing temperature. This problem is avoided in the present work by rapid quenching of the Ca2 + xNd8 − x(SiO4)6O2–0.5x samples in their equilibrium state at 1873 K to room temperature within a few s. Consequently, compositions of the samples can be preserved better.
The single-crystal structure recorded at 298 K was found to belong to the
P63/m and have the composition Ca2.49Nd7.51(SiO4)6O1.75 and to be isomorphous with natural apatite and the previously reported Ca2Nd8(SiO4)6O2 and Ca2.2Nd7.8(SiO4)6O1.9 (Fahey et al., 1982, 1985). The solubility limit of calcium in the equilibrium state at 1873 K was found to occur at a composition of Ca2 + xNd8 − x(SiO4)6O2–0.5x, where x = 0.49.There are two metal positions in the
of the structure (Fig. 1) and both contain disordered Nd and Ca ions: Nd1/Ca1 occupies the lower symmetry site 6h and Nd2/Ca2 the higher symmetry site 4f. The occupancies of these metal sites were refined resulting in 0.887 (5)/0.113 (5) for Nd1/Ca1 and 0.546 (4)/0.454 (4) for Nd2/Ca2. The majority (80%) of the Ca is situated at the 4f site. In the structures of Ca2Nd8(SiO4)6O2 and Ca2.2Nd7.8(SiO4)6O1.9, these values are 89 and 73%, respectively (Fahey et al., 1985). The refined value of the amount of Nd in the structure gives a value of 0.49 for x in the equation Ca2 + xNd8 − x(SiO4)6O2–0.5x. For charge balance purposes, the occupancy of O2− in the structure must be 2 − 0.5x or 1.755. Initially, the occupancy of the O2− position O4 in the structure was allowed to refine freely and its value was close to what is required for charge balance; however, it was fixed at 0.146 as the of heavy-atom positions is the most reliable and exact charge balance is required.The Nd1/Ca1 site is seven coordinate and the Nd/Ca—O bond lengths vary between 2.3909 (19) and 2.721 (3) Å for oxygen atoms of the SiO42− unit but the shortest bond distance of 2.2681 (2) Å is to the O2− ion, O4 (Fig. 1; Table 1). The Nd2/Ca2 site is nine coordinate and there only bonds to SiO42− units with six short distances [Nd—O = 2.4231 (17), 2.4715 (18) Å] and three long distances [Nd—O = 2.830 (2) Å] (Fig. 1; Table 1) are observed. The distances are similar to those reported by Fahey et al. (1985) for the structures of Ca2Nd8(SiO4)6O2 and Ca2.2Nd7.8(SiO4)6O1.9 determined by powder X-ray diffraction.
The O4 atom (O2− ion) is coordinated to three different Nd1/Ca1 ions whilst the SiO42− group has eight contacts to different Nd/Ca positions. The O1 atom coordinates one Nd1/Ca1 position and two Nd2/Ca2 positions, the O2 atom coordinates one Nd1/Ca1 position and two Nd2/Ca2 positions and the O3 position coordinates one Nd1/Ca1 and one Nd2/Ca2 positions. These contacts generate the packing, which can be seen viewed down the crystallographic c axis in Fig. 2.
A mixture of appropriate amounts of fine powders of Nd2O3 (99.99%), CaO (99.9%) and SiO2 (99.9%) was put into a sealed Pt-20%Rh tube and heated to 1873 K in an argon atmosphere and maintained at that temperature for 24 h. CaO was made by
of CaCO3 at 1373 K for 12 h. The sample was then quenched in a cold-water bath to give a light-blue crystalline solid, from which a single-crystal of the title compound was selected. The sample was further analyzed by EPMA–WDS, giving a composition of 20.2% SiO2, 72.1% Nd2O3 and 7.7% CaO. The converted formula according to the EPMA–WDS result was Nd7.45Ca2.45Si6O25.775 (O was calculated).Crystal data, data collection and structure
details are summarized in Table 2. There are two metal positions in the structure and the Nd and Ca ions are disordered on both of these sites. Nd/Ca occupancy on each of the two positions was refined and the occupancy of Nd was found to be 88.7 (5)% for one site and 54.6 (4)% for the other, giving a value of 0.49 for x in Ca2 + xNd8 − x(SiO4)6O2–0.5x. The occupancy of the anionic O atom was fixed at 2 − 0.5x. Constraints were applied so that the Nd and Ca on the same site had identical positional and thermal parameters.The study of calcium rare earth oxide silicates is important because they are usually observed in nuclear waste along with rare earth silicates. So far, the calcium rare earth oxide silicates of Nd (Fahey et al., 1982, 1985), Sm (PDF 29–365; Smith, 1977), Eu (PDF 29–320; Smith, 1977), Gd (PDF 28–212; Smith, 1976), Tb (PDF 38–256; Lacout, 1986), and Ce (Skakle et al., 2000) have been studied. Fahey et al. (1982, 1985) published the structure and stoichiometry limits of the Ca2 + xNd8 − x(SiO4)2–0.5x system studied using X-ray and neutron powder diffraction. In that study, the samples were synthesized at 1523 or 16873 K and cooled at a rate of 250 K per hour. However, such a slow cooling process may lead to undesired modifications of the obtained specimens since the solubility of calcium does not remain constant but decreases with decreasing temperature. This problem is avoided in the present work by rapid quenching of the Ca2 + xNd8 − x(SiO4)6O2–0.5x samples in their equilibrium state at 1873 K to room temperature within a few s. Consequently, compositions of the samples can be preserved better.
The single-crystal structure recorded at 298 K was found to belong to the
P63/m and have the composition Ca2.49Nd7.51(SiO4)6O1.75 and to be isomorphous with natural apatite and the previously reported Ca2Nd8(SiO4)6O2 and Ca2.2Nd7.8(SiO4)6O1.9 (Fahey et al., 1982, 1985). The solubility limit of calcium in the equilibrium state at 1873 K was found to occur at a composition of Ca2 + xNd8 − x(SiO4)6O2–0.5x, where x = 0.49.There are two metal positions in the
of the structure (Fig. 1) and both contain disordered Nd and Ca ions: Nd1/Ca1 occupies the lower symmetry site 6h and Nd2/Ca2 the higher symmetry site 4f. The occupancies of these metal sites were refined resulting in 0.887 (5)/0.113 (5) for Nd1/Ca1 and 0.546 (4)/0.454 (4) for Nd2/Ca2. The majority (80%) of the Ca is situated at the 4f site. In the structures of Ca2Nd8(SiO4)6O2 and Ca2.2Nd7.8(SiO4)6O1.9, these values are 89 and 73%, respectively (Fahey et al., 1985). The refined value of the amount of Nd in the structure gives a value of 0.49 for x in the equation Ca2 + xNd8 − x(SiO4)6O2–0.5x. For charge balance purposes, the occupancy of O2− in the structure must be 2 − 0.5x or 1.755. Initially, the occupancy of the O2− position O4 in the structure was allowed to refine freely and its value was close to what is required for charge balance; however, it was fixed at 0.146 as the of heavy-atom positions is the most reliable and exact charge balance is required.The Nd1/Ca1 site is seven coordinate and the Nd/Ca—O bond lengths vary between 2.3909 (19) and 2.721 (3) Å for oxygen atoms of the SiO42− unit but the shortest bond distance of 2.2681 (2) Å is to the O2− ion, O4 (Fig. 1; Table 1). The Nd2/Ca2 site is nine coordinate and there only bonds to SiO42− units with six short distances [Nd—O = 2.4231 (17), 2.4715 (18) Å] and three long distances [Nd—O = 2.830 (2) Å] (Fig. 1; Table 1) are observed. The distances are similar to those reported by Fahey et al. (1985) for the structures of Ca2Nd8(SiO4)6O2 and Ca2.2Nd7.8(SiO4)6O1.9 determined by powder X-ray diffraction.
The O4 atom (O2− ion) is coordinated to three different Nd1/Ca1 ions whilst the SiO42− group has eight contacts to different Nd/Ca positions. The O1 atom coordinates one Nd1/Ca1 position and two Nd2/Ca2 positions, the O2 atom coordinates one Nd1/Ca1 position and two Nd2/Ca2 positions and the O3 position coordinates one Nd1/Ca1 and one Nd2/Ca2 positions. These contacts generate the packing, which can be seen viewed down the crystallographic c axis in Fig. 2.
For synthesis of Ca2 + xNd8 − x(SiO4)2O0.5x, see: Fahey, J. A., Weber, W. J. (1982) and Fahey, J. A., Weber, W. J., and Rotella, F. J. (1985). For structure
of Ca2Nd8(SiO4)2, see: Fahey, J. A., Weber, W. J. (1982). For solubility limits of Ca2 + xNd8 − x(SiO4)2–0.5x, see: Fahey, J. A., Weber, W. J., and Rotella, F. J. (1985).A mixture of appropriate amounts of fine powders of Nd2O3 (99.99%), CaO (99.9%) and SiO2 (99.9%) was put into a sealed Pt-20%Rh tube and heated to 1873 K in an argon atmosphere and maintained at that temperature for 24 h. CaO was made by
of CaCO3 at 1373 K for 12 h. The sample was then quenched in a cold-water bath to give a light-blue crystalline solid, from which a single-crystal of the title compound was selected. The sample was further analyzed by EPMA–WDS, giving a composition of 20.2% SiO2, 72.1% Nd2O3 and 7.7% CaO. The converted formula according to the EPMA–WDS result was Nd7.45Ca2.45Si6O25.775 (O was calculated). detailsCrystal data, data collection and structure
details are summarized in Table 2. There are two metal positions in the structure and the Nd and Ca ions are disordered on both of these sites. Nd/Ca occupancy on each of the two positions was refined and the occupancy of Nd was found to be 88.7 (5)% for one site and 54.6 (4)% for the other, giving a value of 0.49 for x in Ca2 + xNd8 − x(SiO4)6O2–0.5x. The occupancy of the anionic O atom was fixed at 2 − 0.5x. Constraints were applied so that the Nd and Ca on the same site had identical positional and thermal parameters.Data collection: CrysAlis PRO (Agilent, 2012); cell
CrysAlis PRO (Agilent, 2012); data reduction: CrysAlis PRO (Agilent, 2012); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015); molecular graphics: OLEX2 (Dolomanov et al., 2009); software used to prepare material for publication: OLEX2 (Dolomanov et al., 2009) and publCIF (Westrip, 2010).Fig. 1. View of the coordination spheres of the Nd/Ca and Si centres (displacement ellipsoids shown at the 50% probability level; symmetry codes: (i) x, y, −z + 1/2; (ii) y, −x + y, −z; (iii) y, −x + y, z + 1/2; (iv) −y + 1, x − y, z; (v) y − x, −x, −z + 1/2; (vi) y − x, −x, z; (vii) y − x + 1, −x + 1, z; (viii) y, −x + y, z − 1/2; (ix) −y + x + 1, x, z − 1/2; (x) −x + 1, −y + 1, z − 1/2. | |
Fig. 2. View along the crystallographic c axis of the packing arrangement. |
Ca2.49Nd7.51(SiO4)6O1.75 | Dx = 5.256 Mg m−3 |
Mr = 1763.24 | Mo Kα radiation, λ = 0.71073 Å |
Hexagonal, P63/m | Cell parameters from 1649 reflections |
Hall symbol: -P 6c | θ = 4.3–35.5° |
a = 9.5507 (3) Å | µ = 18.18 mm−1 |
c = 7.0513 (3) Å | T = 298 K |
V = 557.03 (3) Å3 | Block, light blue |
Z = 1 | 0.05 × 0.05 × 0.05 mm |
F(000) = 790 |
Agilent SuperNova (single source at offset, Eos detector) diffractometer | 878 independent reflections |
Radiation source: SuperNova (Mo) X-ray Source | 813 reflections with I > 2σ(I) |
Mirror monochromator | Rint = 0.024 |
Detector resolution: 15.9631 pixels mm-1 | θmax = 35.7°, θmin = 3.8° |
ω scans | h = −15→15 |
Absorption correction: multi-scan (CrysAlis PRO; Agilent, 2012) | k = −15→15 |
Tmin = 0.717, Tmax = 1.000 | l = −11→5 |
2616 measured reflections |
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.019 | w = 1/[σ2(Fo2) + (0.0072P)2 + 0.3232P] where P = (Fo2 + 2Fc2)/3 |
wR(F2) = 0.035 | (Δ/σ)max = 0.001 |
S = 1.11 | Δρmax = 0.79 e Å−3 |
878 reflections | Δρmin = −0.86 e Å−3 |
42 parameters | Extinction correction: SHELXL2014 (Sheldrick, 2015), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
0 restraints | Extinction coefficient: 0.0062 (2) |
4 constraints |
Ca2.49Nd7.51(SiO4)6O1.75 | Z = 1 |
Mr = 1763.24 | Mo Kα radiation |
Hexagonal, P63/m | µ = 18.18 mm−1 |
a = 9.5507 (3) Å | T = 298 K |
c = 7.0513 (3) Å | 0.05 × 0.05 × 0.05 mm |
V = 557.03 (3) Å3 |
Agilent SuperNova (single source at offset, Eos detector) diffractometer | 878 independent reflections |
Absorption correction: multi-scan (CrysAlis PRO; Agilent, 2012) | 813 reflections with I > 2σ(I) |
Tmin = 0.717, Tmax = 1.000 | Rint = 0.024 |
2616 measured reflections |
R[F2 > 2σ(F2)] = 0.019 | 42 parameters |
wR(F2) = 0.035 | 0 restraints |
S = 1.11 | Δρmax = 0.79 e Å−3 |
878 reflections | Δρmin = −0.86 e Å−3 |
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) | |
Nd1 | 0.24279 (2) | 0.01102 (2) | 0.2500 | 0.00756 (7) | 0.887 (5) |
Ca1 | 0.24279 (2) | 0.01102 (2) | 0.2500 | 0.00756 (7) | 0.113 (5) |
Nd2 | 0.6667 | 0.3333 | −0.00110 (5) | 0.00906 (10) | 0.546 (4) |
Ca2 | 0.6667 | 0.3333 | −0.00110 (5) | 0.00906 (10) | 0.454 (4) |
Si1 | 0.37185 (11) | 0.40114 (11) | 0.2500 | 0.0077 (2) | |
O1 | 0.4886 (3) | 0.3232 (3) | 0.2500 | 0.0127 (5) | |
O2 | 0.4707 (3) | 0.5974 (3) | 0.2500 | 0.0144 (5) | |
O3 | 0.2528 (2) | 0.3424 (3) | 0.0659 (3) | 0.0209 (5) | |
O4 | 0.0000 | 0.0000 | 0.2500 | 0.0141 (10) | 0.88 |
U11 | U22 | U33 | U12 | U13 | U23 | |
Nd1 | 0.00740 (10) | 0.00713 (10) | 0.00733 (9) | 0.00301 (7) | 0.000 | 0.000 |
Ca1 | 0.00740 (10) | 0.00713 (10) | 0.00733 (9) | 0.00301 (7) | 0.000 | 0.000 |
Nd2 | 0.00913 (12) | 0.00913 (12) | 0.00892 (15) | 0.00456 (6) | 0.000 | 0.000 |
Ca2 | 0.00913 (12) | 0.00913 (12) | 0.00892 (15) | 0.00456 (6) | 0.000 | 0.000 |
Si1 | 0.0069 (4) | 0.0079 (4) | 0.0085 (4) | 0.0039 (3) | 0.000 | 0.000 |
O1 | 0.0116 (12) | 0.0187 (13) | 0.0123 (12) | 0.0108 (10) | 0.000 | 0.000 |
O2 | 0.0120 (12) | 0.0085 (11) | 0.0222 (14) | 0.0049 (9) | 0.000 | 0.000 |
O3 | 0.0158 (9) | 0.0382 (13) | 0.0131 (9) | 0.0166 (9) | −0.0042 (7) | −0.0098 (8) |
O4 | 0.0052 (12) | 0.0052 (12) | 0.032 (3) | 0.0026 (6) | 0.000 | 0.000 |
Nd1—Nd1i | 3.9284 (3) | Si1—Nd2viii | 3.2527 (8) |
Nd1—Nd1ii | 3.9284 (3) | Si1—Nd2xi | 3.2527 (8) |
Nd1—Nd2iii | 4.0666 (3) | Si1—Ca2xi | 3.2527 (8) |
Nd1—Si1 | 3.2877 (9) | Si1—Ca2viii | 3.2527 (8) |
Nd1—Si1i | 3.1738 (9) | Si1—O1 | 1.621 (3) |
Nd1—O1 | 2.721 (3) | Si1—O2 | 1.623 (3) |
Nd1—O2iv | 2.463 (3) | Si1—O3xii | 1.629 (2) |
Nd1—O3v | 2.3909 (19) | Si1—O3 | 1.629 (2) |
Nd1—O3vi | 2.3909 (19) | O1—Nd2iii | 2.4230 (17) |
Nd1—O3i | 2.547 (2) | O1—Ca2iii | 2.4230 (17) |
Nd1—O3vii | 2.547 (2) | O2—Nd1iii | 2.463 (3) |
Nd1—O4 | 2.2681 (2) | O2—Ca1iii | 2.463 (3) |
Nd2—Si1vi | 3.2527 (8) | O2—Nd2viii | 2.4715 (18) |
Nd2—Si1viii | 3.2527 (8) | O2—Nd2xi | 2.4715 (18) |
Nd2—Si1ix | 3.2527 (8) | O2—Ca2xi | 2.4715 (18) |
Nd2—O1iii | 2.4231 (17) | O2—Ca2viii | 2.4715 (18) |
Nd2—O1iv | 2.4231 (17) | O3—Nd1ii | 2.547 (2) |
Nd2—O1 | 2.4230 (17) | O3—Nd1xiii | 2.3909 (19) |
Nd2—O2viii | 2.4715 (18) | O3—Ca1xiii | 2.3909 (19) |
Nd2—O2ix | 2.4715 (18) | O3—Ca1ii | 2.547 (2) |
Nd2—O2vi | 2.4715 (18) | O3—Nd2viii | 2.830 (2) |
Nd2—O3x | 2.830 (2) | O3—Ca2viii | 2.830 (2) |
Nd2—O3viii | 2.830 (2) | O4—Nd1ii | 2.2681 (2) |
Nd2—O3vi | 2.830 (2) | O4—Nd1i | 2.2681 (2) |
Si1—Nd1ii | 3.1738 (9) | O4—Ca1ii | 2.2681 (2) |
Si1—Ca1ii | 3.1738 (9) | O4—Ca1i | 2.2681 (2) |
Nd1ii—Nd1—Nd1i | 60.0 | O3viii—Nd2—Si1ix | 92.88 (4) |
Nd1ii—Nd1—Nd2iii | 103.981 (6) | O3vi—Nd2—Si1viii | 92.88 (4) |
Nd1i—Nd1—Nd2iii | 150.673 (5) | O3vi—Nd2—Si1vi | 30.06 (4) |
Si1—Nd1—Nd1ii | 51.249 (17) | O3x—Nd2—Si1viii | 123.63 (4) |
Si1i—Nd1—Nd1ii | 113.889 (17) | O3vi—Nd2—O3viii | 117.44 (2) |
Si1i—Nd1—Nd1i | 53.889 (17) | O3x—Nd2—O3vi | 117.45 (2) |
Si1—Nd1—Nd1i | 111.249 (17) | O3x—Nd2—O3viii | 117.45 (2) |
Si1—Nd1—Nd2iii | 58.326 (14) | Nd1ii—Si1—Nd1 | 74.86 (2) |
Si1i—Nd1—Nd2iii | 134.034 (14) | Nd1ii—Si1—Nd2viii | 81.18 (2) |
Si1i—Nd1—Si1 | 165.14 (2) | Nd1ii—Si1—Nd2xi | 81.18 (2) |
O1—Nd1—Nd1ii | 80.66 (5) | Nd1ii—Si1—Ca2xi | 81.18 (2) |
O1—Nd1—Nd1i | 140.66 (5) | Nd1ii—Si1—Ca2viii | 81.18 (2) |
O1—Nd1—Nd2iii | 35.26 (3) | Ca1ii—Si1—Nd1 | 74.86 (2) |
O1—Nd1—Si1i | 165.45 (5) | Ca1ii—Si1—Nd1ii | 0.000 (8) |
O1—Nd1—Si1 | 29.41 (5) | Ca1ii—Si1—Nd2xi | 81.18 (2) |
O2iv—Nd1—Nd1i | 120.15 (6) | Ca1ii—Si1—Nd2viii | 81.18 (2) |
O2iv—Nd1—Nd1ii | 179.85 (6) | Ca1ii—Si1—Ca2xi | 81.18 (2) |
O2iv—Nd1—Nd2iii | 75.88 (5) | Ca1ii—Si1—Ca2viii | 81.18 (2) |
O2iv—Nd1—Si1 | 128.60 (6) | Nd2xi—Si1—Nd1 | 139.386 (19) |
O2iv—Nd1—Si1i | 66.27 (6) | Nd2viii—Si1—Nd1 | 139.386 (19) |
O2iv—Nd1—O1 | 99.18 (8) | Nd2xi—Si1—Nd2viii | 65.31 (2) |
O2iv—Nd1—O3i | 71.01 (7) | Nd2xi—Si1—Ca2viii | 65.31 (2) |
O2iv—Nd1—O3vii | 71.01 (7) | Ca2xi—Si1—Nd1 | 139.386 (19) |
O3v—Nd1—Nd1i | 110.42 (6) | Ca2viii—Si1—Nd1 | 139.386 (19) |
O3i—Nd1—Nd1i | 58.32 (5) | Ca2xi—Si1—Nd2xi | 0.000 (10) |
O3v—Nd1—Nd1ii | 94.99 (5) | Ca2viii—Si1—Nd2viii | 0.000 (10) |
O3vi—Nd1—Nd1i | 110.42 (6) | Ca2xi—Si1—Nd2viii | 65.31 (2) |
O3i—Nd1—Nd1ii | 109.12 (5) | Ca2xi—Si1—Ca2viii | 65.31 (2) |
O3vii—Nd1—Nd1ii | 109.12 (5) | O1—Si1—Nd1 | 55.53 (10) |
O3vii—Nd1—Nd1i | 58.32 (5) | O1—Si1—Nd1ii | 130.39 (10) |
O3vi—Nd1—Nd1ii | 94.99 (5) | O1—Si1—Ca1ii | 130.39 (10) |
O3vi—Nd1—Nd2iii | 94.52 (6) | O1—Si1—Nd2xi | 136.87 (6) |
O3i—Nd1—Nd2iii | 112.89 (5) | O1—Si1—Nd2viii | 136.87 (6) |
O3vii—Nd1—Nd2iii | 146.38 (5) | O1—Si1—Ca2viii | 136.87 (6) |
O3v—Nd1—Nd2iii | 42.90 (6) | O1—Si1—Ca2xi | 136.87 (6) |
O3v—Nd1—Si1 | 77.25 (5) | O1—Si1—O2 | 113.16 (14) |
O3vi—Nd1—Si1i | 106.70 (5) | O1—Si1—O3 | 111.34 (9) |
O3i—Nd1—Si1i | 30.67 (4) | O1—Si1—O3xii | 111.34 (9) |
O3i—Nd1—Si1 | 145.64 (5) | O2—Si1—Nd1ii | 116.45 (10) |
O3vii—Nd1—Si1i | 30.67 (4) | O2—Si1—Nd1 | 168.69 (10) |
O3v—Nd1—Si1i | 106.70 (5) | O2—Si1—Ca1ii | 116.45 (10) |
O3vii—Nd1—Si1 | 145.64 (5) | O2—Si1—Nd2viii | 47.71 (6) |
O3vi—Nd1—Si1 | 77.25 (5) | O2—Si1—Nd2xi | 47.70 (6) |
O3v—Nd1—O1 | 70.49 (5) | O2—Si1—Ca2xi | 47.70 (6) |
O3i—Nd1—O1 | 146.95 (5) | O2—Si1—Ca2viii | 47.71 (6) |
O3vi—Nd1—O1 | 70.49 (5) | O2—Si1—O3xii | 107.49 (10) |
O3vii—Nd1—O1 | 146.95 (5) | O2—Si1—O3 | 107.49 (10) |
O3vi—Nd1—O2iv | 84.96 (5) | O3xii—Si1—Nd1ii | 52.89 (7) |
O3v—Nd1—O2iv | 84.96 (5) | O3xii—Si1—Nd1 | 78.94 (9) |
O3vii—Nd1—O3i | 61.28 (9) | O3—Si1—Nd1ii | 52.89 (7) |
O3vi—Nd1—O3vii | 77.13 (4) | O3—Si1—Nd1 | 78.94 (9) |
O3vi—Nd1—O3i | 136.63 (7) | O3—Si1—Ca1ii | 52.89 (7) |
O3v—Nd1—O3vii | 136.63 (7) | O3xii—Si1—Ca1ii | 52.89 (7) |
O3v—Nd1—O3i | 77.13 (4) | O3xii—Si1—Nd2xi | 60.46 (9) |
O3v—Nd1—O3vi | 137.40 (11) | O3—Si1—Nd2xi | 111.52 (8) |
O4—Nd1—Nd1i | 30.0 | O3xii—Si1—Nd2viii | 111.52 (8) |
O4—Nd1—Nd1ii | 30.0 | O3—Si1—Nd2viii | 60.46 (9) |
O4—Nd1—Nd2iii | 130.005 (6) | O3xii—Si1—Ca2xi | 60.46 (9) |
O4—Nd1—Si1 | 81.249 (17) | O3xii—Si1—Ca2viii | 111.52 (8) |
O4—Nd1—Si1i | 83.888 (17) | O3—Si1—Ca2xi | 111.52 (8) |
O4—Nd1—O1 | 110.66 (5) | O3—Si1—Ca2viii | 60.46 (9) |
O4—Nd1—O2iv | 150.15 (6) | O3xii—Si1—O3 | 105.63 (15) |
O4—Nd1—O3vi | 104.58 (5) | Nd2iii—O1—Nd1 | 104.33 (7) |
O4—Nd1—O3vii | 83.45 (5) | Nd2—O1—Nd1 | 104.33 (7) |
O4—Nd1—O3i | 83.45 (5) | Nd2iii—O1—Nd2 | 93.89 (9) |
O4—Nd1—O3v | 104.58 (5) | Ca2iii—O1—Nd1 | 104.33 (7) |
Si1vi—Nd2—Si1viii | 93.628 (14) | Ca2iii—O1—Nd2 | 93.89 (9) |
Si1ix—Nd2—Si1viii | 93.628 (14) | Ca2iii—O1—Nd2iii | 0.000 (11) |
Si1ix—Nd2—Si1vi | 93.628 (14) | Si1—O1—Nd1 | 95.06 (11) |
O1iv—Nd2—Si1ix | 98.07 (6) | Si1—O1—Nd2 | 127.73 (7) |
O1iii—Nd2—Si1vi | 165.42 (5) | Si1—O1—Nd2iii | 127.73 (7) |
O1iv—Nd2—Si1vi | 94.28 (5) | Si1—O1—Ca2iii | 127.73 (7) |
O1—Nd2—Si1vi | 98.07 (6) | Nd1iii—O2—Nd2viii | 115.89 (7) |
O1iii—Nd2—Si1viii | 98.07 (6) | Nd1iii—O2—Nd2xi | 115.89 (7) |
O1iv—Nd2—Si1viii | 165.42 (5) | Nd1iii—O2—Ca2viii | 115.89 (7) |
O1iii—Nd2—Si1ix | 94.28 (5) | Nd1iii—O2—Ca2xi | 115.89 (7) |
O1—Nd2—Si1ix | 165.42 (5) | Ca1iii—O2—Nd1iii | 0.000 (9) |
O1—Nd2—Si1viii | 94.28 (5) | Ca1iii—O2—Nd2xi | 115.89 (7) |
O1iii—Nd2—O1 | 72.49 (7) | Ca1iii—O2—Nd2viii | 115.89 (7) |
O1iv—Nd2—O1iii | 72.49 (7) | Ca1iii—O2—Ca2xi | 115.89 (7) |
O1iv—Nd2—O1 | 72.49 (7) | Ca1iii—O2—Ca2viii | 115.89 (7) |
O1—Nd2—O2vi | 125.79 (8) | Nd2xi—O2—Nd2viii | 90.49 (8) |
O1iv—Nd2—O2vi | 94.22 (6) | Nd2xi—O2—Ca2viii | 90.49 (8) |
O1—Nd2—O2ix | 153.93 (8) | Nd2viii—O2—Ca2viii | 0.0 |
O1iv—Nd2—O2viii | 153.93 (8) | Ca2xi—O2—Nd2viii | 90.49 (8) |
O1iii—Nd2—O2ix | 94.22 (6) | Ca2xi—O2—Nd2xi | 0.0 |
O1iii—Nd2—O2vi | 153.93 (8) | Ca2xi—O2—Ca2viii | 90.49 (8) |
O1iv—Nd2—O2ix | 125.79 (8) | Si1—O2—Nd1iii | 122.72 (13) |
O1—Nd2—O2viii | 94.22 (6) | Si1—O2—Ca1iii | 122.72 (13) |
O1iii—Nd2—O2viii | 125.79 (8) | Si1—O2—Nd2xi | 103.23 (9) |
O1iii—Nd2—O3vi | 139.76 (6) | Si1—O2—Nd2viii | 103.23 (9) |
O1—Nd2—O3viii | 87.87 (7) | Si1—O2—Ca2xi | 103.23 (9) |
O1iv—Nd2—O3x | 68.15 (7) | Si1—O2—Ca2viii | 103.23 (9) |
O1—Nd2—O3vi | 68.15 (7) | Nd1xiii—O3—Nd1ii | 116.16 (8) |
O1iii—Nd2—O3x | 87.87 (7) | Nd1xiii—O3—Ca1ii | 116.16 (8) |
O1iv—Nd2—O3viii | 139.76 (6) | Nd1ii—O3—Nd2viii | 101.98 (7) |
O1iv—Nd2—O3vi | 87.87 (7) | Nd1xiii—O3—Nd2viii | 101.99 (8) |
O1iii—Nd2—O3viii | 68.15 (7) | Nd1ii—O3—Ca2viii | 101.98 (7) |
O1—Nd2—O3x | 139.76 (6) | Nd1xiii—O3—Ca2viii | 101.99 (8) |
O2vi—Nd2—Si1ix | 64.81 (6) | Ca1ii—O3—Nd1ii | 0.000 (14) |
O2ix—Nd2—Si1viii | 64.81 (6) | Ca1xiii—O3—Nd1xiii | 0.0 |
O2ix—Nd2—Si1vi | 98.63 (5) | Ca1xiii—O3—Nd1ii | 116.16 (8) |
O2ix—Nd2—Si1ix | 29.07 (6) | Ca1xiii—O3—Ca1ii | 116.16 (8) |
O2viii—Nd2—Si1viii | 29.07 (6) | Ca1ii—O3—Nd2viii | 101.98 (7) |
O2viii—Nd2—Si1ix | 98.63 (5) | Ca1xiii—O3—Nd2viii | 101.99 (8) |
O2viii—Nd2—Si1vi | 64.81 (6) | Ca1ii—O3—Ca2viii | 101.98 (7) |
O2vi—Nd2—Si1vi | 29.07 (6) | Ca1xiii—O3—Ca2viii | 101.99 (8) |
O2vi—Nd2—Si1viii | 98.63 (5) | Ca2viii—O3—Nd2viii | 0.000 (14) |
O2vi—Nd2—O2viii | 75.14 (6) | Si1—O3—Nd1xiii | 141.68 (11) |
O2vi—Nd2—O2ix | 75.14 (6) | Si1—O3—Nd1ii | 96.43 (9) |
O2ix—Nd2—O2viii | 75.14 (6) | Si1—O3—Ca1xiii | 141.68 (11) |
O2vi—Nd2—O3viii | 125.24 (6) | Si1—O3—Ca1ii | 96.43 (9) |
O2vi—Nd2—O3x | 66.19 (7) | Si1—O3—Nd2viii | 89.48 (10) |
O2viii—Nd2—O3viii | 58.84 (7) | Si1—O3—Ca2viii | 89.48 (10) |
O2ix—Nd2—O3x | 58.84 (7) | Nd1i—O4—Nd1ii | 120.0 |
O2vi—Nd2—O3vi | 58.85 (7) | Nd1—O4—Nd1ii | 120.0 |
O2viii—Nd2—O3x | 125.24 (6) | Nd1—O4—Nd1i | 120.0 |
O2ix—Nd2—O3viii | 66.19 (7) | Nd1—O4—Ca1ii | 120.0 |
O2ix—Nd2—O3vi | 125.24 (6) | Nd1i—O4—Ca1ii | 120.0 |
O2viii—Nd2—O3vi | 66.19 (7) | Nd1—O4—Ca1i | 120.0 |
O3vi—Nd2—Si1ix | 123.63 (4) | Ca1i—O4—Nd1i | 0.000 (16) |
O3viii—Nd2—Si1viii | 30.06 (4) | Ca1ii—O4—Nd1ii | 0.000 (9) |
O3x—Nd2—Si1ix | 30.06 (4) | Ca1i—O4—Nd1ii | 120.0 |
O3x—Nd2—Si1vi | 92.88 (4) | Ca1i—O4—Ca1ii | 120.0 |
O3viii—Nd2—Si1vi | 123.63 (4) |
Symmetry codes: (i) −x+y, −x, −z+1/2; (ii) −y, x−y, z; (iii) −x+y+1, −x+1, −z+1/2; (iv) −y+1, x−y, z; (v) y, −x+y, z+1/2; (vi) y, −x+y, −z; (vii) −x+y, −x, z; (viii) −x+1, −y+1, −z; (ix) x−y+1, x, z−1/2; (x) x−y+1, x, −z; (xi) x−y, x, z+1/2; (xii) x, y, −z+1/2; (xiii) x−y, x, z−1/2. |
Nd1—O1 | 2.721 (3) | Nd2—O2iv | 2.4715 (18) |
Nd1—O2i | 2.463 (3) | Nd2—O3v | 2.830 (2) |
Nd1—O3ii | 2.3909 (19) | Si1—O1 | 1.621 (3) |
Nd1—O3iii | 2.547 (2) | Si1—O2 | 1.623 (3) |
Nd1—O4 | 2.2681 (2) | Si1—O3vi | 1.629 (2) |
Nd2—O1i | 2.4231 (17) |
Symmetry codes: (i) −y+1, x−y, z; (ii) y, −x+y, z+1/2; (iii) −x+y, −x, −z+1/2; (iv) x−y+1, x, z−1/2; (v) −x+1, −y+1, −z; (vi) x, y, −z+1/2. |
Experimental details
Crystal data | |
Chemical formula | Ca2.49Nd7.51(SiO4)6O1.75 |
Mr | 1763.24 |
Crystal system, space group | Hexagonal, P63/m |
Temperature (K) | 298 |
a, c (Å) | 9.5507 (3), 7.0513 (3) |
V (Å3) | 557.03 (3) |
Z | 1 |
Radiation type | Mo Kα |
µ (mm−1) | 18.18 |
Crystal size (mm) | 0.05 × 0.05 × 0.05 |
Data collection | |
Diffractometer | Agilent SuperNova (single source at offset, Eos detector) |
Absorption correction | Multi-scan (CrysAlis PRO; Agilent, 2012) |
Tmin, Tmax | 0.717, 1.000 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 2616, 878, 813 |
Rint | 0.024 |
(sin θ/λ)max (Å−1) | 0.821 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.019, 0.035, 1.11 |
No. of reflections | 878 |
No. of parameters | 42 |
Δρmax, Δρmin (e Å−3) | 0.79, −0.86 |
Computer programs: CrysAlis PRO (Agilent, 2012), SHELXS97 (Sheldrick, 2008), SHELXL2014 (Sheldrick, 2015), OLEX2 (Dolomanov et al., 2009) and publCIF (Westrip, 2010).
Acknowledgements
The authors thank the Hercules Foundation for supporting the purchase of the diffractometer through project AKUL/09/0035.
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