supplementary materials


Acta Cryst. (2013). E69, i34    [ doi:10.1107/S1600536813012427 ]

Synchrotron powder study of Na3V(PO3)3N

M. Kim and S.-J. Kim

Abstract top

Polycrystalline trisodium vanadium(III) nitridotriphosphate, Na3V(PO3)3N, was prepared by thermal nitridation of a mixture of NaPO3 and V2O5. The title compound is isotypic with Na3Al(PO3)3N. In the crystal, the P-atom and the three O-atom sites are on general positions, whereas the Na-, V- and N-atom sites are located on threefold rotation axes. The P atom is coordinated by three O atoms and one N atom in form of a slightly distorted tetrahedron. Three PO3N tetrahedra build up a nitridotriphosphate group, (PO3)3N, by sharing a common N atom. The V atom is coordinated by six O atoms in form of a slightly distorted octahedron. The Na+ ions occupy three crystallographically distinct sites. One Na+ ion is situated in an irregular polyhedral coordination environment composed of six O atoms and one N atom, while the other two Na+ cations are surrounded by six and nine O atoms, respectively.

Comment top

There has been growing interest in the area of mixed anionic systems for exploration of new functional materials. Synthesis in the area of mixed anionic systems allows for the tuning of numerous properties, including energy storage, photocatalytic, and dielectric properties. More than two decades ago, the synthesis of several isotypic compounds with the chemical formulae of A3B(PO3)3N (A = Na, K; B = Al, Ga, Cr, Mn, Fe) and A2B2(PO3)3N (A = Na; B = Mg, Mn, Fe, Co) by versatile nitridation reactions have been reported (Conanec et al., 1996; Feldmann, 1987a,b; Marchand & Laurent, 1991, Marchand et al., 2000) The crystal structure of Na3Al(PO3)3N has been determined by X-ray diffraction from a single-crystal (Conanec et al., 1994). For the other compounds, however, no information except their unit cell parameters are known. In this work, we report the synthesis of the new nitridophosphate compound, Na3V(PO3)3N, and its crystal structure refined on baisi of the Rietveld method from synchrotron powder X-ray diffraction data.

The crystal structure of Na3V(PO3)3N is isotypic with that of Na3Al(PO3)3N (Conanec et al., 1994). The lattice parameter of Na3V(PO3)3N (a = 9.44783 (5) Å) is slighty larger than that of Na3Al(PO3)3N (a = 9.274 (1) Å), which is attributed to the different sizes of the V(III) and Al(III) ions. In this structure, the P and the three O atoms lie on general positions (12b) while the other atoms lie on special positions related to threefold rotation axes (4a).

The P atom is coordinated by three O atoms and one N atom to form a PO3N tetrahedron. The (PO3)3N entity is formed by three PO3N tetrahedra sharing the corner occupied by the nitrogen atom (Fig. 1). The range of P—O bond lengths (1.538 (6) - 1.541 (6) Å) in Na3V(PO3)3N is close to that found in compositionally related compounds such as Na3Al(PO3)3N (~1.50 - 1.53 Å); Na2Mg2(PO3)3N (~1.53 - 1.55 Å); Na3V2(PO4)3 (~1.52 1.54 Å) (Conanec et al., 1994; Lee et al., 2012; Zatovsky, 2010). The P—N bond length (1.738 (7) Å) is similar to those observed for tricoordinating nitrogen atoms in nitrido-compounds such as K3P6N11 (1.71 Å) (Jacobs & Nymwegen, 1997). Na, V and N atoms are arranged along the [111] direction in the sequence of Na2—V—Na3—Na1—N—Na2—V-··· (Fig. 2). The V atom is connected to six oxygen atoms located at the vertices of PO3N tetrahedra, forming a slightly distorted octahedron. The average V—O distance is 2.005 (11) Å which is close to the sum of the ionic radii (2.02 Å) of V3+ and O2- (Shannon, 1976). The Na atoms occupy three crystallographically distinct sites. Na1 is coordinated to six O atoms (mean Na—O is 2.58 Å) and one N atom (Na—N is 2.947 (7) Å) to form an irregular NaO6N polyhedron. Na2 and Na3 are 6- and 9-coordinated, respectively, within distorted polyhedra elongated along the threefold axis. The bond valence sums (Brese & O'Keeffe, 1991) calculated from the bond lengths (valence units; Na1: 0.80, Na2: 1.29, Na3: 0.96, V: 2.96, P: 4.61, O1: 1.90, O2: 1.92, O3: 1.85, N: 2.80) are close to the expected valence states of respective atoms.

Related literature top

For structure determinations of isotypic Na3Al(PO3)3N, see: Conanec et al. (1994). For the preparation of various related materials, A3B(PO3)3N (A = Na, K; B = Al, Ga, Cr, Mn, Fe) and A2B2(PO3)3N (A = Na; B = Mg, Mn, Fe, Co), see: Conanec et al. (1996); Feldmann (1987a,b). For studies focused on the ionic conductivity of Na2Mg2(PO3)3N, see: Lee et al. (2012). For a review of structural features of metal nitridophosphate compounds, see: Marchand & Laurent (1991); Marchand et al. (2000). For bond-valence-sum calculations, see: Brese & O'Keeffe (1991). For comparison bond lengths in related structures, see: Conanec et al. (1994); Jacobs & Nymwegen (1997); Lee et al. (2012); Shannon (1976); Zatovsky (2010).

Experimental top

An appropriate amount of NaPO3 and V2O5 was mixed thoroughly in an agate mortar and placed in an alumina crucible. The mixture was initially heated at 523 K for 6 h. The product was reground and heated again at 973 K for 8 h and furnace-cooled to room temperature. All the heat treatments were carried out in continuous flowing anhydrous ammonia gas (flow rate = 30 ml/min) in a tube furnace. The resultant powder sample was characterized by synchrotron X-ray diffraction (sXRD). The measurement was performed on beamline 9B-HRPD at Pohang Accelerator Laboratory, Pohang, Korea. The incident X-rays were vertically collimated by a mirror, and monochromated to the wavelength of 1.5474 Å by a double-crystal Si (111) monochromator. The datasets were collected in the range of 10° 2θ 130° with a step size of 0.01° (2θ range).

Refinement top

Reflections were indexed using DICVOL (Boultif & Louër, 2004). The cubic symmetry was obviously obtained from sXRD data. Any additional peaks were not detected. The figures of merit were M(20) = 277.6 (19), F(20) = 378 (3). Systematic absences, h = 2n + 1 for h00 observed in the intensity data, suggested the space group P213. As an initial model for the Rietveld refinements, the structural parameters of Na3Al(PO3)N from single crystal data (Conanec et al., 1994) were used. Refinements of structural parameters were carried out using the Fullprof program package (Rodriguez-Carvajal, 2001). The shape of the diffraction peaks was modelled with the Thompson-Cox-Hastings pseudo-Voigt function. A manual background correction was used in the refinements; preferred orientation and absorption effects were not considered. In the final refinement run, the following parameters were refined: zero shift, peak width/shape/asymmetry, scale factor, and crystal structure parameters (lattice parameter, atomic positions, isotropic atomic displacement parameters). The final refinement plot is shown in Fig. 3.

Computing details top

Data collection: local software at 9B HRPD beamline; cell refinement: DICVOL (Boultif & Louër, 2004); data reduction: local software at 9B HRPD beamline; program(s) used to solve structure: coordinates taken from an isotypic compound; program(s) used to refine structure: FULLPROF (Rodriguez-Carvajal, 2001); molecular graphics: DIAMOND (Brandenburg, 1999); software used to prepare material for publication: FULLPROF (Rodriguez-Carvajal, 2001).

Figures top
[Figure 1] Fig. 1. The crystal structure of Na3V(PO3)3N. PO4 tetrahedra are shown with gray shading; Na atoms are orange-colored spheres and V atoms are dark green spheres.
[Figure 2] Fig. 2. The local environments of Na, V and N atoms arranged along [111] in the structure of Na3V(PO3)3N.
[Figure 3] Fig. 3. Rietveld refinement plot of Na3V(PO3)3N based on synchrotron X-ray powder diffraction data. The inset shows an enlarged section of the diffraction pattern.
Trisodium vanadium(III) nitridotriphosphate top
Crystal data top
Na3V(PO3)3NDx = 2.92 Mg m3
Mr = 370.83Synchrotron radiation, λ = 1.547400 Å
Cubic, P213T = 298 K
Hall symbol: P 2ac 2ab 3Particle morphology: powder
a = 9.44783 (5) Ågreen
V = 843.33 (1) Å3flat sheet, 20 × 20 mm
Z = 4
Data collection top
Pohang Light Source 9B HRPD Beamline
diffractometer
Data collection mode: reflection
Radiation source: synchrotronScan method: step
Si 111 monochromator2θmin = 10.060°, 2θmax = 130.500°, 2θstep = 0.010°
Specimen mounting: packed powder pellet
Refinement top
Rp = 0.09112045 data points
Rwp = 0.11935 parameters
Rexp = 0.0750 restraints
RBragg = 0.056(Δ/σ)max = 0.02
χ2 = 2.519
Crystal data top
Na3V(PO3)3NZ = 4
Mr = 370.83Synchrotron radiation, λ = 1.547400 Å
Cubic, P213T = 298 K
a = 9.44783 (5) Åflat sheet, 20 × 20 mm
V = 843.33 (1) Å3
Data collection top
Pohang Light Source 9B HRPD Beamline
diffractometer
Scan method: step
Specimen mounting: packed powder pellet2θmin = 10.060°, 2θmax = 130.500°, 2θstep = 0.010°
Data collection mode: reflection
Refinement top
Rp = 0.091R(F2) = ?
Rwp = 0.119χ2 = 2.519
Rexp = 0.07512045 data points
RBragg = 0.05635 parameters
R(F) = ?0 restraints
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
P10.3326 (3)0.0844 (3)0.2446 (3)0.0143 (4)*
V10.08073 (17)0.08073 (17)0.41927 (17)0.0144 (6)*
Na10.0136 (3)0.0136 (3)0.0136 (3)0.0278 (18)*
Na20.3913 (4)0.3913 (4)0.3913 (4)0.0171 (18)*
Na30.6989 (5)0.1989 (5)0.3011 (5)0.0310 (19)*
O10.2722 (6)0.0265 (6)0.3479 (5)0.0130 (14)*
O20.3727 (5)0.0002 (6)0.1109 (5)0.0073 (15)*
O30.4543 (6)0.1700 (6)0.3106 (6)0.0160 (18)*
N10.1937 (7)0.1937 (7)0.1937 (7)0.012 (3)*
Geometric parameters (Å, º) top
P1—O31.538 (6)Na1—N12.947 (7)
P1—O21.540 (6)Na2—O3viii2.304 (7)
P1—O11.541 (6)Na2—O3v2.304 (7)
P1—N11.738 (7)Na2—O32.304 (7)
V1—O1i1.997 (6)Na2—O2ix2.456 (6)
V1—O1ii1.997 (6)Na2—O2x2.456 (6)
V1—O11.997 (6)Na2—O2xi2.456 (6)
V1—O2iii2.013 (5)Na3—O32.329 (7)
V1—O2iv2.013 (5)Na3—O3x2.329 (7)
V1—O2v2.013 (5)Na3—O3xii2.329 (7)
Na1—O1vi2.561 (6)Na3—O1xiii2.964 (7)
Na1—O1vii2.561 (6)Na3—O1xiv2.964 (7)
Na1—O1i2.561 (6)Na3—O1xi2.964 (7)
Na1—O3vii2.604 (6)N1—P1viii1.738 (7)
Na1—O3i2.604 (6)N1—P1v1.738 (7)
Na1—O3vi2.604 (6)
O3—P1—O2114.9 (6)O1—V1—O2iii90.5 (4)
O3—P1—O1112.2 (6)O1i—V1—O2iv92.2 (4)
O2—P1—O1105.0 (5)O1ii—V1—O2iv90.5 (4)
O3—P1—N1111.4 (6)O1—V1—O2iv176.8 (5)
O2—P1—N1105.4 (6)O2iii—V1—O2iv86.5 (3)
O1—P1—N1107.4 (6)O1i—V1—O2v90.5 (4)
O1i—V1—O1ii90.8 (4)O1ii—V1—O2v176.8 (5)
O1i—V1—O190.8 (4)O1—V1—O2v92.2 (4)
O1ii—V1—O190.8 (4)O2iii—V1—O2v86.5 (3)
O1i—V1—O2iii176.8 (5)O2iv—V1—O2v86.5 (3)
O1ii—V1—O2iii92.2 (4)
Symmetry codes: (i) y, z1/2, x+1/2; (ii) z+1/2, x, y+1/2; (iii) x+1/2, y, z+1/2; (iv) z, x1/2, y+1/2; (v) y, z, x; (vi) x+1/2, y, z1/2; (vii) z1/2, x+1/2, y; (viii) z, x, y; (ix) z+1/2, x+1, y+1/2; (x) y+1/2, z+1/2, x+1; (xi) x+1, y+1/2, z+1/2; (xii) z+1, x1/2, y+1/2; (xiii) y+1, z, x; (xiv) z+1/2, x+1/2, y.
Acknowledgements top

This work was supported by the National Research Foundation of Korea (grant Nos. 2009-0094046 and 2010-0013089). The authors thank Dr Do-Cheon Ahn for his help in performing the sXRD experiment at the Pohang light source.

references
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