
Supporting information
![]() | Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536803004872/br6086sup1.cif |
![]() | Structure factor file (CIF format) https://doi.org/10.1107/S1600536803004872/br6086Isup2.hkl |
The title compound crystallized as a very minor component from an Li-rich flux (experimental parameters: 0.6 g LiF, 1.67 g MoO3, 0.1726 g Sc2O3, 0.1276 g A l2O3, 0.1999 g TiO2; Pt crucible covered with a lid, Tmax = 1423 K, holding time 6 h, cooling rate 1.5 K min-1, Tmin = 1173 K, slow cooling to room temperature after switching off furnace). Li3Sc(MoO4)3 formed colourless-to-white acicular crystals (up to ca 0.5 mm in length), often in bundle-like subparallel intergrowths. The crystals were accompanied by large amounts of LiAl5O8 (colourless sharp octahedra), and minor amounts of an Al-rich member of the solid-solution series Sc2TiO5—Al2TiO5 (Kolitsch & Tillmanns, 2003). Chemical analyses of the title compound with standard semiquantitative SEM-EDS showed the presence of only Sc and Mo (Li cannot be detected under these conditions).
A freely refined model gave Li:Sc occupancy ratios of 0.639 (3):0.361 (3), 0.751 (3):0.249 (3) and 0.925 (3):0.075 (3) for the Li1, Li2 and Li3 sites, respectively, which would correspond to 5.88 positive charges and 6.00 negative charges in the formula unit. However, the Li1 and, to a lesser extent, the Li3 site show somewhat anisotropic displacement parameters, an observation which indicates that refined Li:Sc occupancy ratios are certainly influenced by the anisotropic behavior of the atoms on these sites (neglecting all other possible influences). In the final refinement, the Li:Sc ratio on the Li1 site was slightly modified and fixed at 58:42, in order to achieve a charge-balanced formula.
Data collection: COLLECT (Nonius, 2002); cell refinement: HKL SCALEPACK (Otwinowski & Mino, 1997); data reduction: HKL DENZO (Otwinowski & Mino, 1997) and SCALEPACK; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ATOMS (Shape Software, 1999) and ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: SHELXL97.
Li3Mo3O12Sc | F(000) = 1008 |
Mr = 545.60 | Dx = 3.770 Mg m−3 |
Orthorhombic, Pnma | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2ac 2n | Cell parameters from 1670 reflections |
a = 5.130 (1) Å | θ = 2.0–30.0° |
b = 10.560 (2) Å | µ = 4.56 mm−1 |
c = 17.745 (4) Å | T = 293 K |
V = 961.3 (3) Å3 | Fragment, colorless |
Z = 4 | 0.10 × 0.05 × 0.05 mm |
Nonius KappaCCD diffractometer | 1477 independent reflections |
Radiation source: fine-focus sealed tube | 1326 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.011 |
ψ and ω scans | θmax = 30.1°, θmin = 2.3° |
Absorption correction: multi-scan (HKL SCALEPACK; Otwinowski & Minor, 1997) | h = −7→7 |
Tmin = 0.659, Tmax = 0.804 | k = −14→14 |
2635 measured reflections | l = −24→24 |
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)] = 0.023 | w = 1/[σ2(Fo2) + (0.024P)2 + 2P] where P = (Fo2 + 2Fc2)/3 |
wR(F2) = 0.058 | (Δ/σ)max = 0.001 |
S = 1.12 | Δρmax = 0.96 e Å−3 |
1477 reflections | Δρmin = −0.84 e Å−3 |
99 parameters | Extinction correction: SHELXL97, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
2 restraints | Extinction coefficient: 0.0018 (3) |
Li3Mo3O12Sc | V = 961.3 (3) Å3 |
Mr = 545.60 | Z = 4 |
Orthorhombic, Pnma | Mo Kα radiation |
a = 5.130 (1) Å | µ = 4.56 mm−1 |
b = 10.560 (2) Å | T = 293 K |
c = 17.745 (4) Å | 0.10 × 0.05 × 0.05 mm |
Nonius KappaCCD diffractometer | 1477 independent reflections |
Absorption correction: multi-scan (HKL SCALEPACK; Otwinowski & Minor, 1997) | 1326 reflections with I > 2σ(I) |
Tmin = 0.659, Tmax = 0.804 | Rint = 0.011 |
2635 measured reflections |
R[F2 > 2σ(F2)] = 0.023 | 99 parameters |
wR(F2) = 0.058 | 2 restraints |
S = 1.12 | Δρmax = 0.96 e Å−3 |
1477 reflections | Δρmin = −0.84 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) | |
Mo1 | 0.27559 (5) | 0.52755 (2) | 0.156515 (13) | 0.01468 (9) | |
Mo2 | 0.77812 (6) | 0.2500 | 0.057110 (18) | 0.01320 (10) | |
Li1 | 0.1048 (5) | 0.2500 | 0.25027 (10) | 0.0289 (4) | 0.58 |
Sc1 | 0.1048 (5) | 0.2500 | 0.25027 (10) | 0.0289 (4) | 0.42 |
Li2 | 0.7547 (3) | 0.57420 (15) | 0.02731 (9) | 0.0129 (4) | 0.751 (3) |
Sc2 | 0.7547 (3) | 0.57420 (15) | 0.02731 (9) | 0.0129 (4) | 0.249 (3) |
Li3 | 0.2446 (9) | 0.7500 | 0.3018 (3) | 0.0237 (13) | 0.925 (3) |
Sc3 | 0.2446 (9) | 0.7500 | 0.3018 (3) | 0.0237 (13) | 0.075 (3) |
O1 | 0.8588 (6) | 0.2500 | 0.15432 (16) | 0.0201 (6) | |
O2 | 0.0531 (6) | 0.2500 | −0.00495 (16) | 0.0194 (6) | |
O3 | 0.5831 (4) | 0.1167 (2) | 0.03722 (11) | 0.0201 (4) | |
O4 | 0.0838 (4) | 0.4902 (2) | 0.07587 (11) | 0.0199 (4) | |
O5 | 0.0797 (4) | 0.6233 (2) | 0.21271 (12) | 0.0240 (5) | |
O6 | 0.3528 (4) | 0.38437 (19) | 0.20513 (11) | 0.0195 (4) | |
O7 | 0.5554 (4) | 0.61262 (19) | 0.12713 (12) | 0.0208 (4) |
U11 | U22 | U33 | U12 | U13 | U23 | |
Mo1 | 0.01428 (14) | 0.01484 (14) | 0.01493 (14) | 0.00046 (8) | −0.00045 (8) | 0.00130 (8) |
Mo2 | 0.01243 (16) | 0.01373 (17) | 0.01345 (16) | 0.000 | 0.00018 (11) | 0.000 |
Li1 | 0.0522 (12) | 0.0172 (7) | 0.0172 (8) | 0.000 | 0.0012 (8) | 0.000 |
Sc1 | 0.0522 (12) | 0.0172 (7) | 0.0172 (8) | 0.000 | 0.0012 (8) | 0.000 |
Li2 | 0.0112 (7) | 0.0150 (8) | 0.0125 (8) | 0.0003 (5) | 0.0007 (5) | 0.0022 (6) |
Sc2 | 0.0112 (7) | 0.0150 (8) | 0.0125 (8) | 0.0003 (5) | 0.0007 (5) | 0.0022 (6) |
Li3 | 0.017 (2) | 0.023 (3) | 0.031 (3) | 0.000 | 0.0049 (18) | 0.000 |
Sc3 | 0.017 (2) | 0.023 (3) | 0.031 (3) | 0.000 | 0.0049 (18) | 0.000 |
O1 | 0.0230 (15) | 0.0185 (14) | 0.0189 (14) | 0.000 | −0.0035 (11) | 0.000 |
O2 | 0.0171 (14) | 0.0184 (13) | 0.0227 (14) | 0.000 | 0.0026 (11) | 0.000 |
O3 | 0.0180 (10) | 0.0219 (10) | 0.0203 (10) | −0.0021 (8) | −0.0015 (8) | −0.0009 (8) |
O4 | 0.0167 (10) | 0.0240 (10) | 0.0190 (9) | 0.0011 (8) | −0.0006 (8) | 0.0014 (8) |
O5 | 0.0226 (11) | 0.0256 (11) | 0.0237 (10) | 0.0031 (9) | 0.0005 (8) | −0.0030 (9) |
O6 | 0.0208 (10) | 0.0196 (10) | 0.0183 (9) | 0.0005 (8) | −0.0006 (8) | 0.0019 (8) |
O7 | 0.0203 (10) | 0.0209 (10) | 0.0210 (10) | −0.0030 (8) | 0.0007 (8) | −0.0005 (8) |
Mo1—O5 | 1.740 (2) | Li1—O1iv | 2.136 (4) |
Mo1—O7 | 1.772 (2) | Li2—O7 | 2.085 (3) |
Mo1—O4 | 1.781 (2) | Li2—O4ii | 2.093 (3) |
Mo1—O6 | 1.785 (2) | Li2—O4vi | 2.122 (3) |
Mo2—O3 | 1.762 (2) | Li2—O3vii | 2.125 (2) |
Mo2—O3i | 1.762 (2) | Li2—O2vi | 2.139 (2) |
Mo2—O1 | 1.774 (3) | Li2—O3i | 2.207 (3) |
Mo2—O2ii | 1.790 (3) | Li3—O7viii | 2.153 (4) |
Li1—O6 | 2.067 (3) | Li3—O7iv | 2.153 (4) |
Li1—O6i | 2.067 (3) | Li3—O5ix | 2.193 (4) |
Li1—O6iii | 2.076 (3) | Li3—O5x | 2.193 (4) |
Li1—O6iv | 2.076 (3) | Li3—O5 | 2.237 (5) |
Li1—O1v | 2.119 (4) | Li3—O5xi | 2.237 (5) |
O5—Mo1—O7 | 109.99 (10) | O4ii—Li2—O4vi | 84.51 (10) |
O5—Mo1—O4 | 105.68 (10) | O7—Li2—O3vii | 90.97 (10) |
O7—Mo1—O4 | 108.86 (10) | O4ii—Li2—O3vii | 165.77 (12) |
O5—Mo1—O6 | 110.09 (10) | O4vi—Li2—O3vii | 85.48 (10) |
O7—Mo1—O6 | 113.08 (10) | O7—Li2—O2vi | 102.40 (11) |
O4—Mo1—O6 | 108.87 (9) | O4ii—Li2—O2vi | 94.14 (11) |
O3—Mo2—O3i | 105.98 (14) | O4vi—Li2—O2vi | 86.46 (11) |
O3—Mo2—O1 | 109.10 (9) | O3vii—Li2—O2vi | 95.31 (11) |
O3i—Mo2—O1 | 109.10 (9) | O7—Li2—O3i | 85.10 (9) |
O3—Mo2—O2ii | 108.92 (9) | O4ii—Li2—O3i | 84.36 (10) |
O3i—Mo2—O2ii | 108.92 (9) | O4vi—Li2—O3i | 86.08 (10) |
O1—Mo2—O2ii | 114.49 (14) | O3vii—Li2—O3i | 84.89 (10) |
O6—Li1—O6i | 86.70 (14) | O2vi—Li2—O3i | 172.49 (12) |
O6—Li1—O6iii | 179.42 (14) | O7viii—Li3—O7iv | 84.7 (2) |
O6i—Li1—O6iii | 93.54 (9) | O7viii—Li3—O5ix | 90.64 (12) |
O6—Li1—O6iv | 93.54 (9) | O7iv—Li3—O5ix | 146.4 (3) |
O6i—Li1—O6iv | 179.42 (15) | O7viii—Li3—O5x | 146.4 (3) |
O6iii—Li1—O6iv | 86.21 (14) | O7iv—Li3—O5x | 90.64 (12) |
O6—Li1—O1v | 93.16 (11) | O5ix—Li3—O5x | 75.16 (18) |
O6i—Li1—O1v | 93.16 (11) | O7viii—Li3—O5 | 130.3 (2) |
O6iii—Li1—O1v | 86.29 (11) | O7iv—Li3—O5 | 80.82 (12) |
O6iv—Li1—O1v | 86.29 (11) | O5ix—Li3—O5 | 125.3 (2) |
O6—Li1—O1iv | 86.09 (11) | O5x—Li3—O5 | 81.30 (13) |
O6i—Li1—O1iv | 86.09 (11) | O7viii—Li3—O5xi | 80.82 (12) |
O6iii—Li1—O1iv | 94.46 (10) | O7iv—Li3—O5xi | 130.3 (2) |
O6iv—Li1—O1iv | 94.46 (10) | O5ix—Li3—O5xi | 81.30 (13) |
O1v—Li1—O1iv | 178.97 (18) | O5x—Li3—O5xi | 125.3 (2) |
O7—Li2—O4ii | 97.36 (10) | O5—Li3—O5xi | 73.4 (2) |
O7—Li2—O4vi | 170.75 (12) |
Symmetry codes: (i) x, −y+1/2, z; (ii) x+1, y, z; (iii) x−1/2, −y+1/2, −z+1/2; (iv) x−1/2, y, −z+1/2; (v) x−1, y, z; (vi) −x+1, −y+1, −z; (vii) −x+1, y+1/2, −z; (viii) x−1/2, −y+3/2, −z+1/2; (ix) x+1/2, −y+3/2, −z+1/2; (x) x+1/2, y, −z+1/2; (xi) x, −y+3/2, z. |
Experimental details
Crystal data | |
Chemical formula | Li3Mo3O12Sc |
Mr | 545.60 |
Crystal system, space group | Orthorhombic, Pnma |
Temperature (K) | 293 |
a, b, c (Å) | 5.130 (1), 10.560 (2), 17.745 (4) |
V (Å3) | 961.3 (3) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 4.56 |
Crystal size (mm) | 0.10 × 0.05 × 0.05 |
Data collection | |
Diffractometer | Nonius KappaCCD diffractometer |
Absorption correction | Multi-scan (HKL SCALEPACK; Otwinowski & Minor, 1997) |
Tmin, Tmax | 0.659, 0.804 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 2635, 1477, 1326 |
Rint | 0.011 |
(sin θ/λ)max (Å−1) | 0.705 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.023, 0.058, 1.12 |
No. of reflections | 1477 |
No. of parameters | 99 |
No. of restraints | 2 |
Δρmax, Δρmin (e Å−3) | 0.96, −0.84 |
Computer programs: COLLECT (Nonius, 2002), HKL SCALEPACK (Otwinowski & Mino, 1997), HKL DENZO (Otwinowski & Mino, 1997) and SCALEPACK, SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), ATOMS (Shape Software, 1999) and ORTEP-3 for Windows (Farrugia, 1997), SHELXL97.
Mo1—O5 | 1.740 (2) | Li1—O1iv | 2.136 (4) |
Mo1—O7 | 1.772 (2) | Li2—O7 | 2.085 (3) |
Mo1—O4 | 1.781 (2) | Li2—O4i | 2.093 (3) |
Mo1—O6 | 1.785 (2) | Li2—O4v | 2.122 (3) |
Mo2—O3 | 1.762 (2) | Li2—O3vi | 2.125 (2) |
Mo2—O1 | 1.774 (3) | Li2—O2v | 2.139 (2) |
Mo2—O2i | 1.790 (3) | Li2—O3vii | 2.207 (3) |
Li1—O6 | 2.067 (3) | Li3—O7viii | 2.153 (4) |
Li1—O6ii | 2.076 (3) | Li3—O5ix | 2.193 (4) |
Li1—O1iii | 2.119 (4) | Li3—O5 | 2.237 (5) |
Symmetry codes: (i) x+1, y, z; (ii) x−1/2, −y+1/2, −z+1/2; (iii) x−1, y, z; (iv) x−1/2, y, −z+1/2; (v) −x+1, −y+1, −z; (vi) −x+1, y+1/2, −z; (vii) x, −y+1/2, z; (viii) x−1/2, −y+3/2, −z+1/2; (ix) x+1/2, −y+3/2, −z+1/2. |
During flux-growth preparation in air of compounds in the system Sc2O3–Al2O3–TiO2–SiO2, the title compound was obtained as a by-product from an Li-rich molybdate flux. Li3Sc(MoO4)3 crystallizes in space group Pnma and is isotypic with Li3Fe(MoO4)3 (Klevtsova & Magarill, 1970). The pale-green FeIII member forms a solid solution series with black Li2FeII2(MoO4)3 (Klevtsov, 1970; Klevtsova & Magarill, 1970). In fact, a number of isotypic (space group Pnma) Li3MIII(MoO4)3 and Li2MII2(MoO4)3 compounds are known, although the crystal structures of the MIII members have only been refined for the above-mentioned FeIII representative.
Li3MIII(MoO4)3 members with MIII = Fe, Al, Sc, Ga, In, and Cr were prepared by Klevtsov (1970) and Trunov & Efremov (1971). The In member has also been studied by Velikodnyi et al. (1970). Li3Cr(MoO4)3 has been further characterized by Butukhanov et al. (1972), Trunov & Velikodnyi (1972), and Mokhosoev et al. (1973), and the members for MIII = Al and In were described by Kozhevnikova et al. (1980). Li3Ga(MoO4)3 was observed by Alekseev et al. (1982) as one of the products of the reaction between Li2MoO4 and Ga2(SO4)3. Porotnikov et al. (1982) prepared Li3Sc(MoO4)3 and stated that it melts congruently at 1109 K, and decomposes to Li2MoO4 and LiSc(MoO4)2 at less than 810 K. IR spectroscopic studies of Li3MIII(MoO4)3 members with MIII = Al, In, Cr, Fe, and Co were reported by Juri et al. (1984, 1992).
Li2MII2(MoO4)3 compounds with MII = Mg, Fe, Co, Ni, Cu, and Zn have been prepared by Efremov & Trunov (1975) and Penkova & Klevtsov (1977). Independently of the latter authors, the structure of Li2Ni2(MoO4)3 was reported by Ozima et al. (1977), who also presented a detailed discussion of the structure type. [Note that the z coordinate for the site designated `M1–Li' is misprinted in the original publication on Li2Ni2(MoO4)3 (Ozima et al., 1977), and also in the ICSD entry 1082 (Belsky et al., 2002) for this structure; the correct value, found by trial and error, must be 0.7568 (instead of 0.5568).] The crystal structure of Li2–2xMn2 + x(MoO4)3 (x = 1/5) was determined by Solodovnikov et al. (1994), and Li2Co2(MoO4)3 was structurally characterized by Wiesmann et al. (1995). Results from both studies confirm the previous results of Ozima et al. (1977).
Li2Cu2(MoO4)3 was reported to have the monoclinic space group P21/c (Wiesmann et al., 1994), but a close examination showed that the topology is identical to that of the Pnma-type Li2MII2(MoO4)3 compounds, and a search for higher symmetry using PLATON (Spek, 2000, 2003) clearly suggested that the correct space group for Li2Cu2(MoO4)3 is probably also Pnma. A dimorph of Li2Fe2(MoO4)3, garnet-related and crystallizing in space group Pbcn, was structurally characterized by Torardi & Prince (1986) and Torardi et al. (1988). We also point out that `NaCo2.31(MoO4)3' (Ibers & Smith, 1964; later shown to be rather Na2CoII2(MoO4)3 by Klevtsova & Magarill, 1970) is isostructural with the Pnma-type Li3MIII(MoO4)3 and Li2MII2(MoO4)3 compounds listed above, and in fact represents the first solution of the common crystal structure.
The atomic arrangement in Li3Sc(MoO4)3 is based on a three-dimensional framework of (Li,Sc)O6 polyhedra linked to MoO4 tetrahedra (Figs. 1–3). There are two distinct types of (Li,Sc)O6 polyhedra: the first two (Li,Sc) sites, Li1 and Li2, show a nearly regular octahedral coordination (Table 1), whereas the third site, Li3, has a regular trigonal-prismatic environment (Figs. 1 and 2). The Li1 and Li2 sites contain about 42 and 25% Sc, whereas the trigonal-prismatic site (Li3) contains only about 8% Sc. The average (Li,Sc)—O bond lengths for the octahedrally coordinated Li1 and Li2 sites are 2.092 and 2.129 Å, respectively, whereas the corresponding value in the trigonal-prismatic (Li3,Sc)O6 polyhedron is 2.195 Å. Thus, an increasing Li content on a specific sites causes a slight increase in average (Li,Sc)—O bond lengths, if the influences of the polyhedral geometry and distortion are neglected. This increase is in agreement with literature data on the size and geometry of LiO6 and ScO6 polyhedra; the average Li—O bond length for (more or less) octahedrally coordinated Li sites in a large number of oxidic Li compounds was calculated to be 2.15 Å (Wenger & Armbruster, 1991), whereas octahedrally coordinated Sc has an average Sc—O bond length of 2.105 Å (Baur, 1981). In Li3Fe(MoO4)3 (Klevtsova & Magarill, 1970), the corresponding values for the (Li1,Fe), (Li2,Fe), and (Li3,Fe) sites are 2.046, 2.091, and 2.164 Å, respectively. Thus, the overall trend is identical.
A closer look at the connectivity within the framework structure of the title compound (Figs. 1 and 2) shows that it contains chains of face-sharing fairly regular (Li1,Sc)O6 octahedra which run parallel to [100], zigzag chains of edge-sharing, somewhat distorted, (Li2,Sc)O6 octahedra, which also run parallel to [100], and finally (Li3,Sc)O6 regular trigonal prisms which share prism edges to form zigzag chains, again parallel to [100]. These three (Li,Sc)O6 polyhedra share corners with two non-equivalent MoO4 tetrahedra. The latter show relatively small angular distortions (Table 1) and similar average Mo—O bond lengths of 1.769 (Mo1) and 1.772 Å (Mo2), respectively. In Li3Fe(MoO4)3 (Klevtsova & Magarill, 1970), the average Mo—O bond length is only slightly larger, 1.781 Å.
The topology of the structure type can also be described as close-packed sheets of O atoms, composed of three-square-wide bands of the No. 9 regular net of Wells (1952) held together by semi-regular single chains of triangles; regular and semi-regular voids between the O atoms are filled by the Li and MIII/MIIcations (see Ozima et al., 1977, for further details).
The fact that the trigonal–prismatic site in Li3Sc(MoO4)3, Li3, contains about 8% Sc seems to distinguish it from Li3Fe(MoO4)3, for which the equivalent site was reported to be occupied by Li only (Klevtsova & Magarill, 1970). Comparable minor discrepancies were noted for Li2Co2(MoO4)3 by Wiesmann et al. (1995) who stated that three positions for Co were determined for their compound instead of two as reported by Penkova & Klevtsov (1977); all three positions are partially occupied by Co and Li with different site occupations, with the highest Li:Co ratio being 0.79:0.21 on the trigonal-prismatic site, and the lowest Li:Co ratio being 0.34:0.66 on the edge-sharing octahedral site. Nonetheless, in Li2Ni2(MoO4)3, the trigonal-prismatic site was found to be occupied by Li only (Ozima et al., 1977), and in `NaCo2.31(MoO4)3' [= Na2CoII2(MoO4)3; Klevtsova & Magarill, 1970], the same site hosted Na only (Ibers & Smith, 1964). Although modern data collections and refinements might reveal small amounts of M cations on the trigonal-prismatic site in all these structures, the respective occupancies may all be dependent on temperature of formation or kinetic influences, availability of cations, and also possible oxidation of MII cations. The common framework structure type is relatively flexible in adapting to different Li:M ratios on the three different (Li/M) sites (Ozima et al., 1977).
By comparison with the isostructural Li3Fe(MoO4)3 (Klevtsova & Magarill, 1970), all unit-cell parameters of the Sc member are enlarged, and the cell volume is increased by 2.56%. This is expected from the average M—O bond lengths of six-coordinated Sc and FeIII (2.105 and 2.011 Å, respectively; Baur, 1981). The presently determined unit-cell parameters of the title compound are, except for the parameter a, slightly smaller than those refined earlier from X-ray powder diffraction data, a = 5.12 (10), b = 10.65 (7), c = 17.86 (5) Å and V = 974 Å3 (Klevtsov, 1970; note: s.u. values estimated from error bars given in Fig. 2 of Klevtsov's paper). Unit-cell parameters given for `LiSc(MoO4)2', a = 5.12 (1), b = 10.52 (2), c = 17.86 (2) Å and V = 962 Å3 (Porotnikov et al., 1982; ICDD-PDF 36–207), suggest that this compound is in fact more likely to be Li3Sc(MoO4)3.
Although Li3Al(MoO4)3 is known to exist (Klevtsov, 1970; Trunov & Efremov, 1971; Kozhevnikova et al., 1980), and the flux used for crystal growth contained dissolved AlIII ions, the chemical analyses showed that the crystals of the title compound contained no Al. Thus, Sc strongly partitions into Li3Sc(MoO4)3, whereas Al was completely used up by (earlier?) crystallization of the accompanying LiAl5O8 octahedra (see Experimental).