α-Ba2P2O7

Zakaria, D.; Erragh, F.; Oudahmane, A.; El-Ghozzi, M.; Avignant, D.

doi:10.1107/S1600536810043539

inorganic compounds

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ISSN: 2056-9890

Volume 66| Part 11| November 2010| Pages i76-i77

https://doi.org/10.1107/S1600536810043539

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α-Ba₂P₂O₇

Driss Zakaria,^a Fatima Erragh,^a Abdelghani Oudahmane,^b Malika El-Ghozzi ^b and Daniel Avignant ^b ^*

^aLaboratoire de Physico-Chimie des Matériaux, Université Chouaib Doukkali, Faculté des Sciences BP 20, 24000 El Jadida, Morocco, and ^bUniversité Blaise Pascal, Laboratoire des Matériaux Inorganiques, UMR CNRS 6002, 24 Avenue des Landais, 63177 Aubière, France
^*Correspondence e-mail: daniel.avignant@univ-bpclermont.fr

(Received 6 October 2010; accepted 25 October 2010; online 31 October 2010)

Single crystals of α-Ba₂P₂O₇, dibarium diphosphate, were obtained by solid-state reaction. The orthorhombic structure is isotypic with α-Sr₂P₂O₇ and is the second polymorph obtained for this composition. The structure is built from two different BaO₉ polyhedra (both with m symmetry), with Ba—O distances in the ranges 2.7585 (10)–3.0850 (6) and 2.5794 (13)–2.9313 (4) Å. These polyhedra are further linked by sharing corners along [010] and either edges or triangular faces perpendicularly to [010] to form the three-dimensional framework. This polyhedral linkage delimits large channels parallel to [010] where the P₂O₇ diphosphate anions are located. These groups (symmetry m) are characterized by a P—O—P angle of 131.52 (9)° and an eclipsed conformation. They are connected to the BaO₉ polyhedra through edges and corners.

Related literature

Besides crystals of the title compound, crystals of the hexagonal polymorph σ-Ba₂P₂O₇ were obtained (ElBelghitti et al. 1995 ). For isotypic structures, see: Hagman et al. (1968 ); Grenier & Masse (1977 ); Barbier & Echard (1998 ). For closely related structures, see: Elmarzouki et al. (1995 ). For polymorphism in Ba₂P₂O₇, see: McCauley & Hummel (1968 ); Mehdi et al. (1977 ); Bian et al. (2004 ); Kokhanovskii (2004 ). For a review of the crystal chemistry of diphosphates, see: Durif (1995 ). For applications of alkaline earth diphosphates, see: Pang et al. (2009 ); Peng et al. (2010 ). For an independent refinement of the α-Ba₂P₂O₇ structure based on data from a hydrothermally grown crystal, see: Heyward et al. (2010 ).

Experimental

Crystal data

Ba₂P₂O₇
M_r = 448.62
Orthorhombic, P n m a
a = 9.2875 (1) Å
b = 5.6139 (1) Å
c = 13.8064 (1) Å
V = 719.85 (2) Å³
Z = 4
Mo Kα radiation
μ = 11.31 mm⁻¹
T = 296 K
0.26 × 0.14 × 0.14 mm

Data collection

Bruker APEXII CCD diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2008 ) T_min = 0.155, T_max = 0.205
18034 measured reflections
4304 independent reflections
3726 reflections with I > 2σ(I)
R_int = 0.028

Refinement

R[F² > 2σ(F²)] = 0.021
wR(F²) = 0.046
S = 1.07
4304 reflections
62 parameters
Δρ_max = 1.59 e Å⁻³
Δρ_min = −1.99 e Å⁻³

Table 1
Selected bond lengths (Å)

Ba1—O3ⁱ	2.7585 (10)
Ba1—O2ⁱⁱ	2.7591 (10)
Ba1—O4ⁱⁱⁱ	2.7978 (13)
Ba1—O2	2.8392 (10)
Ba1—O5	3.0850 (6)
Ba2—O5^iv	2.5794 (13)
Ba2—O3ⁱⁱ	2.7377 (10)
Ba2—O2ⁱⁱⁱ	2.8133 (10)
Ba2—O3^v	2.9094 (10)
Ba2—O4^vi	2.9313 (4)
P1—O5	1.5067 (13)
P1—O2^vii	1.5208 (11)
P1—O2	1.5208 (11)
P1—O1	1.6148 (13)
P2—O4^viii	1.5175 (13)
P2—O3^vii	1.5236 (11)
P2—O3	1.5236 (11)
P2—O1	1.6012 (14)
Symmetry codes: (i) $[x+{\script{1\over 2}}, y, -z+{\script{3\over 2}}]$ ; (ii) $[x+{\script{1\over 2}}, -y+{\script{1\over 2}}, -z+{\script{3\over 2}}]$ ; (iii) -x, -y, -z+1; (iv) $[-x+{\script{1\over 2}}, -y, z-{\script{1\over 2}}]$ ; (v) $[-x-{\script{1\over 2}}, -y, z-{\script{1\over 2}}]$ ; (vi) $[x+{\script{1\over 2}}, y+1, -z+{\script{1\over 2}}]$ ; (vii) $[x, -y-{\script{1\over 2}}, z]$ ; (viii) x, y, z+1.

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

Supporting information

Crystal structure: contains datablocks I, global. DOI: https://doi.org/10.1107/S1600536810043539/wm2413sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536810043539/wm2413Isup2.hkl

checkCIF report

Comment top

Due to their potential applications as optical materials (Pang et al., 2009, Peng et al., 2010), alkaline earth diphosphates exhibit at the present time a growing interest. Since the optical properties are strongly related to the crystal structure, the study of polymorphism in these materials is worth investigating. Besides the hexagonal form σ-Ba₂P₂O₇ described by ElBelghitti et al. (1995), the title compound is the second polymorph for this composition obtained in the form of single-crystals. The orthorhombic title compound α-Ba₂P₂O₇ is isotypic with α-Sr₂P₂O₇ (Hagman et al. 1968; Grenier & Masse, 1977; Barbier & Echard, 1998) and closely related to BaPbP₂O₇ (Elmarzouki et al., 1995). The existence of this polymorph has previously been mentioned by Durif (1995) and several other authors (McCauley & Hummel, 1968; Mehdi et al., 1977; Bian et al., 2004; Kokhanovskii, 2004).

The structure of the α-polymorph is built up from two different BaO₉ polyhedra with Ba—O distances ranging from 2.7585 (10) Å to 3.0850 (6) Å and from 2.5794 (13) Å to 2.9313 (4) Å, respectively. Figure 1 displays details of these coordination polyhedra as well as their linkage by corners, edges or triangular faces to form the three-dimensional framework. This polyhedral linkage delimits large channels parallel to [010] where the P₂O₇ diphosphate groups are located (Fig. 2). These groups (symmetry m) are characterized by a P—O—P angle of 131.52 (9)° and an eclipsed conformation. They are connected to the BaO₉ polyhedra through edges and corners. Each oxygen atom of the P₂O₇ groups, apart from the O1 bridging oxygen, is bonded to three Ba atoms and one phosphorus atom. During the anisotropic refinement of the displacement parameters of the isotypic α-Sr₂P₂O₇ structure (Barbier & Echard, 1998), the authors observed a very strong anisotropy along the b direction for both O5 and O1 atoms located in the (010) mirror plane and interpreted this phenomenon as a possible atomic-scale disorder associated with the local loss of mirror symmetry resulting in a non-centrosymmetric structural arrangement. Such an outstanding feature is still present in our anisotropic structure refinement, although the amplitudes of the atomic displacement parameters are significantly lower, especially for the U₂₂ component of the O5 atom. If the strong anisotropy of the O1 atom is perfectly understandable because of its bridging role, that of the O5 atom strongly bonded to two Ba1 atoms at 3.0850 (6) Å, one Ba2 atom at 2.5794 (13) Å and one P1 atom at 1.5067 (13) Å is more surprising. However, due to the relative homogeneity of the values of the isotropic displacement parameters of all oxygen atoms, it does not seem necessary to envisage any atomic-scale disorder for the O5 atom in the present case.

Simultaneous with our refinement, an independent study of the α-Ba₂P₂O₇ structure from a hydrothermally grown crystal was reported by Heyward et al. (2010). The results of both refinements in terms of geometric parameters are the same within the threefold standard deviation.

Related literature top

Besides crystals of the title compound, crystals of the hexagonal polymorph σ-Ba₂P₂O₇ were obtained (ElBelghitti et al. 1995). For isotypic structures, see: Hagman et al. (1968); Grenier & Masse (1977); Barbier & Echard (1998). For closely related structures, see: Elmarzouki et al. (1995). For polymorphism in Ba₂P₂O₇, see: McCauley & Hummel (1968); Mehdi et al. (1977); Bian et al. (2004); Kokhanovskii (2004). For a review of the crystal chemistry of diphosphates, see: Durif (1995). For applications of alkaline earth diphosphates, see: Pang et al. (2009); Peng et al. (2010). For an independent refinement of the α-Ba₂P₂O₇ structure based on data from a hydrothermally grown crystal, see: Heyward et al. (2010).

Experimental top

Single crystals of the title compound have been obtained during the study of the phase relationships in the ternary system Na₂O—BaO—P₂O₅. They were synthesized in the solid state by reacting Na₂CO₃, BaCO₃ and (NH₄)₂HPO₄ in a platinum crucible. A mixture of these reagents taken in the molar ratio 1: 1: 2 was carefully ground in an agate mortar and successively heated at 373 K, 573 K and 773 K for 24 h at each temperature. After a new grinding, the reacting mixture was submitted to a final heat treatment at 973 K for 2 days followed by a slow cooling to room temperature at the rate of 5 K h^-1. After an abundant washing of the batch with hot water, single crystals of the title compound could have been extracted.

Structure description top

Besides crystals of the title compound, crystals of the hexagonal polymorph σ-Ba₂P₂O₇ were obtained (ElBelghitti et al. 1995). For isotypic structures, see: Hagman et al. (1968); Grenier & Masse (1977); Barbier & Echard (1998). For closely related structures, see: Elmarzouki et al. (1995). For polymorphism in Ba₂P₂O₇, see: McCauley & Hummel (1968); Mehdi et al. (1977); Bian et al. (2004); Kokhanovskii (2004). For a review of the crystal chemistry of diphosphates, see: Durif (1995). For applications of alkaline earth diphosphates, see: Pang et al. (2009); Peng et al. (2010). For an independent refinement of the α-Ba₂P₂O₇ structure based on data from a hydrothermally grown crystal, see: Heyward et al. (2010).

Computing details top

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

Figures top

Fig. 1. View of the BaO₉ polyhedra linkage in α-Ba₂P₂O₇. Displacement ellipsoids are drawn at the 50% probability level. Symmetry codes: (i) x + 1/2, y, -z + 3/2; (ii) x + 1/2, -y + 1/2, -z + 3/2; (iii) -x, -y, -z + 1; (iv) x, -y + 1/2, z; (v) x, y + 1, z; (vii) -x, y + 1/2, -z + 1; (viii) -x - 1/2, -y, z - 1/2; (ix) -x - 1/2, y + 1/2, z - 1/2; (x) x + 1/2, y + 1, -z + 1/2; (xi) x + 1/2, y, -z + 1/2; (xii) x + 1/2, y + 1, -z + 3/2; (xiii) x, -y - 1/2, z; (xiv) x, y, z + 1; (xv) -x - 1/2, -y, z + 1/2; (xvi) x - 1/2, y, -z + 3/2; (xviii) x, y, z - 1; -z + 1/2; (xx) x - 1/2, y, -z + 1/2; (xxi) -x + 1/2, -y, z + 1/2; (xxii) x, y - 1, z;

Fig. 2. Projection of the α-Ba₂P₂O₇ structure along [010] showing the connections between the P₂O₇ diphosphate groups and the three-dimensional framework of the BaO₉ polyhedra.

dibarium diphosphate top

Crystal data top

Ba₂P₂O₇	F(000) = 792
M_r = 448.62	D_x = 4.139 Mg m⁻³
Orthorhombic, Pnma	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ac 2n	Cell parameters from 7790 reflections
a = 9.2875 (1) Å	θ = 3.7–52.2°
b = 5.6139 (1) Å	µ = 11.31 mm⁻¹
c = 13.8064 (1) Å	T = 296 K
V = 719.85 (2) Å³	Hexagonal prism, colourless
Z = 4	0.26 × 0.14 × 0.14 mm

Data collection top

Bruker APEXII CCD diffractometer	4304 independent reflections
Radiation source: fine-focus sealed tube	3726 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.028
Detector resolution: 8.3333 pixels mm^-1	θ_max = 52.4°, θ_min = 4.5°
ω and φ scans	h = −17→20
Absorption correction: multi-scan (SADABS; Bruker, 2008)	k = −12→10
T_min = 0.155, T_max = 0.205	l = −30→28
18034 measured reflections

Refinement top

Refinement on F²	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F² > 2σ(F²)] = 0.021	w = 1/[σ²(F_o²) + (0.0176P)² + 0.4317P] where P = (F_o² + 2F_c²)/3
wR(F²) = 0.046	(Δ/σ)_max = 0.004
S = 1.07	Δρ_max = 1.59 e Å⁻³
4304 reflections	Δρ_min = −1.99 e Å⁻³
62 parameters	Extinction correction: SHELXL97 (Sheldrick, 2008), Fc^*=kFc[1+0.001xFc²λ³/sin(2θ)]^-1/4
0 restraints	Extinction coefficient: 0.0075 (2)

Crystal data top

Ba₂P₂O₇	V = 719.85 (2) Å³
M_r = 448.62	Z = 4
Orthorhombic, Pnma	Mo Kα radiation
a = 9.2875 (1) Å	µ = 11.31 mm⁻¹
b = 5.6139 (1) Å	T = 296 K
c = 13.8064 (1) Å	0.26 × 0.14 × 0.14 mm

Data collection top

Bruker APEXII CCD diffractometer	4304 independent reflections
Absorption correction: multi-scan (SADABS; Bruker, 2008)	3726 reflections with I > 2σ(I)
T_min = 0.155, T_max = 0.205	R_int = 0.028
18034 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.021	62 parameters
wR(F²) = 0.046	0 restraints
S = 1.07	Δρ_max = 1.59 e Å⁻³
4304 reflections	Δρ_min = −1.99 e Å⁻³

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

	x	y	z	U_iso*/U_eq
Ba1	0.159652 (9)	0.2500	0.744870 (6)	0.00801 (2)
Ba2	0.138138 (9)	0.2500	0.417071 (6)	0.00841 (2)
P1	−0.04603 (4)	−0.2500	0.81569 (3)	0.00724 (6)
P2	−0.28072 (4)	−0.2500	0.95778 (3)	0.00722 (6)
O1	−0.11642 (14)	−0.2500	0.92264 (9)	0.0129 (2)
O2	−0.09496 (10)	−0.0264 (2)	0.76295 (7)	0.01169 (13)
O3	−0.35537 (10)	−0.0271 (2)	0.91982 (6)	0.01215 (14)
O4	−0.27382 (15)	−0.2500	0.06760 (9)	0.0130 (2)
O5	0.11429 (14)	−0.2500	0.83242 (11)	0.0160 (3)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Ba1	0.00795 (3)	0.00736 (4)	0.00873 (3)	0.000	−0.00047 (2)	0.000
Ba2	0.00856 (3)	0.00891 (4)	0.00776 (3)	0.000	0.00084 (2)	0.000
P1	0.00544 (11)	0.00757 (16)	0.00873 (13)	0.000	0.00010 (9)	0.000
P2	0.00839 (12)	0.00706 (16)	0.00622 (12)	0.000	0.00066 (9)	0.000
O1	0.0088 (4)	0.0198 (7)	0.0100 (4)	0.000	0.0012 (3)	0.000
O2	0.0126 (3)	0.0091 (4)	0.0133 (3)	0.0008 (3)	0.0005 (2)	0.0022 (3)
O3	0.0145 (3)	0.0101 (4)	0.0119 (3)	0.0029 (3)	0.0000 (2)	0.0022 (3)
O4	0.0161 (5)	0.0160 (6)	0.0069 (4)	0.000	0.0003 (3)	0.000
O5	0.0061 (3)	0.0243 (8)	0.0176 (5)	0.000	−0.0008 (3)	0.000

Geometric parameters (Å, º) top

Ba1—O3ⁱ	2.7585 (10)	P1—O2^xiii	1.5208 (11)
Ba1—O3ⁱⁱ	2.7585 (10)	P1—O2	1.5208 (11)
Ba1—O2ⁱⁱ	2.7591 (10)	P1—O1	1.6148 (13)
Ba1—O2ⁱ	2.7591 (10)	P1—Ba2ⁱⁱⁱ	3.3255 (4)
Ba1—O4ⁱⁱⁱ	2.7978 (13)	P2—O4^xiv	1.5175 (13)
Ba1—O2	2.8392 (10)	P2—O3^xiii	1.5236 (11)
Ba1—O2^iv	2.8392 (10)	P2—O3	1.5236 (11)
Ba1—O5^v	3.0850 (6)	P2—O1	1.6012 (14)
Ba1—O5	3.0850 (6)	P2—Ba2^xv	3.3668 (4)
Ba2—O5^vi	2.5794 (13)	P2—Ba2^xvi	3.3812 (2)
Ba2—O3ⁱⁱ	2.7377 (10)	P2—Ba2^xvii	3.3812 (2)
Ba2—O3ⁱ	2.7377 (10)	O2—Ba1^xvi	2.7591 (10)
Ba2—O2ⁱⁱⁱ	2.8133 (10)	O2—Ba2ⁱⁱⁱ	2.8133 (10)
Ba2—O2^vii	2.8133 (10)	O3—Ba2^xvi	2.7377 (10)
Ba2—O3^viii	2.9094 (10)	O3—Ba1^xvi	2.7585 (10)
Ba2—O3^ix	2.9094 (10)	O3—Ba2^xv	2.9094 (10)
Ba2—O4^x	2.9313 (4)	O4—P2^xviii	1.5175 (13)
Ba2—O4^xi	2.9313 (4)	O4—Ba1ⁱⁱⁱ	2.7978 (13)
Ba2—P1ⁱⁱⁱ	3.3255 (4)	O4—Ba2^xix	2.9313 (4)
Ba2—P2^viii	3.3668 (4)	O4—Ba2^xx	2.9313 (4)
Ba2—P2^xii	3.3812 (2)	O5—Ba2^xxi	2.5794 (13)
P1—O5	1.5067 (13)	O5—Ba1^xxii	3.0850 (6)

O3ⁱ—Ba1—O3ⁱⁱ	68.66 (5)	O3ⁱⁱ—Ba2—O3^ix	76.39 (3)
O3ⁱ—Ba1—O2ⁱⁱ	109.06 (3)	O3ⁱ—Ba2—O3^ix	104.688 (19)
O3ⁱⁱ—Ba1—O2ⁱⁱ	72.09 (3)	O2ⁱⁱⁱ—Ba2—O3^ix	94.29 (3)
O3ⁱ—Ba1—O2ⁱ	72.09 (3)	O2^vii—Ba2—O3^ix	71.99 (3)
O3ⁱⁱ—Ba1—O2ⁱ	109.06 (3)	O3^viii—Ba2—O3^ix	50.95 (4)
O2ⁱⁱ—Ba1—O2ⁱ	68.43 (4)	O5^vi—Ba2—O4^x	77.53 (3)
O3ⁱ—Ba1—O4ⁱⁱⁱ	141.44 (2)	O3ⁱⁱ—Ba2—O4^x	52.44 (3)
O3ⁱⁱ—Ba1—O4ⁱⁱⁱ	141.44 (3)	O3ⁱ—Ba2—O4^x	118.59 (3)
O2ⁱⁱ—Ba1—O4ⁱⁱⁱ	73.93 (3)	O2ⁱⁱⁱ—Ba2—O4^x	122.07 (3)
O2ⁱ—Ba1—O4ⁱⁱⁱ	73.93 (3)	O2^vii—Ba2—O4^x	71.11 (3)
O3ⁱ—Ba1—O2	73.87 (3)	O3^viii—Ba2—O4^x	131.51 (3)
O3ⁱⁱ—Ba1—O2	109.79 (3)	O3^ix—Ba2—O4^x	80.73 (3)
O2ⁱⁱ—Ba1—O2	177.035 (6)	O5^vi—Ba2—O4^xi	77.53 (3)
O2ⁱ—Ba1—O2	112.59 (4)	O3ⁱⁱ—Ba2—O4^xi	118.59 (3)
O4ⁱⁱⁱ—Ba1—O2	103.55 (3)	O3ⁱ—Ba2—O4^xi	52.44 (3)
O3ⁱ—Ba1—O2^iv	109.79 (3)	O2ⁱⁱⁱ—Ba2—O4^xi	71.11 (3)
O3ⁱⁱ—Ba1—O2^iv	73.87 (3)	O2^vii—Ba2—O4^xi	122.07 (3)
O2ⁱⁱ—Ba1—O2^iv	112.59 (4)	O3^viii—Ba2—O4^xi	80.73 (3)
O2ⁱ—Ba1—O2^iv	177.035 (6)	O3^ix—Ba2—O4^xi	131.51 (3)
O4ⁱⁱⁱ—Ba1—O2^iv	103.55 (3)	O4^x—Ba2—O4^xi	146.51 (5)
O2—Ba1—O2^iv	66.25 (4)	O5—P1—O2^xiii	111.63 (5)
O3ⁱ—Ba1—O5^v	146.01 (3)	O5—P1—O2	111.63 (5)
O3ⁱⁱ—Ba1—O5^v	78.63 (3)	O2^xiii—P1—O2	111.29 (8)
O2ⁱⁱ—Ba1—O5^v	67.45 (3)	O5—P1—O1	105.06 (8)
O2ⁱ—Ba1—O5^v	129.77 (3)	O2^xiii—P1—O1	108.47 (5)
O4ⁱⁱⁱ—Ba1—O5^v	71.89 (3)	O2—P1—O1	108.47 (5)
O2—Ba1—O5^v	110.43 (3)	P2—O1—P1	131.52 (9)
O2^iv—Ba1—O5^v	49.81 (3)	P1—O2—Ba1^xvi	136.86 (5)
O3ⁱ—Ba1—O5	78.63 (3)	P1—O2—Ba2ⁱⁱⁱ	95.57 (5)
O3ⁱⁱ—Ba1—O5	146.01 (3)	Ba1^xvi—O2—Ba2ⁱⁱⁱ	95.66 (3)
O2ⁱⁱ—Ba1—O5	129.77 (3)	P1—O2—Ba1	104.14 (5)
O2ⁱ—Ba1—O5	67.45 (3)	Ba1^xvi—O2—Ba1	112.16 (4)
O4ⁱⁱⁱ—Ba1—O5	71.89 (3)	Ba2ⁱⁱⁱ—O2—Ba1	106.55 (3)
O2—Ba1—O5	49.81 (3)	P2—O3—Ba2^xvi	101.17 (4)
O2^iv—Ba1—O5	110.43 (3)	P2—O3—Ba1^xvi	136.36 (5)
O5^v—Ba1—O5	130.97 (5)	Ba2^xvi—O3—Ba1^xvi	111.02 (4)
O5^vi—Ba2—O3ⁱⁱ	110.68 (3)	P2—O3—Ba2^xv	93.55 (5)
O5^vi—Ba2—O3ⁱ	110.68 (3)	Ba2^xvi—O3—Ba2^xv	103.61 (3)
O3ⁱⁱ—Ba2—O3ⁱ	69.25 (4)	Ba1^xvi—O3—Ba2^xv	106.11 (3)
O5^vi—Ba2—O2ⁱⁱⁱ	74.14 (3)	P2^xviii—O4—Ba1ⁱⁱⁱ	160.15 (8)
O3ⁱⁱ—Ba2—O2ⁱⁱⁱ	169.56 (3)	P2^xviii—O4—Ba2^xix	93.46 (3)
O3ⁱ—Ba2—O2ⁱⁱⁱ	118.44 (3)	Ba1ⁱⁱⁱ—O4—Ba2^xix	92.23 (3)
O5^vi—Ba2—O2^vii	74.14 (3)	P2^xviii—O4—Ba2^xx	93.46 (3)
O3ⁱⁱ—Ba2—O2^vii	118.44 (3)	Ba1ⁱⁱⁱ—O4—Ba2^xx	92.23 (3)
O3ⁱ—Ba2—O2^vii	169.56 (3)	Ba2^xix—O4—Ba2^xx	146.51 (5)
O2ⁱⁱⁱ—Ba2—O2^vii	53.01 (4)	P1—O5—Ba2^xxi	161.87 (9)
O5^vi—Ba2—O3^viii	144.15 (3)	P1—O5—Ba1^xxii	94.30 (3)
O3ⁱⁱ—Ba2—O3^viii	104.688 (19)	Ba2^xxi—O5—Ba1^xxii	93.20 (3)
O3ⁱ—Ba2—O3^viii	76.39 (3)	P1—O5—Ba1	94.30 (3)
O2ⁱⁱⁱ—Ba2—O3^viii	71.99 (3)	Ba2^xxi—O5—Ba1	93.20 (3)
O2^vii—Ba2—O3^viii	94.29 (3)	Ba1^xxii—O5—Ba1	130.97 (5)
O5^vi—Ba2—O3^ix	144.15 (3)

Symmetry codes: (i) x+1/2, y, −z+3/2; (ii) x+1/2, −y+1/2, −z+3/2; (iii) −x, −y, −z+1; (iv) x, −y+1/2, z; (v) x, y+1, z; (vi) −x+1/2, −y, z−1/2; (vii) −x, y+1/2, −z+1; (viii) −x−1/2, −y, z−1/2; (ix) −x−1/2, y+1/2, z−1/2; (x) x+1/2, y+1, −z+1/2; (xi) x+1/2, y, −z+1/2; (xii) x+1/2, y+1, −z+3/2; (xiii) x, −y−1/2, z; (xiv) x, y, z+1; (xv) −x−1/2, −y, z+1/2; (xvi) x−1/2, y, −z+3/2; (xvii) x−1/2, y−1, −z+3/2; (xviii) x, y, z−1; (xix) x−1/2, y−1, −z+1/2; (xx) x−1/2, y, −z+1/2; (xxi) −x+1/2, −y, z+1/2; (xxii) x, y−1, z.

Experimental details

Crystal data
Chemical formula	Ba₂P₂O₇
M_r	448.62
Crystal system, space group	Orthorhombic, Pnma
Temperature (K)	296
a, b, c (Å)	9.2875 (1), 5.6139 (1), 13.8064 (1)
V (Å³)	719.85 (2)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	11.31
Crystal size (mm)	0.26 × 0.14 × 0.14

Data collection
Diffractometer	Bruker APEXII CCD
Absorption correction	Multi-scan (SADABS; Bruker, 2008)
T_min, T_max	0.155, 0.205
No. of measured, independent and observed [I > 2σ(I)] reflections	18034, 4304, 3726
R_int	0.028
(sin θ/λ)_max (Å⁻¹)	1.115

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.021, 0.046, 1.07
No. of reflections	4304
No. of parameters	62
Δρ_max, Δρ_min (e Å⁻³)	1.59, −1.99

Computer programs: APEX2 (Bruker, 2008), SAINT (Bruker, 2008), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), DIAMOND (Brandenburg, 1999) and ORTEP-3 for Windows (Farrugia, 1997), SHELXTL (Sheldrick, 2008).

Selected bond lengths (Å) top

Ba1—O3ⁱ	2.7585 (10)	Ba2—O4^vi	2.9313 (4)
Ba1—O2ⁱⁱ	2.7591 (10)	P1—O5	1.5067 (13)
Ba1—O4ⁱⁱⁱ	2.7978 (13)	P1—O2^vii	1.5208 (11)
Ba1—O2	2.8392 (10)	P1—O2	1.5208 (11)
Ba1—O5	3.0850 (6)	P1—O1	1.6148 (13)
Ba2—O5^iv	2.5794 (13)	P2—O4^viii	1.5175 (13)
Ba2—O3ⁱⁱ	2.7377 (10)	P2—O3^vii	1.5236 (11)
Ba2—O2ⁱⁱⁱ	2.8133 (10)	P2—O3	1.5236 (11)
Ba2—O3^v	2.9094 (10)	P2—O1	1.6012 (14)

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

Acknowledgements

This work was supported by the French–Moroccan integrated action (grant No. MA/05/119 F).

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