LiYb(PO3)4

inorganic papers

i102

Structure Reports Online

ISSN 1600-5368

LiYb(PO

)

Emna Ben Zarkouna and Ahmed Driss*

Laboratoire de MateÂriaux et Cristallochimie, Faculte des Sciences, Universite Tunis-ElManar, 2092 ElManar, Tunis, Tunisia

Correspondence e-mail: [email protected]

Key indicators

Single-crystal X-ray study T= 293 K

Mean(P±O) = 0.003 AÊ Rfactor = 0.018 wRfactor = 0.047

Data-to-parameter ratio = 11.3

For details of how these key indicators were automatically derived from the article, see http://journals.iucr.org/e.

#2004 International Union of Crystallography Printed in Great Britain ± all rights reserved

The structure of the lithium ytterbium polyphosphate

LiYb(PO3)4 is described. It consists of a three-dimensional

framework made up of spiral (PO3)nchains linked by YbO8

polyhedra. The Li+_{cations reside in the tunnels delimited by}

the framework. The structure is compared with that of some

other compounds like LiNd(PO3)4, NaNd(PO3)4, KNd(PO3)4,

RbNdP4O12and Yb(PO3)3.

Comment

Mixed polyphosphates involving both alkaline and lanthanide cations are of particular importance because of the laser

properties they may exhibit (Yamadaet al., 1974). In order to

discover new materials with interesting optical properties, we

have undertaken the study of the Li2O±Yb2O3±P2O5 system

and have isolated the title compound, LiYb(PO3)4.

As reported in the literature, polyphosphates with the

general formula LiLn(PO3)4[Ln = La (Feridet al., 1981), Ce

(Rzaigui & Ariguib, 1981), Pr (Feridet al., 1998), Sm (Feridet al., 1984) and Er (Liu & Li, 1983)] are isotypic to LiNd(PO3)4

(Hong, 1975a), which is the prototype. Although LiYb(PO3)4

and LiNd(PO3)4 crystallize in the monoclinic system (space

group C2/c) and have similar unit-cell parameters, some

details, especially the position of the Li atoms, make their

structures distinctive. In fact, while in LiNd(PO3)4 the Li+

cations are located on the 4(a) site, they are clearly found by

Fourier difference syntheses at the 4(e) site in the present

Received 6 July 2004 Accepted 14 July 2004 Online 24 July 2004

Figure 1

structure. In both compounds, the Li atoms are tetra-coordinated, but the geometry of their coordination polyhedra

is quite different. In LiYb(PO3)4the Li atom is situated within

a distorted tetrahedron, with OÐLiÐO angles ranging

between 81.8 (5) and 127.0 (1)_{, whereas in LiNd(PO}

3)4, it is

located at the center of a parallelogram. On the basis of

symmetry and bonding considerations, the 4(e) site appears

more suitable for the Li atom than the 4(a) site.

In LiYb(PO3)4, the PO4 tetrahedra share corners to

produce in®nite helical chains running along thebdirection.

(PO3)nchains alternate with ±Yb3+±Li+± rows (Fig. 1). Their

period is four PO4 tetrahedra, as in the structures of the

polyphosphates NaNd(PO3)4(Koizumi, 1976) and KNd(PO3)4

(Hong, 1975b). However, they lie along the c direction in

NaNd(PO3)4and in theadirection in KNd(PO3)4. The

alter-nation of the polyphosphate anions (PO3)44ÿwith the rows of

Yb3+ _{and Li}+ _{cations in LiYb(PO}

3)4 resembles that of the

P4O12 rings with the rows of Nd3+ and Rb+ cations in the

cyclotetraphosphate RbNdP4O12(Koizumi & Nakano, 1977).

On the twofold axes, Li+ _{and Yb}3+ _{ions are arranged}

alter-nately at almost equal spacings (3.496 and 3.528 AÊ), compared

with the quite different spacings of Rb+_{and Nd}3+_{(3.914 and}

8.777 AÊ) in the RbNdP4O12structure. In the title compound,

the Yb atoms are octacoordinated. Each YbO8 polyhedron

shares its O atoms with four adjacent (PO3)nchains (Fig. 2).

The resulting three-dimensional framework delimits tunnels

running along the [101] direction where Li+_{cations are located}

(Fig. 3). The ytterbium coordination polyhedra are isolated

from one another, as in Yb(PO3)3 (Hong, 1974). The

struc-tures of LiYb(PO3)4 and Yb(PO3)3 display shorter Yb Yb

distances of 5.545 and 5.610 AÊ, respectively. In LiYb(PO3)4,

the average values of the P1ÐO, P2ÐO, LiÐO and YbÐO distances are 1.544, 1.540, 1.982 and 2.363 AÊ, respectively. These values are close to those quoted in the literature (Hong & Pierce, 1974; International Tables for X-ray Crystal-lography, 1968, Vol. III). Bond-valence-sum values (Brown & Altermatt, 1985) are 4.92, 4.98, 0.99 and 2.81 for P1, P2, Li and Yb, respectively, and are consistent with the cation charges.

Experimental

The synthesis was carried out by a solid-state reaction with the starting materials Li2CO3(Fluka, 99%), Yb2O3(Prolabo, 99.9%) and

(NH4)2HPO4(Fluka, 99%) in a 4:1:15 molar ratio. These ingredients,

®nely ground, were ®rst heated at 673 K for 5 h and then kept for three weeks at 918 K. A progressive cooling down to 673 K (15 K hÿ1_{) followed by a further cooling to room temperature (100 K h}ÿ1₎

led to crystals of LiYb(PO3)4. Crystal data

LiYb(PO3)4 Mr= 495.86 Monoclinic,C2=c a= 16.194 (3) AÊ

b= 7.024 (1) AÊ

c= 9.498 (2) AÊ = 125.91 (1)

V= 875.0 (3) AÊ3 Z= 4

Dx= 3.764 Mg mÿ3

MoKradiation Cell parameters from 25

re¯ections = 10.0±16.0

= 11.49 mmÿ1 T= 293 (2) K Prism, colorless 0.180.180.14 mm

Data collection

Enraf±Nonius CAD-4 diffractometer !/2scans

Absorption correction: scan (Northet al., 1968)

Tmin= 0.114,Tmax= 0.189 1009 measured re¯ections 950 independent re¯ections 934 re¯ections withI> 2(I)

Rint= 0.028 max= 27.0 h=ÿ16!20

k= 0!8

l=ÿ12!0 2 standard re¯ections

frequency: 120 min intensity decay: 1%

inorganic papers

Acta Cryst.(2004). E60, i102±i104 Zarkouna and Driss LiYb(PO₃)₄

i103

Figure 2

Projection of the LiYb(PO3)4structure along thebdirection, showing the association of the YbO8polyhedra with the (PO3)nchains.

Figure 3

Re®nement

Re®nement onF2 R[F2_{> 2(F}2_{)] = 0.018} wR(F2_{) = 0.047} S= 1.17 950 re¯ections 84 parameters

w= 1/[2_(Fo2_{) + (0.0199P)}2

+ 9.6931P]

whereP= (Fo2_{+ 2Fc}2_)/3

(/)max< 0.001 max= 1.10 e AÊÿ3 min=ÿ1.36 e AÊÿ3

Extinction correction:SHELXL97 Extinction coef®cient: 0.0041 (2)

Table 1

Selected geometric parameters (AÊ,_).

LiÐO2 1.980 (9) LiÐO6i _{1.984 (9)}

YbÐO3ii _{2.259 (3)}

YbÐO1 2.314 (3) YbÐO2iii _{2.383 (3)}

YbÐO6iv _{2.496 (3)}

P1ÐO1 1.491 (3)

P1ÐO6v _{1.500 (3)}

P1ÐO4vi _{1.590 (3)}

P1ÐO5vii _{1.595 (3)}

P2ÐO3 1.486 (3) P2ÐO2 1.487 (3) P2ÐO5 1.585 (3) P2ÐO4 1.601 (3)

O1ÐP1ÐO6v _{118.6 (2)}

O1ÐP1ÐO4vi _{106.9 (2)}

O6v_ÐP1ÐO4vi _{110.7 (2)}

O1ÐP1ÐO5vii _{111.8 (2)}

O6v_ÐP1ÐO5vii _{105.0 (2)}

O4vi_ÐP1ÐO5vii _{102.7 (2)}

O3ÐP2ÐO2 120.0 (2) O3ÐP2ÐO5 111.8 (2) O2ÐP2ÐO5 108.2 (2) O3ÐP2ÐO4 109.7 (2) O2ÐP2ÐO4 104.3 (2) O5ÐP2ÐO4 100.9 (2)

Symmetry codes: (i) 1‡x;y;z; (ii) xÿ1;y;zÿ1; (iii) 1ÿx;ÿy;1ÿz; (iv)

ÿx;1ÿy;1ÿz; (v)x;y;zÿ1; (vi) 1ÿx;1ÿy;1ÿz; (vii)xÿ1

2;12ÿy;zÿ12.

The highest peak in the ®nal difference map is 0.90 AÊ from Yb and the deepest hole is 0.89 AÊ from Yb.

Data collection:CAD-4EXPRESS(Duisenberg, 1992; MacõÂcÏek & Yordanov, 1992); cell re®nement:CAD-4EXPRESS; data reduction:

XCAD4 (Harms & Wocadlo, 1995); program(s) used to solve struc-ture:SHELXS97 (Sheldrick, 1997); program(s) used to re®ne struc-ture:SHELXL97 (Sheldrick, 1997); molecular graphics:DIAMOND

(Brandenburg, 1998); software used to prepare material for publi-cation:SHELXL97.

References

Brandenburg, K. (1998).DIAMOND. Version 2.0. Gerhard-Domagk-Straûe 1, 53121 Bonn, Germany.

Brown, I. D. & Altermatt, D. (1985).Acta Cryst.B41, 244±247. Duisenberg, A. J. M. (1992).J. Appl. Cryst.25, 92±96.

Ferid, M., Ariguib, N. K. & Trabelsi, M. (1981).J. Solid State Chem.38, 133± 137.

Ferid, M., Dogguy, M., Ariguib, N. K. & Trabelsi, M. (1984).J. Solid State Chem.53, 149±154.

Ferid, M., Piriou, B. & Trabelsi-Ayedi, M. (1998).J. Therm. Anal.53, 227±234. Harms, K. & Wocadlo, S. (1995).XCAD4. University of Marburg, Germany. Hong, H. Y.-P. (1974).Acta Cryst.B30, 1857±1861.

Hong, H. Y.-P. (1975a).Mater. Res. Bull.10, 635±640. Hong, H. Y.-P. (1975b).Mater. Res. Bull.10, 1105±1110.

Hong, H. Y.-P. & Pierce, J. W. (1974).Mater. Res. Bull.9, 179±190. Koizumi, H. (1976).Acta Cryst.B32, 2254±2256.

Koizumi, H. & Nakano, J. (1977).Acta Cryst.B33, 2680±2684. Liu, J.-C. & Li, D.-Y. (1983).Acta Phys. Sin.32, 786±790. MacõÂcÏek, J. & Yordanov, A. (1992).J. Appl. Cryst.25, 73±80.

North, A. C. T., Phillips, D. C. & Mathews, F. S. (1968).Acta Cryst.A24, 351± 359.

Rzaigui, M. & Ariguib, N. K. (1981).J. Solid State Chem.39, 309±313. Sheldrick, G. M. (1997). SHELXS97 and SHELXL97. Release 97-2.

University of GoÈttingen, Germany.

Yamada, T., Otsuka, K. & Nakano, J. (1974).J. Appl. Phys.45, 5096±5097.

inorganic papers

supporting information

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Acta Cryst. (2004). E60, i102–i104

supporting information

Acta Cryst. (2004). E60, i102–i104 [https://doi.org/10.1107/S1600536804017283]

LiYb(PO

)

Emna Ben Zarkouna and Ahmed Driss

LiYb(PO3)4

Crystal data LiYb(PO3)4 Mr = 495.86 Monoclinic, C2/c Hall symbol: -C 2yc a = 16.194 (3) Å b = 7.024 (1) Å c = 9.498 (2) Å β = 125.91 (1)° V = 875.0 (3) Å3 Z = 4

F(000) = 916 Dx = 3.764 Mg m−3

Mo Kα radiation, λ = 0.71073 Å Cell parameters from 25 reflections θ = 10.0–16.0°

µ = 11.49 mm−1 T = 293 K Prism, colorless 0.18 × 0.18 × 0.14 mm

Data collection Enraf–Nonius CAD-4

diffractometer

Radiation source: fine-focus sealed tube Graphite monochromator

ω/2θ scans

Absorption correction: ψ scan (North et al., 1968)

Tmin = 0.114, Tmax = 0.189 1009 measured reflections

950 independent reflections 934 reflections with I > 2σ(I) Rint = 0.028

θmax = 27.0°, θmin = 3.1° h = −16→20

k = 0→8 l = −12→0

2 standard reflections every 120 min intensity decay: 1%

Refinement Refinement on F2 Least-squares matrix: full R[F2 _{> 2σ(F}2_{)] = 0.018} wR(F2_{) = 0.047} S = 1.17 950 reflections 84 parameters 0 restraints

Primary atom site location: heavy method

Secondary atom site location: difference Fourier map

w = 1/[σ2_(Fo2_{) + (0.0199P)}2 _{+ 9.6931P]} where P = (Fo2 _{+ 2Fc}2_)/3

(Δ/σ)max < 0.001 Δρmax = 1.10 e Å−3 Δρmin = −1.36 e Å−3

Extinction correction: SHELXL97, Fc*_{=kFc[1+0.001xFc}2_λ3_/sin(2θ)]-1/4 Extinction coefficient: 0.0041 (2)

Special details

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Acta Cryst. (2004). E60, i102–i104

Refinement. Refinement of F2 _{against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F}2_, conventional R-factors R are based on F, with F set to zero for negative F2_{. The threshold expression of F}2 _{> σ(F}2_{) 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 (Å2₎

x y z Uiso*/Ueq

Li 1.0000 0.294 (2) 0.7500 0.015 (2)

Yb 0.0000 0.20382 (3) 0.2500 0.0050 (1)

P1 0.13736 (8) 0.4497 (1) 0.1165 (1) 0.0049 (2)

P2 0.85435 (8) 0.1483 (2) 0.8060 (1) 0.0049 (2)

O1 0.1127 (2) 0.2852 (4) 0.1851 (4) 0.0105 (6)

O2 0.9304 (2) 0.0808 (4) 0.7772 (4) 0.0086 (6)

O3 0.8721 (2) 0.1164 (5) 0.9765 (4) 0.0096 (6)

O4 0.8442 (2) 0.3717 (4) 0.7656 (4) 0.0085 (6)

O5 0.7453 (2) 0.0757 (5) 0.6493 (4) 0.0083 (6)

O6 0.0647 (2) 0.4987 (4) 0.9274 (4) 0.0083 (6)

Atomic displacement parameters (Å2₎

U11 _U22 _U33 _U12 _U13 _U23

Li 0.019 (6) 0.014 (6) 0.015 (6) 0.000 0.012 (5) 0.000

Yb 0.0055 (2) 0.0053 (2) 0.0038 (2) 0.000 0.0026 (1) 0.000

P1 0.0050 (5) 0.0048 (5) 0.0044 (5) 0.0004 (4) 0.0024 (4) 0.0005 (4)

P2 0.0051 (5) 0.0051 (5) 0.0045 (5) −0.0005 (4) 0.0027 (4) −0.0009 (4)

O1 0.012 (2) 0.006 (1) 0.015 (2) 0.000 (1) 0.009 (1) 0.003 (1)

O2 0.010 (1) 0.007 (1) 0.012 (1) −0.001 (1) 0.008 (1) −0.002 (1)

O3 0.010 (1) 0.013 (1) 0.002 (1) −0.002 (1) 0.002 (1) 0.001 (1)

O4 0.015 (1) 0.003 (1) 0.007 (1) 0.001 (1) 0.007 (1) −0.001 (1)

O5 0.006 (1) 0.012 (2) 0.006 (1) −0.003 (1) 0.003 (1) −0.004 (1)

O6 0.007 (1) 0.010 (1) 0.004 (1) 0.001 (1) 0.001 (1) 0.000 (1)

Geometric parameters (Å, º)

Li—O2 1.980 (9) Yb—O6viii _{2.496 (3)}

Li—O2i _{1.980 (9) Yb—O6}ix _{2.496 (3)}

Li—O6ii _{1.984 (9) P1—O1 1.491 (3)}

Li—O6iii _{1.984 (9) P1—O6}x _{1.500 (3)}

Yb—O3iv _{2.259 (3) P1—O4}xi _{1.590 (3)}

Yb—O3iii _{2.259 (3) P1—O5}xii _{1.595 (3)}

Yb—O1v _{2.314 (3) P2—O3 1.486 (3)}

Yb—O1 2.314 (3) P2—O2 1.487 (3)

Yb—O2vi _{2.383 (3) P2—O5 1.585 (3)}

Yb—O2vii _{2.383 (3) P2—O4 1.601 (3)}

O2—Li—O2i _{81.8 (5) O1}v_—Yb—O6viii _{72.4 (1)}

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Acta Cryst. (2004). E60, i102–i104

O2i_—Li—O6ii _{127.0 (1) O2}vi_—Yb—O6viii _{131.8 (1)}

O2—Li—O6iii _{127.0 (1) O2}vii_—Yb—O6viii _{137.5 (1)}

O2i_—Li—O6iii _{119.7 (1) O3}iv_—Yb—O6ix _{73.3 (1)}

O6ii_—Li—O6iii _{87.0 (5) O3}iii_—Yb—O6ix _{137.9 (1)}

O3iv_—Yb—O3iii _{148.4 (2) O1}v_—Yb—O6ix _{83.6 (1)}

O3iv_—Yb—O1v _{92.2 (1) O1—Yb—O6}ix _{72.4 (1)}

O3iii_—Yb—O1v _{95.5 (1) O2}vi_—Yb—O6ix _{137.5 (1)}

O3iv_{—Yb—O1 95.5 (1) O2}vii_—Yb—O6ix _{131.8 (1)}

O3iii_{—Yb—O1 92.2 (1) O6}viii_—Yb—O6ix _{66.3 (1)}

O1v_{—Yb—O1 151.4 (1) O1—P1—O6}x _{118.6 (2)}

O3iv_—Yb—O2vi _{73.9 (1) O1—P1—O4}xi _{106.9 (2)}

O3iii_—Yb—O2vi _{79.6 (1) O6}x_—P1—O4xi _{110.7 (2)}

O1v_—Yb—O2vi _{71.4 (1) O1—P1—O5}xii _{111.8 (2)}

O1—Yb—O2vi _{137.2 (1) O6}x_—P1—O5xii _{105.0 (2)}

O3iv_—Yb—O2vii _{79.6 (1) O4}xi_—P1—O5xii _{102.7 (2)}

O3iii_—Yb—O2vii _{73.9 (1) O3—P2—O2 120.0 (2)}

O1v_—Yb—O2vii _{137.2 (1) O3—P2—O5 111.8 (2)}

O1—Yb—O2vii _{71.4 (1) O2—P2—O5 108.2 (2)}

O2vi_—Yb—O2vii _{65.9 (1) O3—P2—O4 109.7 (2)}

O3iv_—Yb—O6viii _{137.9 (1) O2—P2—O4 104.3 (2)}

O3iii_—Yb—O6viii _{73.3 (1) O5—P2—O4 100.9 (2)}

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