K(0.8)Ag(0.2)Nb(4)O(9)AsO(4).

The title compound, potassium silver tetra-niobium nona-oxide arsenate, K(0.8)Ag(0.2)Nb(4)O(9)AsO(4), was prepared by a solid-state reaction at 1183 K. The structure consists of infinite (Nb(2)AsO(14))(n) chains parallel to the b axis and cross-linked by corner sharing via pairs of edge-sharing octa-hedra. Each pair links together four infinite chains to form a three-dimensional framework. The K(+) and Ag(+) ions partially occupy several independent close positions in the inter-connected cavities delimited by the framework. K(0.8)Ag(0.2)Nb(4)O(9)AsO(4) is likely to exhibit fast alkali-ion mobility and ion-exchange properties. The Wyckoff symbols of special positions are as follows: one Nb 8e, one Nb 8g, As 4c, two K 8f, one Ag 8f, one Ag 4c, one O 8g, one O 4c.

Littérature associée

Pour le contexte général du travail et structures associées, voir: Ben Amor & Zid (2006 ▶); Benhamada et al. (1992 ▶); Bestaoui et al. (1998 ▶); Brown & Altermatt (1985 ▶); Haddad, Jouini & Ghedira (1988 ▶); Haddad, Jouini et al. (1988 ▶); Harrison et al. (1994 ▶); Ledain et al. (1997 ▶); Piffard et al. (1985 ▶); Zid et al. (1989 ▶, 1992 ▶, 1998 ▶, 2005 ▶).

Partie expérimentale

Données cristallines

K0.8Ag0.2Nb4O9AsO4

M = 707.41

Orthorhombique,

a = 10.469 (2) Å

b = 10.403 (2) Å

c = 10.047 (1) Å

V = 1094.2 (3) Å3

Z = 4

Radiation Mo Kα

μ = 7.81 mm−1

T = 298 (2) K

0.20 × 0.14 × 0.10 mm

Collection des données

Diffractomètre Enraf–Nonius CAD-4

Correction d’absorption: ψ scan (North et al., 1968 ▶) T min = 0.24, T max = 0.45

2162 réflexions mesurées

803 réflexions independantes

751 réflexions avec I > 2σ(I)

R int = 0.024

2 réflexions de référence fréquence: 120 min variation d’intensité: 0.9%

Affinement

R[F 2 > 2σ(F 2)] = 0.024

wR(F 2) = 0.067

S = 1.13

803 réflexions

68 paramètres

Δρmax = 0.90 e Å−3

Δρmin = −1.64 e Å−3

Collection des données: CAD-4 EXPRESS (Duisenberg, 1992 ▶; Macíček & Yordanov, 1992 ▶); affinement des paramètres de la maille: CAD-4 EXPRESS; réduction des données: XCAD4 (Harms & Wocadlo, 1995 ▶); programme(s) pour la solution de la structure: SHELXS97 (Sheldrick, 2008 ▶); programme(s) pour l’affinement de la structure: SHELXL97 (Sheldrick, 2008 ▶); graphisme moléculaire: DIAMOND (Brandenburg, 1998 ▶); logiciel utilisé pour préparer le matériel pour publication: WinGX (Farrugia, 1999 ▶).

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536808015225/fj2116sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S1600536808015225/fj2116Isup2.hkl

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

K0.8Ag0.2Nb4O9AsO4	F000 = 1302
Mr = 707.41	Dx = 4.294 Mg m−3
Orthorhombic, Cmcm	Mo Kα radiation λ = 0.71073 Å
Hall symbol: -C 2c 2	Cell parameters from 25 reflections
a = 10.469 (2) Å	θ = 12–16º
b = 10.403 (2) Å	µ = 7.81 mm−1
c = 10.047 (1) Å	T = 298 (2) K
V = 1094.2 (3) Å3	Prism, colourless
Z = 4	0.20 × 0.14 × 0.10 mm

Enraf–Nonius CAD-4 diffractometer	Rint = 0.024
Radiation source: fine-focus sealed tube	θmax = 29.0º
Monochromator: graphite	θmin = 2.8º
T = 298(2) K	h = −14→14
ω/2θ scans	k = −1→14
Absorption correction: ψ scan(North et al., 1968)	l = −13→3
Tmin = 0.24, Tmax = 0.45	2 standard reflections
2162 measured reflections	every 120 min
803 independent reflections	intensity decay: 0.9%
751 reflections with I > 2σ(I)

Refinement on F2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	w = 1/[σ2(Fo2) + (0.0323P)2 + 10.2211P] where P = (Fo2 + 2Fc2)/3
R[F2 > 2σ(F2)] = 0.024	(Δ/σ)max < 0.001
wR(F2) = 0.067	Δρmax = 0.90 e Å−3
S = 1.13	Δρmin = −1.64 e Å−3
803 reflections	Extinction correction: SHELXL97 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
68 parameters	Extinction coefficient: 0.0031 (2)
Primary atom site location: structure-invariant direct methods

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)
Nb1	0.17473 (4)	0.5000	0.0000	0.00668 (16)
Nb2	0.17121 (4)	0.22837 (4)	0.2500	0.00689 (16)
As1	0.0000	0.66228 (7)	0.2500	0.0081 (2)
K1	0.0000	0.0628 (6)	−0.0585 (8)	0.0213 (10)	0.29
K2	0.0000	0.0484 (15)	0.871 (5)	0.024 (5)*	0.111 (15)
Ag1	0.0000	0.0492 (8)	0.682 (2)	0.021 (3)*	0.070 (6)
Ag2	0.0000	0.0513 (14)	0.7500	0.031 (5)*	0.064 (6)
O1	0.0000	0.5676 (4)	0.1112 (4)	0.0077 (7)
O2	0.3722 (3)	0.2588 (4)	0.2500	0.0114 (8)
O3	0.2170 (3)	0.0783 (3)	0.1151 (3)	0.0114 (5)
O4	0.1491 (3)	0.3420 (3)	0.1103 (3)	0.0124 (6)
O5	0.0000	0.1590 (5)	0.2500	0.0112 (11)

	U11	U22	U33	U12	U13	U23
Nb1	0.0062 (2)	0.0079 (2)	0.0059 (3)	0.000	0.000	−0.00167 (15)
Nb2	0.0065 (2)	0.0056 (2)	0.0085 (3)	0.00101 (15)	0.000	0.000
As1	0.0069 (3)	0.0087 (4)	0.0086 (4)	0.000	0.000	0.000
K1	0.010 (2)	0.030 (3)	0.024 (3)	0.000	0.000	0.001 (2)
O1	0.0081 (16)	0.0094 (16)	0.0057 (17)	0.000	0.000	−0.0051 (14)
O2	0.0039 (16)	0.0103 (18)	0.020 (2)	0.0024 (13)	0.000	0.000
O3	0.0111 (12)	0.0123 (12)	0.0110 (13)	0.0010 (11)	0.0026 (10)	−0.0036 (10)
O4	0.0119 (12)	0.0123 (13)	0.0130 (15)	−0.0001 (11)	−0.0003 (11)	0.0069 (11)
O5	0.006 (2)	0.012 (3)	0.016 (3)	0.000	0.000	0.000

Nb1—O3i	1.813 (3)	K1—O3vii	2.764 (5)
Nb1—O3ii	1.813 (3)	K1—O3viii	2.764 (5)
Nb1—O4	2.001 (3)	K1—O3	2.869 (6)
Nb1—O4iii	2.001 (3)	K1—O3ix	2.869 (6)
Nb1—O1iv	2.256 (2)	K1—O2x	2.989 (6)
Nb1—O1	2.256 (2)	K2—O5xi	2.48 (3)
Nb2—O4v	1.849 (3)	K2—O3xi	2.630 (9)
Nb2—O4	1.849 (3)	K2—O3xii	2.630 (9)
Nb2—O5	1.932 (2)	K2—O2xiii	2.70 (2)
Nb2—O3	2.122 (3)	K2—O2xiv	2.70 (2)
Nb2—O3v	2.122 (3)	Ag1—O5xi	2.272 (11)
Nb2—O2	2.128 (4)	Ag1—O2xiii	2.500 (10)
As1—O2i	1.672 (4)	Ag1—O2xiv	2.500 (10)
As1—O2vi	1.672 (4)	Ag2—O5xi	2.188 (15)
As1—O1	1.707 (4)	Ag2—O2xiii	2.386 (13)
As1—O1v	1.707 (4)	Ag2—O2xiv	2.386 (13)
O3i—Nb1—O3ii	102.60 (18)	O4v—Nb2—O3	169.44 (12)
O3i—Nb1—O4	95.73 (12)	O4—Nb2—O3	90.79 (12)
O3ii—Nb1—O4	93.90 (12)	O5—Nb2—O3	86.27 (14)
O3i—Nb1—O4iii	93.90 (12)	O4v—Nb2—O3v	90.79 (12)
O3ii—Nb1—O4iii	95.73 (12)	O4—Nb2—O3v	169.44 (12)
O4—Nb1—O4iii	164.57 (17)	O5—Nb2—O3v	86.27 (14)
O3i—Nb1—O1iv	164.38 (12)	O3—Nb2—O3v	79.39 (16)
O3ii—Nb1—O1iv	92.92 (12)	O4v—Nb2—O2	91.67 (11)
O4—Nb1—O1iv	84.79 (13)	O4—Nb2—O2	91.67 (11)
O4iii—Nb1—O1iv	82.70 (13)	O5—Nb2—O2	166.61 (19)
O3i—Nb1—O1	92.92 (12)	O3—Nb2—O2	83.44 (11)
O3ii—Nb1—O1	164.38 (12)	O3v—Nb2—O2	83.44 (11)
O4—Nb1—O1	82.70 (13)	O2i—As1—O2vi	106.2 (3)
O4iii—Nb1—O1	84.79 (13)	O2i—As1—O1	110.25 (10)
O1iv—Nb1—O1	71.64 (15)	O2vi—As1—O1	110.25 (10)
O4v—Nb2—O4	98.72 (19)	O2i—As1—O1v	110.25 (10)
O4v—Nb2—O5	97.03 (14)	O2vi—As1—O1v	110.25 (10)
O4—Nb2—O5	97.03 (14)	O1—As1—O1v	109.6 (3)

Table 1

Paramètres géométriques (Å)

Nb1—O3i	1.813 (3)
Nb1—O4	2.001 (3)
Nb1—O1	2.256 (2)
Nb2—O4	1.849 (3)
Nb2—O5	1.932 (2)
Nb2—O3	2.122 (3)
Nb2—O2	2.128 (4)
As1—O2i	1.672 (4)
As1—O1	1.707 (4)
K1—O3ii	2.764 (5)
K1—O3	2.869 (6)
K1—O2iii	2.989 (6)
K2—O5iv	2.48 (3)
K2—O3iv	2.630 (9)
K2—O2v	2.70 (2)
Ag1—O5iv	2.272 (11)
Ag1—O2v	2.500 (10)
Ag2—O5iv	2.188 (15)
Ag2—O2v	2.386 (13)

Codes de symétrie : (i) ; (ii) ; (iii) ; (iv) ; (v) .