inorganic compounds\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

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LiHo(PO3)4

aLaboratoire de Matériaux et Cristallochimie, Faculté des Sciences, Université Tunis-El Manar, 2092 El Manar, Tunis, Tunisia, and bUnité de Matériaux de Terres Rares, Centre National de Recherches en Sciences des Matériaux, BP 95 Hammam-Lif, Tunis 2050, Tunisia
*Correspondence e-mail: emna_benzarkouna@yahoo.fr

(Received 9 January 2009; accepted 14 January 2009; online 23 January 2009)

Lithium holmium(III) polyphosphate(V), LiHo(PO3)4, belongs to the type I of polyphosphates with general formula ALn(PO3)4, where A is a monovalent cation and Ln is a trivalent rare earth cation. In the crystal structure, the polyphosphate chains spread along the b-axis direction, with a repeat period of four tetra­hedra and 21 inter­nal symmetry. The Li and Ho atoms are both located on twofold rotation axes and are surrounded by four and eight O atoms, leading to a distorted tetra­hedral and dodeca­hedral coordination, respectively. The HoO8 polyhedra are isolated from each other, the closest Ho⋯Ho distance being 5.570 (1) Å.

Related literature

For isotypic LiLn(PO3)4 structures, see: Ben Zarkouna & Driss (2004[Ben Zarkouna, E. & Driss, A. (2004). Acta Cryst. E60, i102-i104.]) for Ln = Yb; Ben Zarkouna et al. (2005[Ben Zarkouna, E., Férid, M. & Driss, A. (2005). Mater. Res. Bull. 40, 1985-1992.]) for Ln = Er; Ben Zarkouna et al. (2007[Ben Zarkouna, E., Horchani-Naifer, K., Férid, M. & Driss, A. (2007). Acta Cryst. E63, i1-i2.]) for Ln = Tb. For related structures, see: Amami et al. (2004[Amami, J., Horchani, K., Merle, D. & Férid, M. (2004). J. Phys. IV Fr. 122, 111-115.]) (NaHo(PO3)4); Palkina et al. (1976[Palkina, K. K., Kuznetsov, V. G., Chudinova, N. N. & Chibiskova, N. T. (1976). Izv. Akad. Nauk SSSR Neorg. Mater. 12, 730-734.]) (β-KHo(PO3)4); Tranqui et al. (1972[Tranqui, D., Bagieu-Beucher, M. & Durif, A. (1972). Bull. Soc. Fr. Minéral. Cryst. 95, 437-440.]) (HoP5O14). For general background, see: Brown & Altermatt (1985[Brown, I. D. & Altermatt, D. (1985). Acta Cryst. B41, 244-247.]); Durif (1995[Durif, A. (1995). Crystal Chemistry of Condensed Phosphates. New York: Plenum Press.]); Liu et al. (1999[Liu, G. K., Chen, Y. H. & Beitz, J. V. (1999). J. Lumin. 81, 7-12.]); Palkina et al. (1981[Palkina, K. K., Chudinova, N. N., Litvin, B. N. & Vinogradova, N. V. (1981). Izv. Akad. Nauk SSSR Neorg. Mater. 17, 1501-1503.]); Inter­national Tables for X-Ray Crystallography (1968[International Tables for X-ray Crystallography (1968). Vol. III, 2nd ed. Birmingham: Kynoch Press.]).

Experimental

Crystal data
  • LiHo(PO3)4

  • Mr = 487.75

  • Monoclinic, C 2/c

  • a = 16.280 (3) Å

  • b = 7.039 (2) Å

  • c = 9.561 (2) Å

  • β = 125.99 (2)°

  • V = 886.5 (4) Å3

  • Z = 4

  • Mo Kα radiation

  • μ = 9.72 mm−1

  • T = 293 (2) K

  • 0.31 × 0.14 × 0.07 mm

Data collection
  • Enraf–Nonius CAD-4 diffractometer

  • Absorption correction: ψ scan (North et al., 1968[North, A. C. T., Phillips, D. C. & Mathews, F. S. (1968). Acta Cryst. A24, 351-359.]) Tmin = 0.095, Tmax = 0.378 (expected range = 0.128–0.507)

  • 1500 measured reflections

  • 1078 independent reflections

  • 1076 reflections with I > 2σ(I)

  • Rint = 0.016

  • 2 standard reflections frequency: 120 min intensity decay: none

Refinement
  • R[F2 > 2σ(F2)] = 0.025

  • wR(F2) = 0.071

  • S = 1.12

  • 1078 reflections

  • 84 parameters

  • Δρmax = 2.75 e Å−3

  • Δρmin = −3.18 e Å−3

Table 1
Selected bond lengths (Å)

Li—O2i 1.962 (9)
Li—O6 1.999 (9)
Ho—O3 2.287 (3)
Ho—O1i 2.348 (4)
Ho—O2ii 2.411 (3)
Ho—O6 2.516 (3)
P1—O1 1.488 (4)
P1—O6 1.499 (3)
P1—O4 1.589 (4)
P1—O5iii 1.594 (3)
P2—O2 1.486 (3)
P2—O3 1.488 (3)
P2—O5 1.588 (3)
P2—O4 1.601 (4)
Symmetry codes: (i) [x, -y+1, z-{\script{1\over 2}}]; (ii) [x, -y, z-{\script{1\over 2}}]; (iii) [-x+{\script{1\over 2}}, y+{\script{1\over 2}}, -z+{\script{3\over 2}}].

Data collection: CAD-4 EXPRESS (Duisenberg, 1992[Duisenberg, A. J. M. (1992). J. Appl. Cryst. 25, 92-96.]; Macíček & Yordanov, 1992[Macíček, J. & Yordanov, A. (1992). J. Appl. Cryst. 25, 73-80.]); cell refinement: CAD-4 EXPRESS; Macíček & Yordanov, 1992[Macíček, J. & Yordanov, A. (1992). J. Appl. Cryst. 25, 73-80.]); data reduction: XCAD4 (Harms & Wocadlo, 1995[Harms, K. & Wocadlo, S. (1995). XCAD4. University of Marburg, Germany.]); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); molecular graphics: DIAMOND (Brandenburg, 1998[Brandenburg, K. (1998). DIAMOND. Crystal Impact GbR, Bonn, Germany.]); software used to prepare material for publication: SHELXL97.

Supporting information


Comment top

The present paper is an extension of our earlier work on polyphosphates of general formula LiLn(PO3)4 [Ln = Yb (Ben Zarkouna & Driss, 2004), Er (Ben Zarkouna et al., 2005) and Tb (Ben Zarkouna et al., 2007)]. This family is now expanded to include the lithium holmium polyphosphate, LiHo(PO3)4, which might be of particular interest in the area of luminescent materials, because an avalanche up-conversion emission was observed previously for Ho3+-containing compounds (Liu et al., 1999).

The LiLn(PO3)4 polyphosphates are isostructural and belong to form I according to the classification of Palkina et al. (1981). In this type of arrangement, helical ribbons, (PO3)n, formed by corner-sharing of PO4 tetrahedra, spread parallel to the b axis. The period of the chains corresponds to four tetrahedra but, owing to the presence of 21 screw axes, only two of them are crystallographically independent. The P—O bonds involving terminal O atoms are the shortest within a PO4 tetrahedron, because of the dπ-pπ orbital overlap (Durif, 1995). In LiHo(PO3)4, the mean P—O bond lengths for terminal and bridging O atoms, are of 1.490 and 1.593 Å, respectively. The O—P—O angles are within the range 101.2 (2)–119.6 (2) °, the smallest and the largest ones are those involving the longest and the shortest P—O bonds, respectively. The P—O—P bridges exhibit angles of 131.6 (2) and 134.8 (2)°, larger than the O—P—O angles. The Li and Ho atoms are arranged alternately on twofold rotation axes at roughly similar spacings [3.486 (1) and 3.553 (1) Å] in comparison with the quite different spacings between K and Ho atoms [3.721 (2) and 8.589 (2) Å] in β-KHo(PO3)4 (Palkina et al., 1976). The Ho atom is surrounded by eight terminal oxygen atoms forming a distorted dodecahedron, with an average Ho—O distance of 2.390 Å, while the Li atom is located inside an irregular tetrahedron with a mean Li—O distance of 1.980 Å. All these bond lengths are conform with those mentioned in the literature (International Tables for X-Ray Crystallography, 1968; Durif, 1995; Amami et al., 2004).

By sharing edges, the HoO8 and LiO4 polyhedra are joined to produce infinite linear chains running along the b axis (Fig. 1), in contrast to crystal structure of NaHo(PO3)4 (form II) (Amami et al., 2004) where zigzag chains of face-sharing HoO8 and NaO8 polyhedra are observed. As shown in Fig. 2, each chain shares corners of its polyhedra with four adjacent polyphosphate chains.

It is noteworthy that no O atom is common to two Ho atoms, and the closest Ho···Ho distance of 5.570 (1) Å in LiHo(PO3)4 is comparable with that found in HoP5O14 (Tranqui et al., 1972). Bond-valence-sum values (Brown & Altermatt, 1985) are 0.998, 3.054, 4.936 and 4.967 valence units for Li, Ho, P1 and P2, respectively, in good agreement with the expected formal charges.

Related literature top

For isotypic LiLn(PO3)4 structures, see: Ben Zarkouna & Driss (2004) for Ln = Yb; Ben Zarkouna et al. (2005) for Ln = Er; Ben Zarkouna et al. (2007) for Ln = Tb. For related structures, see: Amami et al. (2004) (NaHo(PO3)4); Palkina et al. (1976) (β-KHo(PO3)4); Tranqui et al. (1972) (HoP5O14). For general background, see: Brown & Altermatt (1985); Durif (1995); Liu et al. (1999); Palkina et al. (1981); International Tables for X-Ray Crystallography (1968).

Experimental top

The title compound was prepared in single crystalline form using the flux method. At room temperature, 3 g of Li2CO3 and 0.5 g of Ho2O3 were slowly added to 10 ml of H3PO4 (85%wt) in a glassy carbon crucible. The resulting mixture was then progressively heated to 573 K and kept at this temperature for 8 days. After cooling to room temperature and removal of the excess phosphoric flux with boiling water, pale yellow crystals of LiHo(PO3)4 were separated.

Refinement top

The highest peak is located 0.87 Å from Ho and the deepest hole is located 1.00 Å from the same atom.

Computing details top

Data collection: CAD-4 EXPRESS (Duisenberg, 1992; Macíček & Yordanov, 1992); cell refinement: CAD-4 EXPRESS (Duisenberg, 1992; Macíček & Yordanov, 1992); data reduction: XCAD4 (Harms & Wocadlo, 1995); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 1998); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures top
[Figure 1] Fig. 1. : Alternating arrangement of HoO8 and LiO4 polyhedra projected along the a axis. PO4 tetrahedra are omitted for clarity.
[Figure 2] Fig. 2. : Projection of the LiHo(PO3)4 structure along the b axis.
Lithium holmium(III) polyphosphate(V) top
Crystal data top
LiHo(PO3)4F(000) = 904
Mr = 487.75Dx = 3.654 Mg m3
Monoclinic, C2/cMo Kα radiation, λ = 0.71069 Å
Hall symbol: -C 2ycCell parameters from 25 reflections
a = 16.280 (3) Åθ = 10.1–14.7°
b = 7.039 (2) ŵ = 9.72 mm1
c = 9.561 (2) ÅT = 293 K
β = 125.99 (2)°Plate, pale yellow
V = 886.5 (4) Å30.31 × 0.14 × 0.07 mm
Z = 4
Data collection top
Enraf–Nonius CAD-4
diffractometer
1076 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.016
Graphite monochromatorθmax = 28.0°, θmin = 3.1°
ω/2θ scansh = 2117
Absorption correction: ψ scan
(North et al., 1968)
k = 29
Tmin = 0.095, Tmax = 0.378l = 012
1500 measured reflections2 standard reflections every 120 min
1078 independent reflections intensity decay: none
Refinement top
Refinement on F2Primary atom site location: heavy method
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.025 w = 1/[σ2(Fo2) + (0.0459P)2 + 12.7265P]
where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.071(Δ/σ)max < 0.001
S = 1.12Δρmax = 2.75 e Å3
1078 reflectionsΔρmin = 3.18 e Å3
84 parametersExtinction correction: SHELXL97 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
0 restraintsExtinction coefficient: 0.0014 (3)
Crystal data top
LiHo(PO3)4V = 886.5 (4) Å3
Mr = 487.75Z = 4
Monoclinic, C2/cMo Kα radiation
a = 16.280 (3) ŵ = 9.72 mm1
b = 7.039 (2) ÅT = 293 K
c = 9.561 (2) Å0.31 × 0.14 × 0.07 mm
β = 125.99 (2)°
Data collection top
Enraf–Nonius CAD-4
diffractometer
1076 reflections with I > 2σ(I)
Absorption correction: ψ scan
(North et al., 1968)
Rint = 0.016
Tmin = 0.095, Tmax = 0.3782 standard reflections every 120 min
1500 measured reflections intensity decay: none
1078 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0250 restraints
wR(F2) = 0.071 w = 1/[σ2(Fo2) + (0.0459P)2 + 12.7265P]
where P = (Fo2 + 2Fc2)/3
S = 1.12Δρmax = 2.75 e Å3
1078 reflectionsΔρmin = 3.18 e Å3
84 parameters
Special details top

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 (Å2) top
xyzUiso*/Ueq
Li0.00000.708 (2)0.25000.015 (3)
Ho0.00000.20312 (4)0.25000.0073 (1)
P10.13774 (8)0.5517 (2)0.6157 (1)0.0067 (2)
P20.14654 (8)0.1504 (2)0.6961 (1)0.0068 (2)
O10.1137 (3)0.7154 (5)0.6843 (5)0.0118 (7)
O20.0711 (3)0.0845 (5)0.7255 (5)0.0116 (6)
O30.1280 (3)0.1150 (5)0.5262 (4)0.0121 (7)
O40.1568 (3)0.3740 (5)0.7337 (4)0.0107 (6)
O50.2552 (2)0.0776 (5)0.8526 (4)0.0105 (6)
O60.0652 (2)0.5022 (5)0.4280 (4)0.0104 (6)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Li0.018 (6)0.011 (6)0.020 (7)0.0000.012 (6)0.000
Ho0.0063 (2)0.0076 (2)0.0071 (2)0.0000.0034 (1)0.000
P10.0052 (5)0.0069 (5)0.0072 (5)0.0002 (4)0.0031 (4)0.0001 (4)
P20.0051 (5)0.0072 (5)0.0073 (5)0.0001 (4)0.0032 (4)0.0009 (4)
O10.012 (2)0.009 (2)0.016 (2)0.001 (1)0.009 (1)0.002 (1)
O20.008 (1)0.012 (2)0.016 (2)0.001 (1)0.008 (1)0.002 (1)
O30.012 (2)0.014 (2)0.008 (1)0.002 (1)0.004 (1)0.000 (1)
O40.015 (2)0.007 (1)0.009 (1)0.001 (1)0.007 (1)0.002 (1)
O50.005 (1)0.016 (2)0.010 (1)0.002 (1)0.005 (1)0.002 (1)
O60.007 (1)0.014 (2)0.006 (1)0.001 (1)0.001 (1)0.000 (1)
Geometric parameters (Å, º) top
Li—O2i1.962 (9)Ho—O62.516 (3)
Li—O2ii1.962 (9)Ho—O6iii2.516 (3)
Li—O6iii1.999 (9)P1—O11.488 (4)
Li—O61.999 (9)P1—O61.499 (3)
Ho—O3iii2.287 (3)P1—O41.589 (4)
Ho—O32.287 (3)P1—O5vi1.594 (3)
Ho—O1ii2.348 (4)P2—O21.486 (3)
Ho—O1i2.348 (4)P2—O31.488 (3)
Ho—O2iv2.411 (3)P2—O51.588 (3)
Ho—O2v2.411 (3)P2—O41.601 (4)
O2i—Li—O2ii83.7 (5)O6—P1—O5vi105.0 (2)
O2i—Li—O6iii119.57 (14)O4—P1—O5vi102.7 (2)
O2ii—Li—O6iii125.85 (14)O2—P2—O3119.6 (2)
O2i—Li—O6125.85 (14)O2—P2—O5107.9 (2)
O2ii—Li—O6119.57 (14)O3—P2—O5111.9 (2)
O6iii—Li—O687.2 (5)O2—P2—O4104.6 (2)
O1—P1—O6118.8 (2)O3—P2—O4109.7 (2)
O1—P1—O4106.8 (2)O5—P2—O4101.2 (2)
O6—P1—O4110.8 (2)P1—O4—P2131.6 (2)
O1—P1—O5vi111.7 (2)P2—O5—P1vii134.8 (2)
Symmetry codes: (i) x, y+1, z1/2; (ii) x, y+1, z+1; (iii) x, y, z+1/2; (iv) x, y, z+1; (v) x, y, z1/2; (vi) x+1/2, y+1/2, z+3/2; (vii) x+1/2, y1/2, z+3/2.

Experimental details

Crystal data
Chemical formulaLiHo(PO3)4
Mr487.75
Crystal system, space groupMonoclinic, C2/c
Temperature (K)293
a, b, c (Å)16.280 (3), 7.039 (2), 9.561 (2)
β (°) 125.99 (2)
V3)886.5 (4)
Z4
Radiation typeMo Kα
µ (mm1)9.72
Crystal size (mm)0.31 × 0.14 × 0.07
Data collection
DiffractometerEnraf–Nonius CAD-4
diffractometer
Absorption correctionψ scan
(North et al., 1968)
Tmin, Tmax0.095, 0.378
No. of measured, independent and
observed [I > 2σ(I)] reflections
1500, 1078, 1076
Rint0.016
(sin θ/λ)max1)0.660
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.025, 0.071, 1.12
No. of reflections1078
No. of parameters84
w = 1/[σ2(Fo2) + (0.0459P)2 + 12.7265P]
where P = (Fo2 + 2Fc2)/3
Δρmax, Δρmin (e Å3)2.75, 3.18

Computer programs: CAD-4 EXPRESS (Duisenberg, 1992; Macíček & Yordanov, 1992), XCAD4 (Harms & Wocadlo, 1995), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), DIAMOND (Brandenburg, 1998).

Selected bond lengths (Å) top
Li—O2i1.962 (9)P1—O61.499 (3)
Li—O61.999 (9)P1—O41.589 (4)
Ho—O32.287 (3)P1—O5iii1.594 (3)
Ho—O1i2.348 (4)P2—O21.486 (3)
Ho—O2ii2.411 (3)P2—O31.488 (3)
Ho—O62.516 (3)P2—O51.588 (3)
P1—O11.488 (4)P2—O41.601 (4)
Symmetry codes: (i) x, y+1, z1/2; (ii) x, y, z1/2; (iii) x+1/2, y+1/2, z+3/2.
 

References

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First citationBen Zarkouna, E. & Driss, A. (2004). Acta Cryst. E60, i102–i104.  Web of Science CrossRef IUCr Journals Google Scholar
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First citationPalkina, K. K., Kuznetsov, V. G., Chudinova, N. N. & Chibiskova, N. T. (1976). Izv. Akad. Nauk SSSR Neorg. Mater. 12, 730–734.  CAS Google Scholar
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First citationTranqui, D., Bagieu-Beucher, M. & Durif, A. (1972). Bull. Soc. Fr. Minéral. Cryst. 95, 437–440.  Google Scholar

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