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

Journal logoCRYSTALLOGRAPHIC
COMMUNICATIONS
ISSN: 2056-9890

Disordered LiZnVO4 with a phenacite structure

aEquipe Sciences des Matériaux, Faculté des Sciences et Techniques Errachidia, Morocco, bLaboratoire d'Elaboration, Analyse Chimique et Ingénierie, Département de Chimie, Université de La Rochelle, Avenue Marillac, 17042 La Rochelle Cedex 01, France, and cLaboratoire de Chimie du Solide Appliquée, Faculté des Sciences, Université Mohammed V-Agdal, Avenue Ibn Battouta, BP 1014, Rabat, Morocco
*Correspondence e-mail: med.azrour@gmail.com

(Received 27 March 2010; accepted 10 April 2010; online 17 April 2010)

Single crystals of lithium zinc vanadate, LiZnVO4, were grown by the flux method. The structural type of this vanadate is characterized by a three-dimensional arrangement of tetra­hedra sharing apices in an LiZnVO4 network. This arrangement contains three different tetra­hedra, namely one [VO4] and two disordered mixed-site [Li/ZnO4] tetra­hedra. The resulting lattice gives rise to hexa­gonal channels running along the [0001] direction. Both sites in the mixed-site [Li/ZnO4] tetra­hedra are occupied by a statistical mixture of lithium and zinc with a 1:1 ratio. Therefore, LiZnVO4 appears to be the first vanadate known to crystallize with a disordered phenacite structure. Moreover, the resulting values of calculated bond valences (Li = 1.083, Zn = 2.062 and V = 5.185) tend to confirm the structural model.

Related literature

For related structural studies, see: Hartmann (1989[Hartmann, P. (1989). Z. Kristallogr. 187, 139-143.]); Capsoni et al. (2006[Capsoni, D., Bini, M., Massarotti, V., Mustarelli, P., Belotti, F. & Galinetto, P. (2006). J. Phys. Chem. B, 110, 5409-5415.]); Zachariasen (1971[Zachariasen, W. H. (1971). Kristallografiya, 16, 1161-1166.]). For compounds with the same structural type, see: Bu et al. (1996[Bu, X., Gier, T. E. & Stucky, G. D. (1996). Acta Cryst. C52, 1601-1603.]); Elammari & Elouadi (1989[Elammari, L. & Elouadi, B. (1989). Acta Cryst. C45, 1864-1867.]); Elouadi & Elammari (1990[Elouadi, B. & Elammari, L. (1990). Ferroelectrics, 107, 253-258.]); Jensen et al. (1998[Jensen, T. R., Norby, P., Hanson, J. C., Simonsen, O., Skou, E. M., Stein, P. C. & Boye, H. A. (1998). J. Mater. Chem. 8, 969-975.]). For bond-valence calculations, see: Brown & Altermatt (1985[Brown, I. D. & Altermatt, D. (1985). Acta Cryst. B41, 244-247.]).

Experimental

Crystal data
  • LiZnVO4

  • Mr = 187.25

  • Trigonal, [R \overline 3]

  • a = 14.107 (3) Å

  • c = 9.441 (2) Å

  • V = 1627.1 (6) Å3

  • Z = 18

  • Mo Kα radiation

  • μ = 9.06 mm−1

  • T = 298 K

  • 0.14 × 0.12 × 0.10 mm

Data collection
  • Bruker X8 APEXII CCD area-detector diffractometer

  • Absorption correction: multi-scan (SADABS; Sheldrick, 2003[Sheldrick, G. M. (2003). SADABS. University of Göttingen, Germany.]) Tmin = 0.292, Tmax = 0.404

  • 9709 measured reflections

  • 1622 independent reflections

  • 1213 reflections with I > 2σ(I)

  • Rint = 0.070

Refinement
  • R[F2 > 2σ(F2)] = 0.024

  • wR(F2) = 0.055

  • S = 1.04

  • 1622 reflections

  • 69 parameters

  • Δρmax = 0.51 e Å−3

  • Δρmin = −0.53 e Å−3

Data collection: APEX2 (Bruker, 2005[Bruker (2005). APEX2 and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.]); cell refinement: SAINT (Bruker, 2005[Bruker (2005). APEX2 and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.]); data reduction: SAINT; 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: ORTEP-3 for Windows (Farrugia, 1997[Farrugia, L. J. (1997). J. Appl. Cryst. 30, 565.]) and PLATON (Spek, 2009[Spek, A. L. (2009). Acta Cryst. D65, 148-155.]); software used to prepare material for publication: WinGX (Farrugia, 1999[Farrugia, L. J. (1999). J. Appl. Cryst. 32, 837-838.]).

Supporting information


Comment top

Our particular interest here is to investigate the form nature of the crystallized phase and determine the structural type that could result from the association of small size cations likely to enter under normal conditions of pressure and temperature, tetrahedral cavities of oxides like in phenacite Be2SiO4 network (Hartmann, 1989; Zachariasen, 1971). The compounds currently known to crystallize with such structural type are LiZnPO4 (Bu et al., 1996; Elammari & Elouadi, 1989; Elouadi & Elammari, 1990) and LiZnAsO4 (Jensen et al., 1998).

The structural type of the title compound, related to the phenacite structure, could be described (Fig.1) as three dimensional arrangement of [MO4] tetrahedra ( M= Li/Zn or V) sharing apices. The arrangement concerns three different types of tetrahedra [VO4] and two disordered sites [Li/ZnO4] which give rise to an overall disordered phenacite structure. When viewed along the c axis, the packing of [MO4] tetraherdra results in two types of tunnels: large hexagonal tunnels surrounded by six lozenge like channels (rings of four tetrahedra). Similar description has recently been reported by Capsoni et al. (2006) using a powder x-ray diffraction data of LiZnVO4. However, a careful observation of the two models can highlights the difference between our two results. Indeed, in addition to the difference of the lengths of chemical bonds, the occupancy rate of cationic Wycoff sites is different. Thus, in our model, there is only a disorder between Li and Zn with a statistical distribution of both ions on the two crystallographic sites, while the third site is only occupied by vanadium cation. Furthermore, A bond-valence analysis (Li <1.083>, Zn<2.062> and <V<5.185>) based on the empirical formula proposed by Brown & Altermatt (1985) is in favor of this model . The cationic disorder mentioned by Capsoni et al. could be seen as due to preparation methods. The powder used was slowly cooled from 853 K after 24 h sintering. Whereas, the growth of our crystal, from a flux melted at 1073 k and slowly cooled with a rate of 5 K h-1. Thus the resulting sintering of our crystal was much longer. A more ordred system is then to be expected.

When such structural type is seen as a close packing of oxygen anions, it appears as a lacunar hexagonal close packing of O2- ions. Fig.2 shows a typical oxygen layer and the elevation of such oxygen plans as successively stacked ( ABAB···) along [0001]. The coordination sphere of all cations is of tetrahedral type. The analysis of oxygen environment shows a regular triangular cavity for O2- anions with an average edge length of <V—Li/Zn> = 3.240 Å.

In the case of the present form of LiZnVO4, the disordered phenacite structure was attributed to the existence of a mixed tetrahedral site [Li/ZnO4] occupied by both Li and Zn. The resulting space group is R-3. LiZnVO4 is probably the first vanadate known to crystallize with a disordered phenacite structure.

Related literature top

For related structural studies, see: Hartmann (1989); Capsoni et al. (2006); Zachariasen (1971). For compounds with the same structural type, see: Bu et al.(1996); Elammari & Elouadi (1989); Elouadi & Elammari (1990); Jensen et al. (1998). For bond-valence calculations, see: Brown & Altermatt (1985).

Experimental top

Prior to the crystal growth, pulverulent samples of the compound LiZnVO4 and the flux LiVO3 are synthesized by the regular solid state reaction according to the following reactions:

Li2CO3 + 2ZnO + V2O5 —> 2LiZnVO4 + CO2 Li2CO3 + V2O5 —> 2LiVO3 + CO2

Single crystal of the monovanadate LiZnVO4 were grown from a bath of equimolar mixture of freohly prepared powders of LiZnVO4 and LiVO3. The starting mixture was thoroughly ground before to be melted at 1073 K in a platinum crucible and slowly cooled with a rate of 5 K h-1 to 773 K. The furnace was then switched off and the whole system naturally cooled down to room temperature. Single crystal s were collected from the crucible after dissolwing the flux in warmed water.

Structure description top

Our particular interest here is to investigate the form nature of the crystallized phase and determine the structural type that could result from the association of small size cations likely to enter under normal conditions of pressure and temperature, tetrahedral cavities of oxides like in phenacite Be2SiO4 network (Hartmann, 1989; Zachariasen, 1971). The compounds currently known to crystallize with such structural type are LiZnPO4 (Bu et al., 1996; Elammari & Elouadi, 1989; Elouadi & Elammari, 1990) and LiZnAsO4 (Jensen et al., 1998).

The structural type of the title compound, related to the phenacite structure, could be described (Fig.1) as three dimensional arrangement of [MO4] tetrahedra ( M= Li/Zn or V) sharing apices. The arrangement concerns three different types of tetrahedra [VO4] and two disordered sites [Li/ZnO4] which give rise to an overall disordered phenacite structure. When viewed along the c axis, the packing of [MO4] tetraherdra results in two types of tunnels: large hexagonal tunnels surrounded by six lozenge like channels (rings of four tetrahedra). Similar description has recently been reported by Capsoni et al. (2006) using a powder x-ray diffraction data of LiZnVO4. However, a careful observation of the two models can highlights the difference between our two results. Indeed, in addition to the difference of the lengths of chemical bonds, the occupancy rate of cationic Wycoff sites is different. Thus, in our model, there is only a disorder between Li and Zn with a statistical distribution of both ions on the two crystallographic sites, while the third site is only occupied by vanadium cation. Furthermore, A bond-valence analysis (Li <1.083>, Zn<2.062> and <V<5.185>) based on the empirical formula proposed by Brown & Altermatt (1985) is in favor of this model . The cationic disorder mentioned by Capsoni et al. could be seen as due to preparation methods. The powder used was slowly cooled from 853 K after 24 h sintering. Whereas, the growth of our crystal, from a flux melted at 1073 k and slowly cooled with a rate of 5 K h-1. Thus the resulting sintering of our crystal was much longer. A more ordred system is then to be expected.

When such structural type is seen as a close packing of oxygen anions, it appears as a lacunar hexagonal close packing of O2- ions. Fig.2 shows a typical oxygen layer and the elevation of such oxygen plans as successively stacked ( ABAB···) along [0001]. The coordination sphere of all cations is of tetrahedral type. The analysis of oxygen environment shows a regular triangular cavity for O2- anions with an average edge length of <V—Li/Zn> = 3.240 Å.

In the case of the present form of LiZnVO4, the disordered phenacite structure was attributed to the existence of a mixed tetrahedral site [Li/ZnO4] occupied by both Li and Zn. The resulting space group is R-3. LiZnVO4 is probably the first vanadate known to crystallize with a disordered phenacite structure.

For related structural studies, see: Hartmann (1989); Capsoni et al. (2006); Zachariasen (1971). For compounds with the same structural type, see: Bu et al.(1996); Elammari & Elouadi (1989); Elouadi & Elammari (1990); Jensen et al. (1998). For bond-valence calculations, see: Brown & Altermatt (1985).

Computing details top

Data collection: APEX2 (Bruker, 2005); cell refinement: SAINT (Bruker, 2005); data reduction: SAINT (Bruker, 2005); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia,1997) and PLATON (Spek, 2009); software used to prepare material for publication: WinGX (Farrugia, 1999).

Figures top
[Figure 1] Fig. 1. : A three-dimensional view of LiZnVO4 crystal structure, showing tunnels runnig along the c axis.
[Figure 2] Fig. 2. : Partial projection of the crystal structure on (0 0 1), showing lacunar hexagonal close packing of O2- ions.
lithium zinc vanadate top
Crystal data top
LiZnVO4Dx = 3.440 Mg m3
Mr = 187.25Mo Kα radiation, λ = 0.71073 Å
Trigonal, R3Cell parameters from 9709 reflections
Hall symbol: -R 3θ = 10–30°
a = 14.107 (3) ŵ = 9.06 mm1
c = 9.441 (2) ÅT = 298 K
V = 1627.1 (6) Å3Prism, pale yellow
Z = 180.14 × 0.12 × 0.10 mm
F(000) = 1584
Data collection top
Bruker X8 APEXII CCD area-detector
diffractometer
1622 independent reflections
Radiation source: fine-focus sealed tube1213 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.070
φ and ω scansθmax = 35.2°, θmin = 4.0°
Absorption correction: multi-scan
(SADABS; Sheldrick, 2003)
h = 2222
Tmin = 0.292, Tmax = 0.404k = 2222
9709 measured reflectionsl = 1515
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.024 w = 1/[σ2(Fo2) + (0.0124P)2 + 2.5069P]
where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.055(Δ/σ)max = 0.001
S = 1.04Δρmax = 0.51 e Å3
1622 reflectionsΔρmin = 0.53 e Å3
69 parametersExtinction correction: SHELXL97 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
0 restraintsExtinction coefficient: 0.0088 (2)
Crystal data top
LiZnVO4Z = 18
Mr = 187.25Mo Kα radiation
Trigonal, R3µ = 9.06 mm1
a = 14.107 (3) ÅT = 298 K
c = 9.441 (2) Å0.14 × 0.12 × 0.10 mm
V = 1627.1 (6) Å3
Data collection top
Bruker X8 APEXII CCD area-detector
diffractometer
1622 independent reflections
Absorption correction: multi-scan
(SADABS; Sheldrick, 2003)
1213 reflections with I > 2σ(I)
Tmin = 0.292, Tmax = 0.404Rint = 0.070
9709 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.02469 parameters
wR(F2) = 0.0550 restraints
S = 1.04Δρmax = 0.51 e Å3
1622 reflectionsΔρmin = 0.53 e Å3
Special details top

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Refinement. Refinement on F2 for ALL reflections except for 0 with very negative F2 or flagged by the user for potential systematic errors. Weighted R-factors wR and all goodnesses of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The observed criterion of F2 > σ(F2) is used only for calculating -R-factor-obs 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*/UeqOcc. (<1)
V10.454581 (17)0.138171 (16)0.08352 (2)0.00790 (7)
Zn10.45273 (2)0.14015 (2)0.24915 (3)0.01132 (7)0.50
Li10.45273 (2)0.14015 (2)0.24915 (3)0.01132 (7)0.50
Zn20.64622 (2)0.12175 (3)0.24882 (3)0.01150 (7)0.50
Li20.64622 (2)0.12175 (3)0.24882 (3)0.01150 (7)0.50
O10.34102 (7)0.01142 (7)0.08427 (11)0.01335 (17)
O20.56475 (8)0.11882 (9)0.08215 (10)0.01353 (17)
O30.45578 (8)0.20780 (8)0.06565 (10)0.01419 (18)
O40.45936 (8)0.20728 (8)0.23409 (10)0.01377 (17)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
V10.00918 (10)0.00812 (10)0.00692 (9)0.00472 (8)0.00012 (6)0.00004 (6)
Zn10.01190 (12)0.01217 (13)0.01038 (12)0.00637 (10)0.00052 (9)0.00069 (9)
Li10.01190 (12)0.01217 (13)0.01038 (12)0.00637 (10)0.00052 (9)0.00069 (9)
Zn20.01159 (13)0.01368 (13)0.01016 (12)0.00701 (10)0.00005 (9)0.00037 (9)
Li20.01159 (13)0.01368 (13)0.01016 (12)0.00701 (10)0.00005 (9)0.00037 (9)
O10.0109 (4)0.0102 (4)0.0180 (4)0.0046 (3)0.0010 (3)0.0000 (3)
O20.0121 (4)0.0198 (4)0.0115 (3)0.0101 (3)0.0005 (3)0.0005 (3)
O30.0219 (5)0.0120 (4)0.0103 (3)0.0096 (3)0.0007 (3)0.0009 (3)
O40.0209 (4)0.0125 (4)0.0104 (4)0.0102 (4)0.0003 (3)0.0004 (3)
Geometric parameters (Å, º) top
V1—O11.7027 (10)Zn2—O21.9368 (10)
V1—O41.7059 (10)Zn2—O4x1.9495 (10)
V1—O21.7071 (10)Zn2—O4xi1.9676 (11)
V1—O31.7123 (10)Zn2—Li1iv3.1441 (8)
V1—Li2i3.1568 (7)Zn2—Zn1iv3.1441 (8)
V1—Li1ii3.1719 (8)Zn2—Li1viii3.2314 (8)
V1—Li2iii3.2409 (8)Zn2—Li2i3.2675 (7)
V1—Li1iv3.2523 (6)Zn2—Li2x3.2676 (7)
V1—Li2v3.2978 (7)O1—Li2iii1.9294 (11)
V1—Li1vi3.3232 (7)O1—Zn2iii1.9294 (11)
Zn1—O2vi1.9410 (10)O1—Zn1ii1.9442 (11)
Zn1—O1vii1.9441 (11)O1—Li1ii1.9442 (11)
Zn1—O3iv1.9588 (11)O2—Li1iv1.9411 (10)
Zn1—O31.9679 (11)O2—Zn1iv1.9411 (10)
Zn1—Zn2vi3.1441 (8)O3—Li1vi1.9587 (11)
Zn1—Li2vi3.1441 (8)O3—Zn1vi1.9587 (11)
Zn1—Li2viii3.2314 (8)O4—Li2i1.9496 (10)
Zn1—Li1vi3.2765 (7)O4—Zn2i1.9496 (10)
Zn1—Li1iv3.2766 (7)O4—Li2v1.9676 (11)
Zn2—O1ix1.9294 (11)O4—Zn2v1.9676 (11)
O1—V1—O4110.14 (5)O2vi—Zn1—O3115.71 (4)
O1—V1—O2106.61 (5)O1vii—Zn1—O3106.57 (4)
O4—V1—O2108.58 (5)O3iv—Zn1—O3110.08 (5)
O1—V1—O3109.88 (5)O1ix—Zn2—O2111.98 (5)
O4—V1—O3111.80 (5)O1ix—Zn2—O4x108.76 (4)
O2—V1—O3109.69 (5)O2—Zn2—O4x117.26 (4)
O2vi—Zn1—O1vii109.39 (5)O1ix—Zn2—O4xi102.55 (4)
O2vi—Zn1—O3iv106.12 (4)O2—Zn2—O4xi107.30 (4)
O1vii—Zn1—O3iv108.84 (4)O4x—Zn2—O4xi107.87 (5)
Symmetry codes: (i) y+1/3, x+y+2/3, z+2/3; (ii) x+y+2/3, x+1/3, z+1/3; (iii) xy1/3, x2/3, z+1/3; (iv) xy+1/3, x1/3, z1/3; (v) x+y+1, x+1, z; (vi) y+1/3, x+y+2/3, z1/3; (vii) y+1/3, xy1/3, z1/3; (viii) x+1, y, z; (ix) y+2/3, x+y+1/3, z+1/3; (x) xy+1/3, x1/3, z+2/3; (xi) y+1, xy, z.

Experimental details

Crystal data
Chemical formulaLiZnVO4
Mr187.25
Crystal system, space groupTrigonal, R3
Temperature (K)298
a, c (Å)14.107 (3), 9.441 (2)
V3)1627.1 (6)
Z18
Radiation typeMo Kα
µ (mm1)9.06
Crystal size (mm)0.14 × 0.12 × 0.10
Data collection
DiffractometerBruker X8 APEXII CCD area-detector
Absorption correctionMulti-scan
(SADABS; Sheldrick, 2003)
Tmin, Tmax0.292, 0.404
No. of measured, independent and
observed [I > 2σ(I)] reflections
9709, 1622, 1213
Rint0.070
(sin θ/λ)max1)0.812
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.024, 0.055, 1.04
No. of reflections1622
No. of parameters69
Δρmax, Δρmin (e Å3)0.51, 0.53

Computer programs: APEX2 (Bruker, 2005), SAINT (Bruker, 2005), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), ORTEP-3 for Windows (Farrugia,1997) and PLATON (Spek, 2009), WinGX (Farrugia, 1999).

 

Acknowledgements

The authors thanks the Unit of Support for Technical and Scientific Research (UATRS, CNRST) for the X-ray measurements.

References

First citationBrown, I. D. & Altermatt, D. (1985). Acta Cryst. B41, 244–247.  CrossRef CAS Web of Science IUCr Journals Google Scholar
First citationBruker (2005). APEX2 and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.  Google Scholar
First citationBu, X., Gier, T. E. & Stucky, G. D. (1996). Acta Cryst. C52, 1601–1603.  CrossRef CAS Web of Science IUCr Journals Google Scholar
First citationCapsoni, D., Bini, M., Massarotti, V., Mustarelli, P., Belotti, F. & Galinetto, P. (2006). J. Phys. Chem. B, 110, 5409–5415.  Web of Science CrossRef PubMed CAS Google Scholar
First citationElammari, L. & Elouadi, B. (1989). Acta Cryst. C45, 1864–1867.  CrossRef CAS Web of Science IUCr Journals Google Scholar
First citationElouadi, B. & Elammari, L. (1990). Ferroelectrics, 107, 253–258.  CrossRef CAS Google Scholar
First citationFarrugia, L. J. (1997). J. Appl. Cryst. 30, 565.  CrossRef IUCr Journals Google Scholar
First citationFarrugia, L. J. (1999). J. Appl. Cryst. 32, 837–838.  CrossRef CAS IUCr Journals Google Scholar
First citationHartmann, P. (1989). Z. Kristallogr. 187, 139–143.  Google Scholar
First citationJensen, T. R., Norby, P., Hanson, J. C., Simonsen, O., Skou, E. M., Stein, P. C. & Boye, H. A. (1998). J. Mater. Chem. 8, 969–975.  Web of Science CrossRef CAS Google Scholar
First citationSheldrick, G. M. (2003). SADABS. University of Göttingen, Germany.  Google Scholar
First citationSheldrick, G. M. (2008). Acta Cryst. A64, 112–122.  Web of Science CrossRef CAS IUCr Journals Google Scholar
First citationSpek, A. L. (2009). Acta Cryst. D65, 148–155.  Web of Science CrossRef CAS IUCr Journals Google Scholar
First citationZachariasen, W. H. (1971). Kristallografiya, 16, 1161–1166.  CAS Google Scholar

This is an open-access article distributed under the terms of the Creative Commons Attribution (CC-BY) Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.

Journal logoCRYSTALLOGRAPHIC
COMMUNICATIONS
ISSN: 2056-9890
Follow Acta Cryst. E
Sign up for e-alerts
Follow Acta Cryst. on Twitter
Follow us on facebook
Sign up for RSS feeds