Aragonite-type lanthanum orthoborate, LaBO₃

The crystal structure of the low-temperature (LT) modification of LaBO₃ has been redetermined from single-crystal X-ray data; the resulting structure confirms the previous study [Abdullaev, Dzhafarov & Mamedov (1976). Azerbaidzhanskii Khim. Zh. pp. 117–120], but with improved precision. LT-LaBO₃ crystallizes in space group Pnma and adopts the aragonite-type structure. Except for one O atom, which is situated on a general position, all other atoms (one La, one B and a second O atom) lie on mirror planes. The structure is composed of LaO₉ polyhedra with an average La—O distance of 2.593 Å and trigonal BO₃ groups with an average B—O distance of 1.373 Å. Slight anisotropies of the thermal vibrations of La and B atoms suggest that the electrostatic La...La and La...B inter­actions across the shared edges are weak.

Key indicators

• Single-crystal X-ray study
• T = 296 K
• Mean [sigma](O-B)= 0.004 Å
• R factor = 0.017
• wR factor = 0.029
• Data-to-parameter ratio = 12.7

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Computing details

Data collection: WinAFC (Rigaku Corporation, 1999); cell refinement: WinAFC; data reduction: TEXSAN (Molecular Structure Corporation, 1999); program(s) used to solve structure: TEXSAN; program(s) used to refine structure: TEXSAN; molecular graphics: ATOMS (Dowty, 2000); software used to prepare material for publication: TEXSAN.

lanthanum orthoborate

Crystal data

LaBO3	F(000) = 344
Mr = 197.71	Dx = 5.299 Mg m^−3
Orthorhombic, Pnma	Mo Kα radiation, λ = 0.71069 Å
Hall symbol: -P 2ac 2n	Cell parameters from 50 reflections
a = 5.8744 (3) Å	θ = 22.5–25.0°
b = 5.1087 (3) Å	µ = 16.88 mm^−1
c = 8.2581 (5) Å	T = 296 K
V = 247.83 (2) Å^3	Irregular, colorless
Z = 4	0.06 × 0.05 × 0.04 mm

Data collection

Rigaku AFC-7R diffractometer	Rint = 0.030
ω–2θ scans	θmax = 30.0°
Absorption correction: part of the refinement model (ΔF) (Walker & Stuart, 1983)	h = −8→8
Tmin = 0.418, Tmax = 0.509	k = 0→7
1591 measured reflections	l = −11→11
396 independent reflections	3 standard reflections every 150 reflections
369 reflections with F^2 > 2σ(F^2)	intensity decay: 0.6%

Refinement

Refinement on F	w = 1/[σ^2(Fo) + 0.00014|Fo|^2]
R[F^2 > 2σ(F^2)] = 0.017	(Δ/σ)max = 0.001
wR(F^2) = 0.029	Δρmax = 1.24 e Å^−3
S = 1.98	Δρmin = −0.98 e Å^−3
369 reflections	Extinction correction: Zachariasen (1967) type 2 Gaussian isotropic
29 parameters	Extinction coefficient: 0.056 (3)

Special details

Refinement. Refinement using reflections with F² > 2.0 σ(F²). The weighted R-factor (wR), goodness of fit (S) and R-factor (gt) are based on F, with F set to zero for negative F. The threshold expression of F² > 2.0 σ(F²) is used only for calculating R-factor (gt).

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

	x	y	z	Uiso*/Ueq
La	0.24319 (3)	0.2500	0.58449 (3)	0.0062 (1)
B	0.5822 (7)	0.2500	0.2611 (5)	0.0079 (10)
O1	0.0970 (5)	0.2500	0.0729 (3)	0.0097 (7)
O2	0.5863 (4)	0.0182 (4)	0.1769 (2)	0.0092 (4)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
La	0.0062 (2)	0.0062 (2)	0.0063 (2)	0.0000	0.00038 (6)	0.0000
B	0.007 (2)	0.008 (2)	0.009 (2)	0.0000	0.000 (1)	0.0000
O1	0.011 (1)	0.012 (1)	0.006 (1)	0.0000	−0.002 (1)	0.0000
O2	0.0118 (9)	0.0064 (9)	0.0095 (9)	0.0000 (8)	0.0002 (7)	0.0008 (8)

Geometric parameters (Å, º)

La—O1^i	2.451 (3)	B—O2^i	3.230 (4)
La—O1^ii	2.723 (1)	B—O2^x	3.230 (4)
La—O1^iii	2.723 (1)	B—B^i	2.943 (6)
La—O2^ii	2.491 (2)	B—B^v	2.943 (6)
La—O2^iv	2.491 (2)	O1—O1^xiii	3.045 (3)
La—O2^v	2.629 (2)	O1—O1^xiv	3.045 (3)
La—O2^vi	2.629 (2)	O1—O2	3.225 (3)
La—O2^vii	2.601 (2)	O1—O2^xii	3.225 (3)
La—O2^viii	2.601 (2)	O1—O2^xv	3.338 (3)
La—B	3.331 (4)	O1—O2^xvi	3.338 (3)
La—B^ii	3.508 (3)	O1—O2^v	2.383 (3)
La—B^v	3.007 (4)	O1—O2^vi	2.383 (3)
La—B^iii	3.508 (3)	O1—O2^xvii	3.705 (3)
La—B^ix	3.034 (2)	O1—O2^xviii	3.705 (3)
La—B^vii	3.034 (2)	O1—O2^xix	3.097 (3)
B—O1^x	1.374 (5)	O1—O2^xx	3.097 (3)
B—O1	3.247 (5)	O2—O2^xii	2.368 (4)
B—O1^xi	3.400 (5)	O2—O2^x	3.176 (2)
B—O2	1.373 (3)	O2—O2^vi	3.176 (2)
B—O2^xii	1.373 (3)	O2—O2^xxi	2.740 (4)
B—O2^v	3.186 (5)	O2—O2^xx	3.098 (4)
B—O2^vi	3.186 (5)
O1^i—La—O1^ii	71.88 (6)	La^v—O1—La^xvii	108.12 (6)
O1^i—La—O1^iii	71.88 (6)	La^v—O1—La^xxii	108.12 (6)
O1^i—La—O2^ii	145.20 (5)	La^v—O1—O2^v	115.9 (1)
O1^i—La—O2^iv	145.20 (5)	La^v—O1—O2^vi	115.9 (1)
O1^i—La—O2^v	82.06 (8)	La^v—O1—B^v	118.4 (2)
O1^i—La—O2^vi	82.06 (8)	La^xvii—O1—La^xxii	139.4 (1)
O1^i—La—O2^vii	94.31 (7)	La^xvii—O1—O2^v	116.4 (1)
O1^i—La—O2^viii	94.31 (7)	La^xvii—O1—O2^vi	60.81 (5)
O1^ii—La—O1^iii	139.4 (1)	La^xvii—O1—B^v	89.23 (10)
O1^ii—La—O2^ii	76.28 (7)	La^xxii—O1—O2^v	60.81 (5)
O1^ii—La—O2^iv	142.61 (7)	La^xxii—O1—O2^vi	116.4 (1)
O1^ii—La—O2^v	120.96 (7)	La^xxii—O1—B^v	89.23 (10)
O1^ii—La—O2^vi	70.69 (7)	O2^v—O1—O2^vi	59.6 (1)
O1^ii—La—O2^vii	112.84 (7)	La^i—O2—La^xvii	105.58 (7)
O1^ii—La—O2^viii	53.11 (7)	La^i—O2—La^ix	136.43 (9)
O1^iii—La—O2^ii	142.61 (7)	La^i—O2—O1^i	118.62 (9)
O1^iii—La—O2^iv	76.28 (7)	La^i—O2—O2^xii	63.23 (4)
O1^iii—La—O2^v	70.69 (7)	La^i—O2—O2^xxi	116.77 (4)
O1^iii—La—O2^vi	120.96 (7)	La^i—O2—B	91.9 (2)
O1^iii—La—O2^vii	53.11 (7)	La^xvii—O2—La^ix	103.98 (7)
O1^iii—La—O2^viii	112.84 (7)	La^xvii—O2—O1^i	124.0 (1)
O2^ii—La—O2^iv	66.73 (9)	La^xvii—O2—O2^xii	123.37 (5)
O2^ii—La—O2^v	103.11 (4)	La^xvii—O2—O2^xxi	56.63 (5)
O2^ii—La—O2^vi	74.42 (7)	La^xvii—O2—B	128.0 (2)
O2^ii—La—O2^vii	110.91 (5)	La^ix—O2—O1^i	66.08 (6)
O2^ii—La—O2^viii	77.14 (5)	La^ix—O2—O2^xii	121.79 (4)
O2^iv—La—O2^v	74.42 (7)	La^ix—O2—O2^xxi	58.21 (4)
O2^iv—La—O2^vi	103.11 (4)	La^ix—O2—B	94.4 (2)
O2^iv—La—O2^vii	77.14 (5)	O1^i—O2—O2^xii	60.20 (6)
O2^iv—La—O2^viii	110.91 (5)	O1^i—O2—O2^xxi	119.80 (6)
O2^v—La—O2^vi	53.55 (9)	O2^xii—O2—O2^xxi	180.0
O2^v—La—O2^vii	121.32 (2)	O2^xxi—O2—B	149.6 (2)
O2^v—La—O2^viii	173.98 (8)	O1^i—B—O2	120.3 (2)
O2^vi—La—O2^vii	173.98 (8)	O1^i—B—O2^xii	120.3 (2)
O2^vi—La—O2^viii	121.32 (2)	O2—B—O2^xii	119.1 (3)
O2^vii—La—O2^viii	63.59 (9)

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