LiTb(PO₃)₄

The lithium terbium polyphosphate LiTb(PO₃)₄ was prepared by the flux method using a large excess of H₃PO₄. It was structurally characterized by single-crystal X-ray diffraction and found to be isotypic with LiYb(PO₃)₄. The basic structural units are endless spiral chains, (PO₃)_n, along the b-axis direction. The Li⁺ and Tb³⁺ cations alternate on twofold axes and are four- and eight-coordinated, respectively. The results of an optical study of this material are also given and discussed.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](P-O) = 0.003 Å
• R factor = 0.020
• wR factor = 0.054
• Data-to-parameter ratio = 11.6

checkCIF/PLATON results

No syntax errors found



Alert level C
CRYSC01_ALERT_1_C The word below has not been recognised as a standard
            identifier.
            colouless
CRYSC01_ALERT_1_C No recognised colour has been given for crystal colour.
PLAT062_ALERT_4_C Rescale T(min) & T(max) by .....................       0.77
PLAT153_ALERT_1_C The su's on the Cell Axes are Equal (x 100000) .        200 Ang.

Alert level G
ABSTM02_ALERT_3_G  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      0.773
            Tmax scaled      0.500 Tmin scaled      0.182
PLAT199_ALERT_1_G Check the Reported _cell_measurement_temperature        293 K
PLAT200_ALERT_1_G Check the Reported _diffrn_ambient_temperature .        293 K

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

   5 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   0 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
   1 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

---

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.

lithium terbium polyphosphate

Crystal data

LiTb(PO3)4	F(000) = 896
Mr = 481.74	Dx = 3.569 Mg m^−3
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71069 Å
Hall symbol: -C 2yc	Cell parameters from 25 reflections
a = 16.358 (2) Å	θ = 10.7–14.7°
b = 7.050 (2) Å	µ = 8.67 mm^−1
c = 9.629 (2) Å	T = 293 K
β = 126.15 (1)°	Plate, colourless
V = 896.7 (4) Å^3	0.28 × 0.16 × 0.08 mm
Z = 4

Data collection

Enraf–Nonius CAD-4 diffractometer	951 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.016
Graphite monochromator	θmax = 26.9°, θmin = 3.1°
ω/2θ scans	h = −20→17
Absorption correction: ψ scan (North et al., 1968)	k = −1→8
Tmin = 0.236, Tmax = 0.646	l = −1→12
1324 measured reflections	2 standard reflections every 120 min
974 independent reflections	intensity decay: 1%

Refinement

Refinement on F^2	Primary atom site location: heavy-atom method
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.020	w = 1/[σ^2(Fo^2) + (0.0344P)^2 + 5.8217P] where P = (Fo^2 + 2Fc^2)/3
wR(F^2) = 0.054	(Δ/σ)max < 0.001
S = 1.08	Δρmax = 1.38 e Å^−3
974 reflections	Δρmin = −1.15 e Å^−3
84 parameters	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
0 restraints	Extinction coefficient: 0.0025 (2)

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
Li	0.0000	0.705 (1)	0.2500	0.018 (2)
Tb	0.0000	0.20252 (3)	0.2500	0.0065 (1)
P1	0.13795 (7)	0.5530 (1)	0.6151 (1)	0.0064 (2)
P2	0.14715 (7)	0.1520 (1)	0.6974 (1)	0.0068 (2)
O1	0.1137 (2)	0.7167 (4)	0.6825 (4)	0.0121 (6)
O2	0.0719 (2)	0.0871 (4)	0.7268 (4)	0.0106 (5)
O3	0.1286 (2)	0.1149 (4)	0.5286 (3)	0.0116 (5)
O4	0.1578 (2)	0.3762 (4)	0.7340 (3)	0.0108 (5)
O5	0.2555 (2)	0.0801 (4)	0.8536 (3)	0.0104 (5)
O6	0.0653 (2)	0.5027 (4)	0.4280 (3)	0.0097 (5)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Li	0.024 (6)	0.016 (6)	0.016 (5)	0.000	0.013 (5)	0.000
Tb	0.0053 (2)	0.0071 (2)	0.0066 (2)	0.000	0.0031 (1)	0.000
P1	0.0045 (4)	0.0069 (5)	0.0069 (4)	−0.0004 (3)	0.0029 (4)	−0.0002 (3)
P2	0.0047 (4)	0.0079 (4)	0.0075 (4)	0.0000 (3)	0.0035 (4)	0.0011 (3)
O1	0.011 (1)	0.012 (1)	0.016 (1)	−0.000 (1)	0.009 (1)	−0.003 (1)
O2	0.006 (1)	0.011 (1)	0.017 (1)	0.000 (1)	0.008 (1)	0.002 (1)
O3	0.012 (1)	0.012 (1)	0.009 (1)	0.001 (1)	0.005 (1)	0.000 (1)
O4	0.016 (1)	0.007 (1)	0.010 (1)	−0.000 (1)	0.008 (1)	0.000 (1)
O5	0.006 (1)	0.016 (1)	0.010 (1)	0.001 (1)	0.005 (1)	0.002 (1)
O6	0.005 (1)	0.012 (1)	0.008 (1)	−0.002 (1)	0.002 (1)	0.000 (1)

Geometric parameters (Å, º)

Li—O2^i	1.974 (8)	Tb—O2^vi	2.432 (3)
Li—O2^ii	1.974 (8)	Tb—O6	2.530 (3)
Li—O6^iii	1.987 (7)	Tb—O6^iii	2.530 (3)
Li—O6	1.987 (7)	P1—O1	1.488 (3)
Li—Tb^iv	3.509 (10)	P1—O6	1.502 (3)
Li—Tb	3.541 (10)	P1—O4	1.591 (3)
Tb—O3^iii	2.312 (3)	P1—O5^vii	1.596 (3)
Tb—O3	2.312 (3)	P2—O2	1.488 (3)
Tb—O1^i	2.374 (3)	P2—O3	1.490 (3)
Tb—O1^ii	2.374 (3)	P2—O5	1.586 (3)
Tb—O2^v	2.432 (3)	P2—O4	1.606 (3)
O2^i—Li—O2^ii	84.0 (4)	O6—P1—O5^vii	105.0 (1)
O2^i—Li—O6^iii	119.23 (11)	O4—P1—O5^vii	102.8 (1)
O2^ii—Li—O6^iii	125.26 (11)	O2—P2—O3	119.6 (2)
O2^i—Li—O6	125.26 (11)	O2—P2—O5	107.9 (1)
O2^ii—Li—O6	119.23 (11)	O3—P2—O5	111.9 (2)
O6^iii—Li—O6	88.4 (4)	O2—P2—O4	104.8 (1)
O1—P1—O6	118.7 (2)	O3—P2—O4	109.8 (1)
O1—P1—O4	106.7 (2)	O5—P2—O4	101.0 (2)
O6—P1—O4	111.1 (1)	P1—O4—P2	131.5 (2)
O1—P1—O5^vii	111.5 (2)	P2—O5—P1^viii	134.6 (2)

Symmetry codes: (i) x, −y+1, z−1/2; (ii) −x, −y+1, −z+1; (iii) −x, y, −z+1/2; (iv) x, y+1, z; (v) −x, −y, −z+1; (vi) x, −y, z−1/2; (vii) −x+1/2, y+1/2, −z+3/2; (viii) −x+1/2, y−1/2, −z+3/2.