A mixed-valent niobium oxy­sulfide, La₂Nb₃S₂O₈

Dilanthanum triniobium di­sulfide octaoxide, La₂Nb₃S₂O₈, crystallizes in the orthorhombic space group Pnnm and is isostructural with the Ln₂Ta₃X₂O₈ (Ln = La, Ce, Pr and Nd, and X = S and Se) family of tantalum compounds. Nb⁴⁺ and Nb⁵⁺ ions co-exist in the structure and occupy different crystallographic sites. While the Nb⁴⁺ ions are found in mixed oxy­gen and sulfur octahedra, the Nb⁵⁺ ions are found in oxy­gen-only octahedra.

S1. Comment

Oxychalcogenides containing electropositive elements, like rare earth or alkaline earth metals, combined with transition metals often exhibit a lamellar structure, with a segregation in the oxide and sulfide layers. The Ln₂Ti₂S₂O₅ (Ln = La, Ce, Sm and Pr) family of compounds (Boyer, 1999; Goga, 1999) is a good example of such intergrowth structures, with [Ln₂S₂] rock-salt-type layers alternating regularly with [Ti₂O₅] perovskite-type layers. The structure of the (Sr_n+1M_nO_3n-1)(Cu₂S₂) (M = Sc, Fe, Ni and Cu) family of compounds (Zhu, 1997; Otzschi, 1999) can also be described as an intergrowth of perovskite- and fluorite-type layers. Recently, a niobium oxysulfide, namely La_10.8Nb₅S₁₀O₂₀, was reported to have an intergrowth structure in which [Ln₂S₂] rock-salt-type layers alternate with a complex mixed lanthanum and niobium oxysulfide layer (Boyer-Candalen, 2000). In a quest for a much simpler intergrowth structure in the La/Nb/S/O system, we have found the title compound, La₂Nb₃S₂O₈, as a by-product. A black needle-shaped crystal was mounted on a Nonius CCD diffractometer for data collection. The observed systematic conditions (k+l = 2n for 0kl and h + l= 2n for h0l) led to only two possible space groups, viz. Pnn2 (No. 34) and Pnnm (No. 58), and the intensity statistics indicated a centrosymmetric space group. Subsequently, we realised that La₂Nb₃S₂O₈ was isostructural with the Ln₂Ta₃X₂O₈ (Ln = La, Ce, Pr and Nd, and X = S and Se) family of tantalum compounds (Brennan, 1991; Brennan, 1992). Using the reported atomic parameters and space group Pnnm, the refinement led to a reliability factor, R, of 2.58% for the observed reflections and 80 parameters. At this stage, examination of the Fourier difference map revealed a residual peak (+4.52 e⁻.Å⁻³) of Nb1 at 0.63 Å. We then refined atom Nb11 on this site, constraining the sum of the site-occupancy factors of atoms Nb1 and Nb11 to be constant and the atomic displacement parameters of the two atoms to be identical. The refinement led to a better reliability factor (R=2.47%) for the observed reflections and 81 parameters. The atomic coordinates and isotropic or equivalent atomic displacement parameters corresponding to this last refinement are listed in Table 1. The projection of the structure of La₂Nb₃S₂O₈ is shown Fig. 1. La atoms are located in tricapped-trigonal prismatic sites consisting of seven O and two S atoms. Atoms Nb2 are located in distorted octahedral environments consisting only of O atoms, while atoms Nb1 and Nb11 are located in a distorted octahedral environment containing mixed anions (two O and four S atoms). As shown in Fig. 2, atoms Nb1 are shifted from the center of the octahedra along the c axis. Consequently, two consecutive Nb1 atoms form, along this direction, either a short contact [3.368 (2) Å] or an elongated contact [4.301 (2) Å]. Atoms Nb11 behave in a similar manner, but these atoms are shifted along the c axis in the opposite direction to atom Nb1 (Fig. 2). We observed a superstructure that led to the doubling of the c parameter from 3.83 Å to 7.66 Å. In the structure, the doubling of the c axis is only a result of the displacement of atoms Nb1 or Nb11 from the center of the surrounding octahedron. Atoms Nb1 and Nb11 displaced along the c direction in opposite directions from the center of the octahedron by c/2. Therefore, we believe that the Nb11-atom position corresponds to stacking faults. The shortest Nb1···Nb1 distance (3.368 Å) is comparable to the Nb2···Nb2 distance (3.328 Å) and is longer than the distance expected for a Peierls-like pair (around 3 Å). Using the bond-valence method (Brown, 1981; Brese, 1991) and the refined Nb—O and Nb—S distances, we found bond-valence sums of 4.04 and 5.01 for atoms Nb1 and Nb2, respectively. These values are in excellent agreement with the charge equilibrium, (La⁺³)₂(Nb⁺⁴)₁(Nb⁺⁵)₂(S⁻²)₂(O⁻²)₈, and clearly attest that La₂Nb₃S₂O₈ is a mixed-valent compound with Nb⁺⁴ and Nb⁺⁵ ions in distinct crystallographic sites.

S2. Experimental

La₂Nb₃S₂O₈ was obtained as a by-product during an exploration of the La—Nb—S—O system. Powdered La₂S₃, Nb₂O₅ and La₂O₃, weighted in a ratio of 4:3:2, were finely mixed and pressed into a pellet. The pellet was sealed in an evacuated silica tube and heated at 1273 K for 120 h. The intermediate reaction product was ground, mixed with a small amount of iodine to favor crystallization, and reheated in a temperature gradient furnace at 1273 K for 240 h. Small black needle-shaped crystals of the title compound were found at the cool end of the tube. Chemical analyses performed on these crystals using an EDS-equipped scanning electron microscope revealed an La/Nb/S ratio close to 2:3:2.

Computing details

Data collection: Collect (Nonius BV, 1997–2000); cell refinement: HKL SCALEPACK (Otwinowski & Minor 1997); data reduction: HKL DENZO and SCALEPACK (Otwinowski & Minor 1997); program(s) used to solve structure: not used (isotypic); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: Diamond (Brandenburg, 2001); software used to prepare material for publication: SHELXTL (Bruker, 1998).

Figures

	Fig. 1. A view of the structure of La2Nb3S2O8 along the c axis. Displacement ellipsoids are shown at the 80% probability level.
	Fig. 2. A view of the Nb1- or Nb11-atom chain running along the c axis. Displacement ellipsoids are shown at the 80% probability level.

(I)

Crystal data

La2Nb3S2O8	Dx = 5.571 Mg m^−3
Mr = 748.67	Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, Pnnm	Cell parameters from 12094 reflections
a = 9.8698 (2) Å	θ = 2.9–35.0°
b = 11.7941 (3) Å	µ = 13.58 mm^−1
c = 7.6686 (1) Å	T = 293 K
V = 892.7 (2) Å^3	Needle, black
Z = 4	0.07 × 0.03 × 0.03 mm
F(000) = 1332

Data collection

Nonius KappaCCD diffractometer	2070 independent reflections
Radiation source: fine-focus sealed tube	1811 reflections with I > 2σ(I)
Horizonally mounted graphite crystal monochromator	Rint = 0.064
Detector resolution: 9 pixels mm^-1	θmax = 35.0°, θmin = 3.2°
CCD scans	h = −15→15
Absorption correction: gaussian (Jana2000; Petricek and Dusek, 2000)	k = −18→19
Tmin = 0.511, Tmax = 0.747	l = −12→12
20315 measured reflections

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	w = 1/[σ^2(Fo^2) + (0.0145P)^2 + 3.1635P] where P = (Fo^2 + 2Fc^2)/3
R[F^2 > 2σ(F^2)] = 0.025	(Δ/σ)max = 0.001
wR(F^2) = 0.052	Δρmax = 1.38 e Å^−3
S = 1.08	Δρmin = −1.38 e Å^−3
2070 reflections	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
81 parameters	Extinction coefficient: 0.00085 (8)
0 restraints

Special details

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
La1	0.20706 (2)	0.33944 (2)	0.0000	0.00785 (6)
La2	0.22535 (2)	0.34680 (2)	−0.5000	0.00781 (6)
Nb1	0.0000	0.0000	0.2804 (2)	0.01026 (19)	0.951 (7)
Nb11	0.0000	0.0000	0.222 (4)	0.01026 (19)	0.049 (7)
Nb2	0.13612 (2)	0.58326 (2)	−0.25019 (3)	0.00590 (7)
S1	0.01977 (11)	0.13626 (10)	0.0000	0.01103 (19)
S2	0.51757 (11)	0.34708 (9)	0.0000	0.01086 (19)
O1	0.2864 (2)	0.2231 (2)	−0.2507 (3)	0.0098 (4)
O2	0.1348 (3)	0.5537 (3)	0.0000	0.0096 (5)
O3	0.3026 (2)	0.4744 (2)	0.2377 (3)	0.0081 (4)
O4	−0.0552 (2)	0.6044 (2)	−0.2551 (2)	0.0084 (4)
O5	0.1487 (3)	0.5510 (3)	−0.5000	0.0088 (5)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
La1	0.00918 (10)	0.00841 (11)	0.00597 (11)	0.00073 (8)	0.000	0.000
La2	0.00894 (10)	0.00833 (11)	0.00615 (11)	0.00096 (8)	0.000	0.000
Nb1	0.00571 (16)	0.01073 (19)	0.0143 (6)	0.00048 (13)	0.000	0.000
Nb11	0.00571 (16)	0.01073 (19)	0.0143 (6)	0.00048 (13)	0.000	0.000
Nb2	0.00596 (11)	0.00642 (12)	0.00531 (13)	−0.00045 (8)	−0.00005 (8)	−0.00007 (8)
S1	0.0086 (4)	0.0118 (5)	0.0128 (5)	−0.0016 (3)	0.000	0.000
S2	0.0090 (4)	0.0111 (5)	0.0125 (5)	0.0015 (3)	0.000	0.000
O1	0.0112 (10)	0.0081 (10)	0.0102 (10)	0.0029 (7)	−0.0002 (7)	−0.0002 (7)
O2	0.0111 (13)	0.0120 (14)	0.0056 (13)	0.0005 (11)	0.000	0.000
O3	0.0066 (9)	0.0094 (10)	0.0082 (10)	0.0008 (7)	−0.0001 (7)	0.0002 (7)
O4	0.0061 (8)	0.0107 (10)	0.0083 (10)	0.0001 (7)	0.0003 (7)	0.0001 (7)
O5	0.0116 (13)	0.0094 (13)	0.0055 (13)	−0.0009 (11)	0.000	0.000

Geometric parameters (Å, º)

La1—O1	2.488 (2)	Nb11—S1^xii	2.35 (2)
La1—O1^i	2.488 (2)	Nb11—S1	2.35 (2)
La1—O4^ii	2.552 (2)	Nb11—S2^xi	2.80 (2)
La1—O4^iii	2.552 (2)	Nb11—S2^ix	2.80 (2)
La1—O3	2.597 (2)	Nb11—La2^xiii	3.675 (13)
La1—O3^i	2.597 (2)	Nb11—La2^xi	3.675 (13)
La1—O2	2.625 (3)	Nb2—O1^xiv	1.818 (2)
La1—S1	3.0265 (12)	Nb2—O4	1.905 (2)
La1—S2	3.0659 (11)	Nb2—O2	1.9501 (6)
La1—Nb2^i	3.5271 (7)	Nb2—O5	1.9570 (7)
La1—Nb2	3.5271 (7)	Nb2—O3^i	2.088 (2)
La2—O1	2.479 (2)	Nb2—O4^ii	2.353 (2)
La2—O1^iv	2.479 (2)	Nb2—Nb2^ii	3.3282 (6)
La2—O5	2.524 (3)	S1—Nb11^xii	2.35 (2)
La2—O4^v	2.585 (2)	S1—Nb1^xii	2.6918 (16)
La2—O4^ii	2.585 (2)	S1—La2^xi	2.9127 (11)
La2—O3^i	2.626 (2)	S2—Nb1^xv	2.4734 (15)
La2—O3^vi	2.626 (2)	S2—Nb1^vii	2.4734 (15)
La2—S1^vii	2.9127 (11)	S2—Nb11^xv	2.80 (2)
La2—S2^viii	3.0716 (12)	S2—Nb11^vii	2.80 (2)
La2—Nb2^iv	3.4960 (6)	S2—La2^xvi	3.0716 (12)
La2—Nb2	3.4961 (6)	O1—Nb2^xiii	1.818 (2)
La2—Nb11^vii	3.675 (13)	O2—Nb2^i	1.9502 (6)
Nb1—O3^ix	1.976 (2)	O3—Nb1^xv	1.976 (2)
Nb1—O3^x	1.976 (2)	O3—Nb11^xv	1.996 (5)
Nb1—S2^xi	2.4734 (15)	O3—Nb2^i	2.088 (2)
Nb1—S2^ix	2.4734 (15)	O3—La2^xvii	2.626 (2)
Nb1—S1^xii	2.6917 (16)	O4—Nb2^ii	2.353 (2)
Nb1—S1	2.6918 (16)	O4—La1^iii	2.552 (2)
Nb11—O3^ix	1.996 (5)	O4—La2^v	2.585 (2)
Nb11—O3^x	1.996 (5)	O5—Nb2^iv	1.9570 (7)
O1—La1—O1^i	101.19 (10)	O3^ix—Nb1—S2^xi	95.17 (8)
O1—La1—O4^ii	74.68 (7)	O3^x—Nb1—S2^xi	90.32 (8)
O1^i—La1—O4^ii	156.96 (8)	O3^ix—Nb1—S2^ix	90.32 (8)
O1—La1—O4^iii	156.96 (8)	O3^x—Nb1—S2^ix	95.17 (8)
O1^i—La1—O4^iii	74.68 (7)	S2^xi—Nb1—S2^ix	94.20 (7)
O4^ii—La1—O4^iii	100.07 (9)	O3^ix—Nb1—S1^xii	85.65 (8)
O1—La1—O3	139.98 (7)	O3^x—Nb1—S1^xii	87.91 (8)
O1^i—La1—O3	71.42 (8)	S2^xi—Nb1—S1^xii	169.83 (6)
O4^ii—La1—O3	126.31 (7)	S2^ix—Nb1—S1^xii	95.94 (3)
O4^iii—La1—O3	61.08 (7)	O3^ix—Nb1—S1	87.91 (8)
O1—La1—O3^i	71.42 (8)	O3^x—Nb1—S1	85.65 (8)
O1^i—La1—O3^i	139.98 (7)	S2^xi—Nb1—S1	95.94 (3)
O4^ii—La1—O3^i	61.08 (7)	S2^ix—Nb1—S1	169.83 (6)
O4^iii—La1—O3^i	126.31 (7)	S1^xii—Nb1—S1	73.94 (6)
O3—La1—O3^i	89.14 (9)	O3^ix—Nb11—O3^x	162.1 (16)
O1—La1—O2	128.03 (5)	O3^ix—Nb11—S1^xii	95.2 (5)
O1^i—La1—O2	128.03 (5)	O3^x—Nb11—S1^xii	97.8 (5)
O4^ii—La1—O2	65.83 (6)	O3^ix—Nb11—S1	97.8 (5)
O4^iii—La1—O2	65.83 (6)	O3^x—Nb11—S1	95.2 (5)
O3—La1—O2	60.58 (6)	S1^xii—Nb11—S1	87.2 (10)
O3^i—La1—O2	60.58 (6)	O3^ix—Nb11—S2^xi	85.3 (7)
O1—La1—S1	75.86 (6)	O3^x—Nb11—S2^xi	81.0 (6)
O1^i—La1—S1	75.86 (6)	S1^xii—Nb11—S2^xi	176.6 (8)
O4^ii—La1—S1	81.18 (5)	S1—Nb11—S2^xi	96.09 (11)
O4^iii—La1—S1	81.18 (5)	O3^ix—Nb11—S2^ix	81.0 (6)
O3—La1—S1	135.00 (5)	O3^x—Nb11—S2^ix	85.3 (7)
O3^i—La1—S1	135.00 (5)	S1^xii—Nb11—S2^ix	96.09 (11)
O2—La1—S1	126.58 (7)	S1—Nb11—S2^ix	176.6 (8)
O1—La1—S2	72.64 (5)	S2^xi—Nb11—S2^ix	80.7 (8)
O1^i—La1—S2	72.64 (5)	O3^ix—Nb11—La2^xiii	43.8 (4)
O4^ii—La1—S2	125.42 (5)	O3^x—Nb11—La2^xiii	150.0 (8)
O4^iii—La1—S2	125.42 (5)	S1^xii—Nb11—La2^xiii	52.4 (3)
O3—La1—S2	67.60 (5)	S1—Nb11—La2^xiii	86.6 (6)
O3^i—La1—S2	67.60 (5)	S2^xi—Nb11—La2^xiii	128.6 (3)
O2—La1—S2	104.08 (7)	S2^ix—Nb11—La2^xiii	94.69 (9)
S1—La1—S2	129.33 (3)	O3^ix—Nb11—La2^xi	150.0 (8)
O1—La1—Nb2^i	158.79 (5)	O3^x—Nb11—La2^xi	43.8 (4)
O1^i—La1—Nb2^i	95.26 (5)	S1^xii—Nb11—La2^xi	86.6 (6)
O4^ii—La1—Nb2^i	95.09 (5)	S1—Nb11—La2^xi	52.4 (3)
O4^iii—La1—Nb2^i	41.83 (5)	S2^xi—Nb11—La2^xi	94.69 (9)
O3—La1—Nb2^i	35.97 (5)	S2^ix—Nb11—La2^xi	128.6 (3)
O3^i—La1—Nb2^i	87.37 (5)	La2^xiii—Nb11—La2^xi	124.9 (8)
O2—La1—Nb2^i	33.013 (8)	O1^xiv—Nb2—O4	107.34 (10)
S1—La1—Nb2^i	121.62 (2)	O1^xiv—Nb2—O2	99.29 (12)
S2—La1—Nb2^i	100.046 (19)	O4—Nb2—O2	92.06 (11)
O1—La1—Nb2	95.26 (5)	O1^xiv—Nb2—O5	98.83 (11)
O1^i—La1—Nb2	158.79 (5)	O4—Nb2—O5	93.96 (11)
O4^ii—La1—Nb2	41.83 (5)	O2—Nb2—O5	158.23 (15)
O4^iii—La1—Nb2	95.09 (5)	O1^xiv—Nb2—O3^i	103.11 (10)
O3—La1—Nb2	87.37 (5)	O4—Nb2—O3^i	149.51 (9)
O3^i—La1—Nb2	35.97 (5)	O2—Nb2—O3^i	81.38 (11)
O2—La1—Nb2	33.012 (8)	O5—Nb2—O3^i	82.85 (10)
S1—La1—Nb2	121.62 (2)	O1^xiv—Nb2—O4^ii	174.94 (9)
S2—La1—Nb2	100.047 (19)	O4—Nb2—O4^ii	77.66 (10)
Nb2^i—La1—Nb2	65.908 (16)	O2—Nb2—O4^ii	81.08 (11)
O1—La1—La2	39.29 (5)	O5—Nb2—O4^ii	79.82 (10)
O1^i—La1—La2	140.29 (5)	O3^i—Nb2—O4^ii	71.92 (8)
O4^ii—La1—La2	41.95 (5)	O1^xiv—Nb2—Nb2^ii	151.03 (7)
O4^iii—La1—La2	141.92 (5)	O4—Nb2—Nb2^ii	43.70 (7)
O3—La1—La2	132.06 (5)	O2—Nb2—Nb2^ii	83.62 (9)
O3^i—La1—La2	42.97 (5)	O5—Nb2—Nb2^ii	86.36 (9)
O2—La1—La2	89.484 (6)	O3^i—Nb2—Nb2^ii	105.82 (6)
S1—La1—La2	92.672 (5)	O4^ii—Nb2—Nb2^ii	34.00 (5)
S2—La1—La2	87.270 (5)	O1^xiv—Nb2—La2	128.31 (7)
Nb2^i—La1—La2	122.284 (10)	O4—Nb2—La2	110.09 (7)
Nb2—La1—La2	56.473 (8)	O2—Nb2—La2	113.45 (10)
O1—La2—O1^iv	100.91 (10)	O5—Nb2—La2	44.98 (9)
O1—La2—O5	129.36 (5)	O3^i—Nb2—La2	48.42 (6)
O1^iv—La2—O5	129.37 (5)	O4^ii—Nb2—La2	47.67 (5)
O1—La2—O4^v	148.15 (7)	Nb2^ii—Nb2—La2	74.495 (13)
O1^iv—La2—O4^v	74.25 (7)	O1^xiv—Nb2—La1	130.85 (7)
O5—La2—O4^v	65.97 (7)	O4—Nb2—La1	108.31 (7)
O1—La2—O4^ii	74.25 (7)	O2—Nb2—La1	47.18 (10)
O1^iv—La2—O4^ii	148.15 (7)	O5—Nb2—La1	111.19 (9)
O5—La2—O4^ii	65.97 (7)	O3^i—Nb2—La1	46.95 (6)
O4^v—La2—O4^ii	93.22 (9)	O4^ii—Nb2—La1	46.31 (5)
O1—La2—O3^i	71.08 (8)	Nb2^ii—Nb2—La1	71.289 (13)
O1^iv—La2—O3^i	149.04 (7)	La2—Nb2—La1	66.279 (13)
O5—La2—O3^i	62.63 (6)	Nb11^xii—S1—Nb11	92.8 (10)
O4^v—La2—O3^i	128.17 (7)	Nb11^xii—S1—Nb1	99.4 (5)
O4^ii—La2—O3^i	60.29 (7)	Nb11—S1—Nb1	6.6 (5)
O1—La2—O3^vi	149.04 (7)	Nb11^xii—S1—Nb1^xii	6.6 (5)
O1^iv—La2—O3^vi	71.08 (8)	Nb11—S1—Nb1^xii	99.4 (5)
O5—La2—O3^vi	62.63 (6)	Nb1—S1—Nb1^xii	106.06 (6)
O4^v—La2—O3^vi	60.29 (7)	Nb11^xii—S1—La2^xi	87.94 (3)
O4^ii—La2—O3^vi	128.17 (7)	Nb11—S1—La2^xi	87.94 (3)
O3^i—La2—O3^vi	100.03 (9)	Nb1—S1—La2^xi	88.20 (3)
O1—La2—S1^vii	78.33 (5)	Nb1^xii—S1—La2^xi	88.20 (3)
O1^iv—La2—S1^vii	78.33 (5)	Nb11^xii—S1—La1	126.3 (4)
O5—La2—S1^vii	103.51 (7)	Nb11—S1—La1	126.3 (4)
O4^v—La2—S1^vii	129.28 (5)	Nb1—S1—La1	121.13 (3)
O4^ii—La2—S1^vii	129.28 (5)	Nb1^xii—S1—La1	121.13 (3)
O3^i—La2—S1^vii	70.78 (5)	La2^xi—S1—La1	123.71 (4)
O3^vi—La2—S1^vii	70.78 (5)	Nb1^xv—S2—Nb1^vii	85.80 (7)
O1—La2—S2^viii	73.99 (6)	Nb1^xv—S2—Nb11^xv	6.8 (3)
O1^iv—La2—S2^viii	73.99 (6)	Nb1^vii—S2—Nb11^xv	92.6 (4)
O5—La2—S2^viii	120.68 (7)	Nb1^xv—S2—Nb11^vii	92.6 (4)
O4^v—La2—S2^viii	74.45 (5)	Nb1^vii—S2—Nb11^vii	6.8 (3)
O4^ii—La2—S2^viii	74.45 (5)	Nb11^xv—S2—Nb11^vii	99.3 (8)
O3^i—La2—S2^viii	128.36 (5)	Nb1^xv—S2—La1	87.21 (3)
O3^vi—La2—S2^viii	128.36 (5)	Nb1^vii—S2—La1	87.21 (3)
S1^vii—La2—S2^viii	135.82 (3)	Nb11^xv—S2—La1	87.54 (3)
O1—La2—Nb2^iv	162.40 (5)	Nb11^vii—S2—La1	87.54 (3)
O1^iv—La2—Nb2^iv	96.21 (5)	Nb1^xv—S2—La2^xvi	126.13 (4)
O5—La2—Nb2^iv	33.227 (8)	Nb1^vii—S2—La2^xvi	126.13 (4)
O4^v—La2—Nb2^iv	42.31 (5)	Nb11^xv—S2—La2^xvi	121.4 (3)
O4^ii—La2—Nb2^iv	93.26 (5)	Nb11^vii—S2—La2^xvi	121.4 (3)
O3^i—La2—Nb2^iv	92.05 (5)	La1—S2—La2^xvi	130.20 (4)
O3^vi—La2—Nb2^iv	36.50 (5)	Nb2^xiii—O1—La2	129.73 (10)
S1^vii—La2—Nb2^iv	101.34 (2)	Nb2^xiii—O1—La1	129.01 (10)
S2^viii—La2—Nb2^iv	115.19 (2)	La2—O1—La1	101.24 (8)
O1—La2—Nb2	96.21 (5)	Nb2—O2—Nb2^i	159.36 (19)
O1^iv—La2—Nb2	162.40 (5)	Nb2—O2—La1	99.81 (10)
O5—La2—Nb2	33.227 (7)	Nb2^i—O2—La1	99.81 (10)
O4^v—La2—Nb2	93.26 (5)	Nb1^xv—O3—Nb11^xv	13.0 (8)
O4^ii—La2—Nb2	42.31 (5)	Nb1^xv—O3—Nb2^i	133.26 (12)
O3^i—La2—Nb2	36.50 (5)	Nb11^xv—O3—Nb2^i	131.9 (2)
O3^vi—La2—Nb2	92.05 (5)	Nb1^xv—O3—La1	113.72 (10)
S1^vii—La2—Nb2	101.34 (2)	Nb11^xv—O3—La1	123.8 (6)
S2^viii—La2—Nb2	115.19 (2)	Nb2^i—O3—La1	97.09 (8)
Nb2^iv—La2—Nb2	66.454 (15)	Nb1^xv—O3—La2^xvii	115.32 (10)
O1—La2—Nb11^vii	75.7 (3)	Nb11^xv—O3—La2^xvii	104.5 (7)
O1^iv—La2—Nb11^vii	117.8 (3)	Nb2^i—O3—La2^xvii	95.08 (8)
O5—La2—Nb11^vii	75.64 (8)	La1—O3—La2^xvii	94.64 (7)
O4^v—La2—Nb11^vii	134.9 (3)	Nb2—O4—Nb2^ii	102.30 (10)
O4^ii—La2—Nb11^vii	91.9 (3)	Nb2—O4—La1^iii	126.96 (9)
O3^i—La2—Nb11^vii	31.7 (3)	Nb2^ii—O4—La1^iii	91.86 (7)
O3^vi—La2—Nb11^vii	81.9 (4)	Nb2—O4—La2^v	133.44 (9)
S1^vii—La2—Nb11^vii	39.7 (2)	Nb2^ii—O4—La2^v	90.01 (7)
S2^viii—La2—Nb11^vii	149.1 (3)	La1^iii—O4—La2^v	96.74 (7)
Nb2^iv—La2—Nb11^vii	92.7 (2)	Nb2^iv—O5—Nb2	156.41 (18)
Nb2—La2—Nb11^vii	62.61 (17)	Nb2^iv—O5—La2	101.79 (9)
O3^ix—Nb1—O3^x	171.94 (15)	Nb2—O5—La2	101.79 (9)

Symmetry codes: (i) x, y, −z; (ii) −x, −y+1, z; (iii) −x, −y+1, −z; (iv) x, y, −z−1; (v) −x, −y+1, −z−1; (vi) x, y, z−1; (vii) x+1/2, −y+1/2, z−1/2; (viii) x−1/2, −y+1/2, z−1/2; (ix) −x+1/2, y−1/2, −z+1/2; (x) x−1/2, −y+1/2, −z+1/2; (xi) x−1/2, −y+1/2, z+1/2; (xii) −x, −y, −z; (xiii) −x+1/2, y−1/2, −z−1/2; (xiv) −x+1/2, y+1/2, −z−1/2; (xv) −x+1/2, y+1/2, −z+1/2; (xvi) x+1/2, −y+1/2, z+1/2; (xvii) x, y, z+1.