Cubic phase of single-crystal LaAlO₃ perovskite synthesized at 4.5 GPa and 1273 K

Single crystals of LaAlO₃ (lanthanum aluminium trioxide) have been synthesized at 4.5 GPa and 1273 K, in the presence of an NaCl + KCl flux. The compound crystallizes with the cubic perovskite structure (space group Pm). The thermal vibration of the O atom is remarkably suppressed in the directions of the Al-O bonds, and this anisotropy ranks among the largest observed in stoichiometric cubic perovskites.

Key indicators

• Single-crystal X-ray study
• T = 296 K
• Mean [sigma](l-O)= 0.000 Å
• R factor = 0.008
• wR factor = 0.010
• Data-to-parameter ratio = 19.3

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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 for Windows (Dowty, 2000); software used to prepare material for publication: TEXSAN.

lanthanum aluminium trioxide

Crystal data

LaAlO3	Dx = 6.517 Mg m^−3
Mr = 213.89	Mo Kα radiation, λ = 0.71069 Å
Cubic, Pm3m	Cell parameters from 25 reflections
Hall symbol: -P 4 2 3	θ = 20.5–22.0°
a = 3.7913 (2) Å	µ = 19.60 mm^−1
V = 54.50 (1) Å^3	T = 296 K
Z = 1	Irregular, colorless
F(000) = 94	0.05 × 0.05 × 0.05 mm

Data collection

Rigaku AFC-7R diffractometer	Rint = 0.015
ω/2θ scans	θmax = 60.0°
Absorption correction: ψ scan (North et al., 1968)	h = 0→9
Tmin = 0.395, Tmax = 0.414	k = 0→9
521 measured reflections	l = 0→9
116 independent reflections	3 standard reflections every 150 reflections
116 reflections with F^2 > 3σ(F^2)	intensity decay: 0.4%

Refinement

Refinement on F	w = 1/[σ^2(Fo) + 0.00008|Fo|^2]
R[F^2 > 2σ(F^2)] = 0.008	(Δ/σ)max < 0.001
wR(F^2) = 0.010	Δρmax = 0.84 e Å^−3
S = 1.07	Δρmin = −0.64 e Å^−3
116 reflections	Extinction correction: Zachariasen (1967), type 2 Gaussian isotropic
6 parameters	Extinction coefficient: 0.34 (2)

Special details

Refinement. Refinement using reflections with F² > 3.0 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 > 3.0 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	0.0000	0.0000	0.0000	0.004299 (6)
Al	0.5000	0.5000	0.5000	0.00377 (2)
O	0.0000	0.5000	0.5000	0.0140 (1)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
La	0.00430 (4)	0.0043	0.0043	0.0000	0.0000	0.0000
Al	0.0038 (1)	0.0038	0.0038	0.0000	0.0000	0.0000
O	0.0027 (3)	0.0197 (4)	0.0197	0.0000	0.0000	0.0000

Geometric parameters (Å, º)

La—O	2.6809 (1)	Al—O^i	1.8957 (1)
La—O^i	2.6809 (1)	Al—O^ii	1.8957 (1)
La—O^ii	2.6809 (1)	Al—O^xii	1.8957 (1)
La—O^iii	2.6809 (1)	Al—O^xiii	1.8957 (1)
La—O^iv	2.6809 (1)	Al—O^xiv	1.8957 (1)
La—O^v	2.6809 (1)	O—O^i	2.6809 (1)
La—O^vi	2.6809 (1)	O—O^ii	2.6809 (1)
La—O^vii	2.6809 (1)	O—O^v	2.6809 (1)
La—O^viii	2.6809 (1)	O—O^vi	2.6809 (1)
La—O^ix	2.6809 (1)	O—O^xv	2.6809 (1)
La—O^x	2.6809 (1)	O—O^xvi	2.6809 (1)
La—O^xi	2.6809 (1)	O—O^xii	2.6809 (1)
Al—O	1.8957 (1)	O—O^xiii	2.6809 (1)
O—La—O^i	60.00	La—O—O^vi	60.00
O—La—O^ii	60.00	La—O—O^xv	120.00
O—La—O^iii	120.00	La—O—O^xvi	120.00
O—La—O^iv	120.00	La—O—O^xii	120.00
O—La—O^v	60.00	La—O—O^xiii	120.00
O—La—O^vi	60.00	Al—O—Al^xx	180.00
O—La—O^vii	180.00	Al—O—O^i	45.00
O—La—O^viii	90.00	Al—O—O^ii	45.00
O—La—O^ix	120.00	Al—O—O^v	135.00
O—La—O^x	90.00	Al—O—O^vi	135.00
O—La—O^xi	120.00	Al—O—O^xv	135.00
O—La^i—O^ii	60.00	Al—O—O^xvi	135.00
O—La^i—O^iii	120.00	Al—O—O^xii	45.00
O—La^ii—O^iv	120.00	Al—O—O^xiii	45.00
O—Al—O^i	90.00	Al—O^xx—O^v	45.00
O—Al—O^ii	90.00	Al—O^xx—O^vi	45.00
O—Al—O^xii	90.00	Al—O^xx—O^xv	45.00
O—Al—O^xiii	90.00	Al—O^xx—O^xvi	45.00
O—Al—O^xiv	180.00	O—O^i—O^ii	60.00
O—Al^i—O^ii	90.00	O—O^i—O^xvi	180.00
O—Al^i—O^xii	90.00	O—O^i—O^xii	60.00
O—Al^ii—O^xiii	90.00	O—O^ii—O^xv	180.00
La—O—La^xvii	90.00	O—O^ii—O^xiii	60.00
La—O—La^xviii	90.00	O—O^v—O^vi	60.00
La—O—La^xix	180.00	O—O^v—O^xv	60.00
La—O—Al	90.00	O—O^v—O^xiii	180.00
La—O—Al^xx	90.00	O—O^vi—O^xvi	60.00
La—O—O^i	60.00	O—O^vi—O^xii	180.00
La—O—O^ii	60.00	O—O^xv—O^xvi	60.00
La—O—O^v	60.00	O—O^xii—O^xiii	60.00

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