Cerium arsenate, CeAsO₄

CeAsO₄ was synthesized by the high-temperature solid-state reaction between CeO₂, K₂CO₃ and (NH₄)H₂AsO₄. The compound is isostructural with compounds of the monazite structure type. The structure is built up from CeO₈ bis-disphenoids and AsO₄ tetrahedra, joined by corners and edges.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](As-O) = 0.007 Å
• R factor = 0.031
• wR factor = 0.082
• Data-to-parameter ratio = 12.7

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry

General Notes



ABSTM_02  When printed, the submitted absorption T values will be replaced
          by the scaled T values. Since the ratio of scaled T's is
          identical to the ratio of reported T values, the scaling does
          not imply a change to the absorption corrections used in the
          study.
          Ratio of Tmax expected/reported      0.925
          Tmax scaled      0.490 Tmin scaled      0.203

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Computing details

Data collection: CAD-4 EXPRESS (Duisenberg, 1992; Macíček & Yordanov, 1992); cell refinement: CAD-4 EXPRESS; data reduction: MolEN (Fair, 1990); program(s) used to solve structure: SHELXS86 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: DIAMOND (Brandenburg, 1998); software used to prepare material for publication: SHELXL97.

cerium arsenate

Crystal data

CeAsO4	F(000) = 492
Mr = 279.03	Dx = 5.663 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71069 Å
Hall symbol: -P 2yn	Cell parameters from 25 reflections
a = 6.975 (1) Å	θ = 2.8–28.0°
b = 7.177 (1) Å	µ = 23.77 mm^−1
c = 6.759 (2) Å	T = 293 K
β = 104.69 (1)°	Parallelepiped, colorless
V = 327.29 (12) Å^3	0.1 × 0.06 × 0.03 mm
Z = 4

Data collection

Enraf-Nonius CAD-4 diffractometer	681 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.024
Graphite monochromator	θmax = 27.0°, θmin = 3.8°
ω/2θ scans	h = −8→8
Absorption correction: ψ scan (North et al. 1968)	k = −9→9
Tmin = 0.22, Tmax = 0.53	l = −8→0
1478 measured reflections	2 standard reflections every 120 min
712 independent reflections	intensity decay: 0.4%

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.031	w = 1/[σ^2(Fo^2) + (0.0592P)^2] where P = (Fo^2 + 2Fc^2)/3
wR(F^2) = 0.082	(Δ/σ)max = 0.03
S = 1.24	Δρmax = 1.97 e Å^−3
712 reflections	Δρmin = −3.18 e Å^−3
56 parameters	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
0 restraints	Extinction coefficient: 1263 (56)

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
Ce	0.21913 (8)	0.15370 (8)	0.40111 (8)	0.0203 (4)
As	0.19637 (17)	0.16297 (13)	0.88645 (15)	0.0197 (4)
O1	0.1098 (12)	0.3406 (8)	0.0013 (12)	0.0257 (16)
O2	0.0155 (10)	0.1083 (10)	0.6742 (10)	0.0256 (13)
O3	0.2457 (10)	−0.0040 (10)	0.0691 (9)	0.0246 (14)
O4	0.3808 (10)	0.2171 (11)	0.7766 (10)	0.0255 (13)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Ce	0.0203 (5)	0.0195 (6)	0.0212 (5)	0.00000 (14)	0.0051 (3)	−0.00056 (15)
As	0.0199 (7)	0.0196 (7)	0.0197 (7)	0.0002 (3)	0.0053 (5)	0.0001 (3)
O1	0.028 (4)	0.023 (4)	0.030 (4)	0.000 (2)	0.012 (3)	−0.004 (2)
O2	0.023 (3)	0.026 (3)	0.026 (3)	−0.001 (3)	0.003 (3)	−0.002 (3)
O3	0.031 (3)	0.018 (3)	0.024 (3)	0.000 (3)	0.007 (3)	0.002 (2)
O4	0.026 (3)	0.027 (3)	0.026 (3)	0.001 (3)	0.011 (3)	0.002 (3)

Geometric parameters (Å, º)

Ce—O2^i	2.460 (7)	Ce—O2	2.619 (7)
Ce—O3^ii	2.472 (7)	Ce—O1^v	2.636 (8)
Ce—O4^iii	2.476 (7)	As—O1^vi	1.683 (6)
Ce—O4	2.543 (7)	As—O4	1.685 (7)
Ce—O1^iv	2.551 (7)	As—O3^vi	1.692 (7)
Ce—O3	2.562 (6)	As—O2	1.699 (7)
O1^vi—As—O4	115.6 (4)	O1^vi—As—O2	106.7 (4)
O1^vi—As—O3^vi	103.3 (3)	O4—As—O2	99.7 (3)
O4—As—O3^vi	116.6 (3)	O3^vi—As—O2	115.0 (4)

Symmetry codes: (i) −x, −y, −z+1; (ii) −x+1/2, y+1/2, −z+1/2; (iii) x−1/2, −y+1/2, 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, y, z+1.