Ag₃Nb(NbO)₂O₄(AsO₄)₂

The title compound, trisilver niobium niobate tetraoxide bis(arsenate), contains (NbAsO₈)_n corrugated layers crosslinked via NbO₆ polyhedra to form a three-dimensional framework that delimits elliptical tunnels running along the a axis where the highly disordered Ag⁺ cations are located.

Key indicators

• Single-crystal X-ray study
• T = 298 K
• Mean [sigma](As-O) = 0.005 Å
• R factor = 0.032
• wR factor = 0.086
• Data-to-parameter ratio = 10.6

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT041_ALERT_1_C Calc. and Rep. SumFormula Strings    Differ ....          ?
PLAT042_ALERT_1_C Calc. and Rep. MoietyFormula Strings Differ ....          ?
PLAT068_ALERT_1_C Reported F000 Differs from Calcd (or Missing)...          ?
PLAT152_ALERT_1_C Supplied and Calc Volume s.u. Inconsistent .....          ?
PLAT213_ALERT_2_C Atom Ag1     has ADP max/min Ratio .............       3.10 prolat
PLAT213_ALERT_2_C Atom Ag2     has ADP max/min Ratio .............       3.10 prolat
PLAT213_ALERT_2_C Atom Ag3     has ADP max/min Ratio .............       3.10 prolat
PLAT213_ALERT_2_C Atom Ag4     has ADP max/min Ratio .............       3.10 prolat
PLAT213_ALERT_2_C Atom Ag5     has ADP max/min Ratio .............       3.10 prolat
PLAT213_ALERT_2_C Atom Ag6     has ADP max/min Ratio .............       3.10 prolat
PLAT213_ALERT_2_C Atom Ag7     has ADP max/min Ratio .............       3.10 prolat
PLAT250_ALERT_2_C Large U3/U1 Ratio for Average U(i,j) Tensor ....       2.34
PLAT301_ALERT_3_C Main Residue  Disorder .........................       9.00 Perc.

   0 ALERT level A = In general: serious problem
   0 ALERT level B = Potentially serious problem
  13 ALERT level C = Check and explain
   0 ALERT level G = General alerts; check

   4 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   8 ALERT type 2 Indicator that the structure model may be wrong or deficient
   1 ALERT type 3 Indicator that the structure quality may be low
   0 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

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Computing details

Data collection: CAD-4 EXPRESS (Duisenberg, 1992; Macíček & Yordanov, 1992); cell refinement: CAD-4 EXPRESS; data reduction: XCAD4 (Harms & Wocadlo, 1995); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: DIAMOND (Brandenburg, 1998); software used to prepare material for publication: SHELXL97.

trisilver niobium niobate tetraoxide bis(arsenate)

Crystal data

Ag3Nb(NbO)2O4(AsO4)2	F(000) = 884
Mr = 976.18	Dx = 5.392 Mg m^−3 Dm = non Mg m^−3 Dm measured by not measured
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 25 reflections
a = 5.087 (1) Å	θ = 10–16°
b = 8.713 (1) Å	µ = 13.09 mm^−1
c = 13.740 (1) Å	T = 298 K
β = 99.11 (1)°	Prism, colourless
V = 601.3 (1) Å^3	0.20 × 0.10 × 0.07 mm
Z = 2

Data collection

Enraf–Nonius CAD-4 diffractometer	1169 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.035
Graphite monochromator	θmax = 27.0°, θmin = 2.8°
ω/2θ scans	h = −6→2
Absorption correction: ψ scan (North et al., 1968)	k = −1→11
Tmin = 0.226, Tmax = 0.400	l = −17→17
1962 measured reflections	2 standard reflections every 120 min
1299 independent reflections	intensity decay: 1%

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)] = 0.032	w = 1/[σ^2(Fo^2) + (0.0366P)^2 + 6.6131P] where P = (Fo^2 + 2Fc^2)/3
wR(F^2) = 0.086	(Δ/σ)max = 0.007
S = 1.12	Δρmax = 1.20 e Å^−3
1299 reflections	Δρmin = −1.40 e Å^−3
123 parameters	Extinction correction: SHELXL97 (Sheldrick, 1997), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
1 restraint	Extinction coefficient: 0.0049 (4)

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)
Nb1	0.0000	0.0000	0.0000	0.0073 (2)
Nb2	0.44754 (11)	0.26212 (7)	0.37485 (4)	0.00598 (19)
As1	−0.12198 (13)	0.08243 (8)	0.23368 (5)	0.00501 (19)
Ag1	0.544 (3)	0.3606 (7)	0.1152 (3)	0.0155 (4)	0.433 (11)
Ag2	−0.003 (2)	0.4912 (11)	0.0141 (3)	0.0155 (4)	0.295 (9)
Ag3	0.461 (3)	0.3376 (11)	0.1093 (3)	0.0155 (4)	0.361 (10)
Ag4	0.378 (4)	0.3092 (17)	0.1072 (7)	0.0155 (4)	0.098 (9)
Ag5	0.022 (3)	0.4553 (18)	0.0066 (11)	0.0155 (4)	0.132 (10)
Ag6	0.0225 (18)	0.4223 (9)	0.0463 (7)	0.0155 (4)	0.091 (2)
Ag7	0.634 (5)	0.3762 (17)	0.1147 (10)	0.0155 (4)	0.087 (9)
O1	0.3248 (9)	−0.0710 (5)	0.0833 (3)	0.0100 (9)
O2	−0.0838 (10)	0.1251 (6)	0.1156 (3)	0.0101 (10)
O3	0.1654 (10)	0.0933 (6)	0.3122 (4)	0.0128 (10)
O4	−0.2388 (9)	−0.0968 (5)	0.2425 (3)	0.0086 (9)
O5	−0.3465 (10)	0.2162 (6)	0.2564 (3)	0.0111 (10)
O6	0.1933 (9)	0.3210 (6)	0.4590 (3)	0.0100 (10)
O7	0.6287 (10)	0.1112 (6)	0.4462 (4)	0.0125 (10)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Nb1	0.0077 (4)	0.0093 (4)	0.0052 (4)	0.0007 (3)	0.0025 (3)	−0.0003 (3)
Nb2	0.0056 (3)	0.0082 (3)	0.0034 (3)	0.0021 (2)	−0.0017 (2)	−0.0002 (2)
As1	0.0046 (3)	0.0068 (3)	0.0033 (3)	−0.0002 (2)	−0.0005 (2)	−0.0012 (2)
Ag1	0.0182 (12)	0.0132 (16)	0.0139 (6)	−0.0122 (16)	−0.0010 (18)	0.0029 (8)
Ag2	0.0182 (12)	0.0132 (16)	0.0139 (6)	−0.0122 (16)	−0.0010 (18)	0.0029 (8)
Ag3	0.0182 (12)	0.0132 (16)	0.0139 (6)	−0.0122 (16)	−0.0010 (18)	0.0029 (8)
Ag4	0.0182 (12)	0.0132 (16)	0.0139 (6)	−0.0122 (16)	−0.0010 (18)	0.0029 (8)
Ag5	0.0182 (12)	0.0132 (16)	0.0139 (6)	−0.0122 (16)	−0.0010 (18)	0.0029 (8)
Ag6	0.0182 (12)	0.0132 (16)	0.0139 (6)	−0.0122 (16)	−0.0010 (18)	0.0029 (8)
Ag7	0.0182 (12)	0.0132 (16)	0.0139 (6)	−0.0122 (16)	−0.0010 (18)	0.0029 (8)
O1	0.010 (2)	0.007 (2)	0.012 (2)	0.0026 (19)	−0.0020 (18)	0.0032 (18)
O2	0.014 (2)	0.013 (2)	0.005 (2)	0.0020 (19)	0.0041 (18)	−0.0009 (18)
O3	0.012 (2)	0.012 (2)	0.011 (2)	0.000 (2)	−0.0080 (19)	−0.0015 (19)
O4	0.010 (2)	0.010 (2)	0.004 (2)	−0.0036 (19)	−0.0030 (17)	0.0008 (18)
O5	0.012 (2)	0.012 (2)	0.009 (2)	0.0039 (19)	0.0038 (18)	−0.0003 (19)
O6	0.010 (2)	0.012 (2)	0.009 (2)	0.0024 (19)	0.0034 (17)	−0.0009 (19)
O7	0.013 (2)	0.013 (2)	0.010 (2)	0.001 (2)	−0.0036 (19)	0.0037 (19)

Geometric parameters (Å, º)

Nb1—O1^i	1.955 (5)	Ag1—O7^iv	2.452 (6)
Nb1—O1	1.955 (5)	Ag2—O7^vii	2.149 (11)
Nb1—O2^i	2.026 (5)	Ag2—O7^iv	2.166 (11)
Nb1—O2	2.026 (5)	Ag3—O5^v	2.353 (7)
Nb1—O6^ii	1.973 (5)	Ag3—O7^iv	2.522 (9)
Nb1—O6^iii	1.973 (5)	Ag3—O4^vi	2.545 (8)
Nb2—O7	1.804 (5)	Ag3—O7^ii	2.560 (10)
Nb2—O6	1.935 (5)	Ag4—O4^vi	2.429 (12)
Nb2—O1^iv	1.891 (5)	Ag4—O5^v	2.430 (11)
Nb2—O5^v	2.109 (5)	Ag4—O6^ii	2.390 (13)
Nb2—O3	2.138 (5)	Ag5—O7^vii	2.123 (16)
Nb2—O4^vi	2.168 (5)	Ag5—O7^iv	2.248 (16)
As1—O3	1.676 (5)	Ag6—O7^vii	2.262 (10)
As1—O4	1.682 (5)	Ag6—O7^iv	2.410 (9)
As1—O5	1.695 (5)	Ag7—O3^iv	2.304 (17)
As1—O2	1.706 (5)	Ag7—O7^ii	2.315 (14)
Ag1—O5^v	2.306 (6)	Ag7—O5^v	2.383 (17)
Ag1—O7^ii	2.441 (6)	Ag7—O7^iv	2.514 (18)
O1^i—Nb1—O1	180.0 (4)	O7—Nb2—O5^v	90.4 (2)
O1^i—Nb1—O2^i	88.6 (2)	O6—Nb2—O5^v	166.4 (2)
O1—Nb1—O2^i	91.4 (2)	O1^iv—Nb2—O5^v	91.5 (2)
O1^i—Nb1—O2	91.4 (2)	O7—Nb2—O3	88.3 (2)
O1—Nb1—O2	88.6 (2)	O6—Nb2—O3	87.3 (2)
O2^i—Nb1—O2	180.0 (3)	O1^iv—Nb2—O3	172.3 (2)
O1^i—Nb1—O6^ii	89.8 (2)	O5^v—Nb2—O3	86.7 (2)
O1—Nb1—O6^ii	90.2 (2)	O7—Nb2—O4^vi	165.0 (2)
O2^i—Nb1—O6^ii	91.44 (19)	O6—Nb2—O4^vi	89.95 (19)
O2—Nb1—O6^ii	88.56 (19)	O1^iv—Nb2—O4^vi	89.7 (2)
O1^i—Nb1—O6^iii	90.2 (2)	O5^v—Nb2—O4^vi	77.18 (18)
O1—Nb1—O6^iii	89.8 (2)	O3—Nb2—O4^vi	82.66 (19)
O2^i—Nb1—O6^iii	88.56 (19)	O3—As1—O4	106.7 (2)
O2—Nb1—O6^iii	91.44 (19)	O3—As1—O5	112.8 (2)
O6^ii—Nb1—O6^iii	180.0 (3)	O4—As1—O5	111.6 (2)
O7—Nb2—O6	101.6 (2)	O3—As1—O2	112.4 (2)
O7—Nb2—O1^iv	99.2 (2)	O4—As1—O2	111.5 (2)
O6—Nb2—O1^iv	92.8 (2)	O5—As1—O2	101.9 (2)

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