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The previously unknown crystal structure of strontium mag­nesium phosphate, Sr2+xMg3-xP4O15 (x ~ 0.36), determined and refined from laboratory powder X-ray diffraction data, represents a new structure type. The title compound was synthesized by high-temperature solid-state reaction and it crystallizes in the ortho­rhom­bic space group Cmcm. It was earlier thought to be stoichiometric Sr2Mg3P4O15, but our structural study indicates the nonstoichiometric composition. The asymmetric unit contains one Sr (site symmetry ..m on special position 8g), one M (= Mg 64%/Sr 36%; site symmetry 2/m.. on special position 4b), one Mg (site symmetry 2.. on special position 8e), two P (site symmetry m.. on special position 8f and site symmetry ..m on special position 8g), and six O sites [two on general positions 16h, two on 8g, one on 8f and one on special position 4c (site symmetry m2m)]. The nonstoichiometry is due to the mixing of magnesium and strontium ions on the M site. The structure consists of three-dimensional networks of MgO4 and PO4 tetra­hedra, and MO6 octa­hedra with the other strontium ions occupying the larger cavities surrounded by ten O atoms. All the polyhedra are connected by corner-sharing except the edge-sharing MO6 octa­hedra forming one-dimensional arrangements along [001].

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270110047967/sq3270sup1.cif
Contains datablocks global, phase_1, phase_2, phase_3

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270110047967/sq3270phase_1sup2.hkl
Contains datablock phase_1

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270110047967/sq3270phase_2sup3.hkl
Contains datablock phase_2

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270110047967/sq3270phase_3sup4.hkl
Contains datablock phase_3

Comment top

Sr2Mg3P4O15:Eu2+ was recently reported to show potential for application as a blue phosphor for a white LED under excitation of near-UV light (Ngee et al., 2009; Guo et al., 2010). The existence of a single phase in the system SrO–MgO–P2O5 was first confirmed over 40 years ago (Hoffman, 1968), but only un-indexed X-ray diffraction data were reported and its crystal structure has remained unknown. In the present study, during the course of crystal structure determination we have discovered that the compound previously known as Sr2Mg3P4O15 is in fact nonstoichiometric Sr2+xMg3-xP4O15 (x~0.36). Here we present its crystal structure, as determined and refined from laboratory powder X-ray diffraction data (Fig. 1).

Sr2+xMg3-xP4O15 crystallizes in a new structure type in terms of atomic ratios (6:1:2:15 for tetrahedral:octahedral:ten-coordinated metal:oxygen) and its polyhedral network is, to our knowledge, unique. The structure consists of (Mg2)O4, (P1)O4, and (P2)O4 tetrahedra, and MO6 octahedra, where M ( Mg1/Sr2) represents disordered magnesium (Mg1, 64%) and strontium (Sr2, 36%) ions (Fig. 2). The other strontium (Sr1) ions occupy the larger cavities surrounded by O atoms with tenfold coordination (Fig. 3). Each (Mg2)O4 tetrahedron is engaged in corner-sharing with two (P1)O4 and two (P2)O4 tetrahedra. (P1)O4 corner-shares with another (P1)O4 (to form a P2O7 group), two (Mg2)O4 and one MO6 polyhedra. (P2)O4 is connected to only two polyhedra: (Mg2)O4 and MO6. Each O6 atom in the other two corners of the P2 tetrahedron is bonded to two Sr1 ions, one in common to both O atoms. The MO6 octahedra form one-dimensional arrangements along [001], sharing edges. Each MO6 is also engaged in corner-sharing with two opposite-sided (P1)O4 tetrahedra along [010] and four (P2)O4 tetrahedra parallel to the (010) plane. The average M—O distance of 2.265 Å is very close to the expected value from the sum of M and O ionic radii (2.27Å) weighted by 64% Mg and 36% Sr (Shannon, 1976).

The empirical expression for bond valence, which has been widely adopted to estimate valences in inorganic solids (Brown, 2002), was used to check the Sr2+xMg3-xP4O15 (x~0.36) crystal structure. The bond-valence sums (Brown & Altermatt, 1985; Brese & O'Keeffe, 1991) calculated with the program VaList (Wills, 2010) for Sr1 (2.04 v.u.), (Mg1/Sr2) (2.30), Mg2 (2.11), P1 (5.06), P2 (4.86), O1 (2.09), O2 (2.12), O3 (2.00), O4 (2.12), O5 (2.20) and O6 (1.85) match the expected charges of the ions reasonably well. The higher valence sum for (Mg1/Sr2) resulted from the shorter Sr2—O bond distances (2.265 Å). All the other interatomic distances (Table 1) are within the expected ranges.

The nonstoichiometry model with more strontium and fewer magnesium ions also conformed to the synthesis results that magnesium phosphates were the impurity phases. Several trials to prepare a single phase Sr2+xMg3-xP4O15 (x~0.36) with the nonstoichiometric nominal composition under the same synthesis conditions were unsuccessful: the magnesium phosphate impurities disappeared but instead SrMgP2O7 (Tahiri et al., 2002) appeared as an impurity phase in the X-ray diffraction pattern. The relative atomic stoichiometries of Sr2.36Mg2.64P4O15 and SrMgP2O7 are quite similar and they seemed to compete with each other kinetically and/or thermodynamically in our synthetic condition. More careful work should be undertaken to determine a reproducible synthetic condition for the single phase, which is beyond the purpose of the present study.

The crystal structure of SrMgP2O7 is rather simple compared to Sr2.36Mg2.64P4O15. It consists of PO4 tetrahedra, MgO5 square-pyramids and eight-coordinated strontium ions occupying the larger cavities surrounded by O atoms. Each PO4 corner-shares with another PO4 [to form a P2O7 group, similar to (P1)O4 in Sr2.36Mg2.64P4O15] and three MgO5 polyhedra. All five corners of MgO5 are connected to PO4 tetrahedra. There is no MgO4 tetrahedron or octahedron in this structure, unlike Sr2.36Mg2.64P4O15.

Related literature top

For related literature, see: Betteridge et al. (2003); Boultif & Louër (1991); Brese & O'Keeffe (1991); Brown (2002); Brown & Altermatt (1985); Calvo (1967); Guo et al. (2010); Hoffman (1968); Larson & Von Dreele (2000); Lee & Hong (2008); Ngee et al. (2009); Nord & Kierkegaard (1968); Rohlíček & Hušák (2007); Shannon (1976); Sheldrick (2008); Shirley (2002); Tahiri et al. (2002); Wills (2010).

Experimental top

Sr2+xMg3-xP4O15 (x~0.36) was synthesized by a solid-state reaction from a mixture of high-purity SrCO3 (99.994%, Alfa Aesar), MgO (99.0%, Yakuri Pure Chemicals) and (NH4)2HPO4 (99.0%, Junsei Chemical) with a nominal composition of (Sr: Mg: P = 2: 3: 4). The mixture was thoroughly ground in an agate mortar, dried, pressed into a pellet, heated in air at 1303 K for 4 h, and again at 1323 K for 4 h with intermediate grinding and pressing. The yield was about 90% by weight. The nonstoichiometric composition of the major phase, Sr2+xMg3-xP4O15 (x~0.36), was determined later by the structural refinement, and the minor impurity phases were determined to be Mg2P2O7 (Calvo, 1967) and Mg3P2O8 (Nord & Kierkegaard, 1968).

Refinement top

The powder X-ray diffraction (XRD) data were collected at room temperature on a Bragg–Brentano diffractometer (Bruker AXS Advance D8) with a Cu X-ray tube, a focusing primary Ge (111) monochromator (λ = 1.5406 Å) and a position-sensitive Väntec detector with a 6° slit. Data acquisition covered the angular range 8° 2θ 140° at a step width of 0.016682° and a total measurement time of 40 h. The structure determination from the powder XRD data was performed using a combination of the powder profile refinement program GSAS (Larson & Von Dreele, 2000) and the single-crystal structure refinement program CRYSTALS (Betteridge et al., 2003). For a three-dimensional view of the Fourier density maps, MCE was used (Rohlíček & Hušák, 2007). The XRD pattern was indexed using the program DICVOL91 (Boultif & Louër, 1991) run in CRYSFIRE (Shirley, 2002) via the positions of 20 diffraction peaks after excluding the impurity peaks, resulting in an orthorhombic unit cell. The systematic absences suggested three possible space groups: Cmc21, C2cm and Cmcm. All of them would have resulted in basically the same structure, thus the space group Cmcm with the highest symmetry was chosen for the final refinement. LeBail fitting was carried out for the previously unknown phase of Sr2+xMg3-xP4O15, while Rietveld fitting was carried out for the two known impurity phases.

The structure determination was performed in the same way as in our previous work (Lee & Hong, 2008) where the details were described. At the beginning, a structural model with only a dummy atom at an arbitrary position in the unit cell was used. Structure factors were extracted from the powder data, then direct methods were used for the initial solution of the structure using SHELXS (Sheldrick, 2008) run in CRYSTALS, which yielded several metal positions. However, not all the atoms could be identified at once. The partial model at this stage replaced the initial dummy-atom model, and was used for a LeBail fit in GSAS. Then, improved structure factors were extracted, which were used for the improved data in the refinement in CRYSTALS. These processes were iterated until a complete and satisfactory structural model was obtained. Finally, Rietveld refinement was employed to complete the structure determination. Up to this step, a stoichiometric composition of Sr2Mg3P4O15 was assumed for the unknown phase, and indeed the crystallographic sites ratio seemed to conform to the stoichiometry. However, the thermal parameter of the Mg1 site went to a very small value, and Mg1—O distances (circa 2.3 Å) were longer than the expected (2.10 Å), but much shorter than the 2.56 Å expected for d(Sr—O) from ionic radii (Shannon, 1976). Therefore, it was assumed that some magnesium is substituted by strontium in the Mg1 site, and Sr2 and Mg1 occupancies were refined with a constraint that the thermal parameters for M (Mg1/Sr2) and Mg2 sites were the same, resulting in a dramatic improvement in refinement (wRp factors from 16.8 to 6.3%) with reasonable thermal parameters. Lowering the symmetry to Cmc21 or C2cm did not separate the problematic Mg1 site, and thus should not make any difference to this outcome. For the impurity phases, only the cell parameters and scale factors were refined while the other variables were fixed in the final refinement. The overall fit (wRp = 6.3%) is shown in Fig. 1.

Computing details top

For all compounds, data collection: COMMANDER (Bruker, 2003); cell refinement: GSAS (Larson & Von Dreele, 2000); data reduction: EVA (Bruker, 2003); program(s) used to solve structure: SHELXS (Sheldrick, 2008) and CRYSTALS (Betteridge et al., 2003); program(s) used to refine structure: GSAS (Larson & Von Dreele, 2000); molecular graphics: ATOMS (Dowty, 2000); software used to prepare material for publication: GSAS (Larson & Von Dreele, 2000).

Figures top
[Figure 1] Fig. 1. X-ray Rietveld refinement profiles for Sr2+xMg3-xP4O15 (x~0.36) including the minor impurity phases, recorded at room temperature. The crossed line marks experimental points and the solid line is the calculated profile. The bottom trace shows the difference curve, and the ticks denote expected peak positions for Sr2+xMg3-xP4O15 (x~0.36), Mg2P2O7 and Mg3P2O8, respectively, in order from the bottom.
[Figure 2] Fig. 2. Views of the structure along (001) (a) and (010) (b) with the unit cell outlined.
[Figure 3] Fig. 3. The local environment of strontium (Sr1). [Symmetry codes: (i) x, 1 - y, -z; (ii) x, 1 - y, 1/2 + z; (iii) x, y, 1/2 - z; (iv) 1/2 - x, 1/2 + y, z; (v) 1/2 - x, y – 1/2, z; (vi) 1/2 - x, y – 1/2, 1/2 – z]
(phase_1) distrontium dimagnesium pentadecaoxidotetraphosphate top
Crystal data top
Sr2.36Mg2.64P4O15Z = 4
Mr = 634.65F(000) = 1204.4
Orthorhombic, CmcmDx = 3.490 Mg m3
Hall symbol: -C 2c 2Cu Kα1 radiation, λ = 1.5406 Å
a = 14.27366 (9) ÅT = 296 K
b = 11.75678 (7) Åwhite
c = 7.19753 (4) Åflat sheet, 20 × 20 mm
V = 1207.83 (1) Å3Specimen preparation: Prepared at 296 K
Data collection top
Bruker D8 Advance
diffractometer
Data collection mode: reflection
Radiation source: sealed X-ray tube, Bruker Cu Ceramic X-ray tubeScan method: step
Ge 111 monochromator2θmin = 8.0°, 2θmax = 140.422°, 2θstep = 0.017°
Specimen mounting: packed powder pellet
Refinement top
Least-squares matrix: full7939 data points
Rp = 0.048Profile function: CW Profile function number 4 with 18 terms Pseudovoigt profile coefficients as parameterized in Thompson et al. [Thompson, P., Cox, D. E. & Hastings, J. B. (1987). J. Appl. Cryst. 20, 79–83]. Asymmetry correction of Finger et al. [Finger, L. W., Cox, D. E. & Jephcoat, A. P. (1994). J. Appl. Cryst. 27, 892–900]. Microstrain broadening by Stephens [Stephens, P. W. (1999). J. Appl. Cryst. 32, 281–289]. #1(GU) = 101.674 #2(GV) = -32.707 #3(GW) = 2.792 #4(GP) = 11.704 #5(LX) = 5.714 #6(ptec) = 0.00 #7(trns) = 0.00 #8(shft) = 3.1799 #9(sfec) = 0.00 #10(S/L) = 0.0087 #11(H/L) = 0.0005 #12(eta) = 0.7500 #13(S400 ) = 0.0E+00 #14(S040 ) = 0.0E+00 #15(S004 ) = 0.0E+00 #16(S220 ) = 0.0E+00 #17(S202 ) = 0.0E+00 #18(S022 ) = 0.0E+00 Peak tails are ignored where the intensity is below 0.0020 times the peak Aniso. broadening axis 0.0 0.0 1.0
Rwp = 0.06381 parameters
Rexp = 0.0250 restraints
RBragg = 0.047Weighting scheme based on measured s.u.'s
R(F) = 0.028(Δ/σ)max = 0.02
R(F2) = 0.04372Background function: GSAS Background function number 1 with 36 terms. Shifted Chebyshev function of 1st kind 1: 667.815 2: -121.026 3: 250.928 4: -108.029 5: 130.095 6: -120.393 7: 81.5238 8: -66.4354 9: 31.4946 10: -19.2674 11: 16.0150 12: -21.1906 13: 24.6787 14: -7.73173 15: 5.82669 16: 7.16351 17: 9.66948 18: 8.02466 19: 5.65618 20: 4.74674 21: -11.8793 22: -0.873263 23: -2.40368 24: -9.55052 25: -6.36605 26: 6.28370 27: -8.07052 28: 6.33955 29: -12.6008 30: 3.68005 31: 5.95000 32: 7.62516 33: 1.58465 34: 5.63269 35: -2.90398 36: 14.7130
χ2 = 6.250
Crystal data top
Sr2.36Mg2.64P4O15V = 1207.83 (1) Å3
Mr = 634.65Z = 4
Orthorhombic, CmcmCu Kα1 radiation, λ = 1.5406 Å
a = 14.27366 (9) ÅT = 296 K
b = 11.75678 (7) Åflat sheet, 20 × 20 mm
c = 7.19753 (4) Å
Data collection top
Bruker D8 Advance
diffractometer
Scan method: step
Specimen mounting: packed powder pellet2θmin = 8.0°, 2θmax = 140.422°, 2θstep = 0.017°
Data collection mode: reflection
Refinement top
Rp = 0.048R(F2) = 0.04372
Rwp = 0.063χ2 = 6.250
Rexp = 0.0257939 data points
RBragg = 0.04781 parameters
R(F) = 0.0280 restraints
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/UeqOcc. (<1)
Sr10.16729 (5)0.29123 (6)0.250.0157 (2)*
Sr20.00.50.00.0185 (4)*0.3571 (23)
Mg10.00.50.00.0185 (4)*0.6429 (23)
Mg20.16691 (18)0.00.00.0185 (4)*
P10.00.80342 (16)0.0344 (3)0.0148 (4)*
P20.19114 (12)0.57060 (18)0.250.0148 (4)*
O10.00.6879 (4)0.0498 (5)0.0250 (5)*
O20.0979 (3)0.5046 (4)0.250.0250 (5)*
O30.08811 (19)0.1331 (2)0.0171 (4)0.0250 (5)*
O40.2279 (3)0.0215 (4)0.250.0250 (5)*
O50.00.7839 (6)0.250.0250 (5)*
O60.2059 (2)0.6400 (3)0.0769 (4)0.0250 (5)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
???????
Geometric parameters (Å, º) top
Sr1—O1i2.7998 (19)P1—O3ii1.509 (3)
Sr1—O1ii2.7998 (19)P1—O3v1.509 (3)
Sr1—O22.697 (4)P1—O51.5684 (19)
Sr1—O32.747 (3)P2—Mg2iv2.834 (2)
Sr1—O3iii2.747 (3)P2—Mg2xv2.834 (2)
Sr1—O4iv2.662 (4)P2—O21.541 (4)
Sr1—O6i2.548 (3)P2—O4iv1.584 (5)
Sr1—O6v2.548 (3)P2—O61.504 (3)
Sr1—O6vi2.827 (3)P2—O6iii1.504 (3)
Sr1—O6vii2.827 (3)O1—Sr1ix2.7998 (19)
Sr2—O12.238 (4)O1—Sr1x2.7998 (19)
Sr2—O1ii2.238 (4)O1—Sr22.238 (4)
Sr2—O22.279 (3)O1—Mg12.238 (4)
Sr2—O2viii2.279 (3)O1—P11.487 (4)
Sr2—O2ix2.279 (3)O2—Sr12.697 (4)
Sr2—O2x2.279 (3)O2—Sr22.279 (3)
Sr2—O63.414 (3)O2—Sr2i2.279 (3)
Sr2—O6viii3.414 (3)O2—Mg12.279 (3)
Sr2—O6ii3.414 (3)O2—Mg1i2.279 (3)
Sr2—O6v3.414 (3)O2—P21.541 (4)
Mg1—O12.238 (4)O3—Sr12.747 (3)
Mg1—O1ii2.238 (4)O3—Mg21.931 (3)
Mg1—O22.279 (3)O3—P1ii1.509 (3)
Mg1—O2viii2.279 (3)O4—Sr1vi2.662 (4)
Mg1—O2ix2.279 (3)O4—Mg22.015 (2)
Mg1—O2x2.279 (3)O4—Mg2xvi2.015 (2)
Mg2—P2vi2.834 (2)O4—P2vi1.584 (5)
Mg2—P2xi2.834 (2)O5—P11.5684 (19)
Mg2—O31.931 (3)O5—P1xvii1.5684 (19)
Mg2—O3xii1.931 (3)O6—Sr1ix2.548 (3)
Mg2—O42.015 (2)O6—Sr1iv2.827 (3)
Mg2—O4xiii2.015 (2)O6—Sr23.414 (3)
Mg2—O6vi2.512 (3)O6—Mg2iv2.512 (3)
Mg2—O6xiv2.512 (3)O6—P21.504 (3)
P1—O11.487 (4)
O1i—Sr1—O1ii61.95 (13)O1—Mg1—O2x84.08 (13)
O1i—Sr1—O266.74 (12)O1ii—Mg1—O284.08 (13)
O1i—Sr1—O391.29 (10)O1ii—Mg1—O2viii84.08 (13)
O1i—Sr1—O3xviii52.72 (9)O1ii—Mg1—O2ix95.92 (13)
O1i—Sr1—O4iv114.01 (11)O1ii—Mg1—O2x95.92 (13)
O1i—Sr1—O6i71.43 (9)O2—Mg1—O2viii75.61 (16)
O1i—Sr1—O6v129.19 (10)O2—Mg1—O2ix104.39 (16)
O1i—Sr1—O6vi145.90 (11)O2—Mg1—O2x180.0
O1i—Sr1—O6xix111.99 (10)O2viii—Mg1—O2ix179.9802
O1ii—Sr1—O266.74 (12)O2viii—Mg1—O2x104.39 (16)
O1ii—Sr1—O352.72 (9)O2ix—Mg1—O2x75.61 (16)
O1ii—Sr1—O3xviii91.29 (10)O3—Mg2—O3xii108.7 (2)
O1ii—Sr1—O4iv114.01 (11)O3—Mg2—O4107.24 (14)
O1ii—Sr1—O6i129.19 (10)O3—Mg2—O4xiii101.93 (15)
O1ii—Sr1—O6v71.43 (9)O3xii—Mg2—O4101.93 (15)
O1ii—Sr1—O6vi111.99 (10)O3xii—Mg2—O4xiii107.24 (14)
O1ii—Sr1—O6xix145.90 (11)O4—Mg2—O4xiii128.8 (3)
O2—Sr1—O3118.58 (9)O1—P1—O3ii110.58 (17)
O2—Sr1—O3xviii118.58 (9)O1—P1—O3v110.58 (17)
O2—Sr1—O4iv55.77 (13)O1—P1—O5105.6 (3)
O2—Sr1—O6i77.54 (8)O3ii—P1—O3v112.9 (3)
O2—Sr1—O6v77.54 (8)O3ii—P1—O5108.4 (2)
O2—Sr1—O6vi145.12 (9)O3v—P1—O5108.4 (2)
O2—Sr1—O6xix145.12 (9)O2—P2—O4iv106.6 (3)
O3—Sr1—O3xviii75.21 (12)O2—P2—O6113.22 (17)
O3—Sr1—O4iv142.30 (6)O2—P2—O6xviii113.22 (17)
O3—Sr1—O6i150.15 (10)O4iv—P2—O6105.57 (16)
O3—Sr1—O6v74.96 (8)O4iv—P2—O6xviii105.57 (16)
O3—Sr1—O6vi64.44 (8)O6—P2—O6xviii111.9 (3)
O3—Sr1—O6xix96.12 (8)Sr1ix—O1—Sr1x117.05 (13)
O3xviii—Sr1—O4iv142.30 (6)Sr1ix—O1—Sr299.73 (11)
O3xviii—Sr1—O6i74.96 (8)Sr1ix—O1—Mg199.73 (11)
O3xviii—Sr1—O6v150.15 (10)Sr1ix—O1—P197.45 (13)
O3xviii—Sr1—O6vi96.12 (8)Sr1x—O1—Sr299.73 (11)
O3xviii—Sr1—O6xix64.44 (8)Sr1x—O1—Mg199.73 (11)
O4iv—Sr1—O6i67.41 (7)Sr1x—O1—P197.45 (13)
O4iv—Sr1—O6v67.41 (7)Sr2—O1—P1146.7 (3)
O4iv—Sr1—O6vi99.23 (11)Mg1—O1—P1146.7 (3)
O4iv—Sr1—O6xix99.23 (11)Sr1—O2—Sr2101.73 (13)
O6i—Sr1—O6v134.82 (14)Sr1—O2—Sr2i101.73 (13)
O6i—Sr1—O6vi117.91 (7)Sr1—O2—Mg1101.73 (13)
O6i—Sr1—O6xix69.77 (10)Sr1—O2—Mg1i101.73 (13)
O6v—Sr1—O6vi69.77 (10)Sr1—O2—P298.7 (2)
O6v—Sr1—O6xix117.91 (7)Sr2—O2—Sr2i104.32 (16)
O6vi—Sr1—O6xix52.31 (12)Sr2—O2—Mg1i104.32 (16)
O1—Sr2—O1ii179.9657Sr2—O2—P2122.79 (12)
O1—Sr2—O295.92 (13)Sr2i—O2—Mg1104.32 (16)
O1—Sr2—O2viii95.92 (13)Sr2i—O2—P2122.79 (12)
O1—Sr2—O2ix84.08 (13)Mg1—O2—Mg1i104.32 (16)
O1—Sr2—O2x84.08 (13)Mg1—O2—P2122.79 (12)
O1ii—Sr2—O284.08 (13)Mg1i—O2—P2122.79 (12)
O1ii—Sr2—O2viii84.08 (13)Sr1—O3—Mg2110.35 (13)
O1ii—Sr2—O2ix95.92 (13)Sr1—O3—P1ii99.10 (16)
O1ii—Sr2—O2x95.92 (13)Mg2—O3—P1ii150.5 (2)
O2—Sr2—O2viii75.61 (16)Sr1vi—O4—Mg2110.29 (12)
O2—Sr2—O2ix104.39 (16)Sr1vi—O4—Mg2xvi110.29 (12)
O2—Sr2—O2x180.0Sr1vi—O4—P2vi98.9 (2)
O2viii—Sr2—O2ix179.9802Mg2—O4—Mg2xvi126.5 (3)
O2viii—Sr2—O2x104.39 (16)Mg2—O4—P2vi103.25 (15)
O2ix—Sr2—O2x75.61 (16)Mg2xvi—O4—P2vi103.25 (15)
O1—Mg1—O1ii179.9657P1—O5—P1xx163.2 (5)
O1—Mg1—O295.92 (13)Sr1ix—O6—Sr1iv110.23 (10)
O1—Mg1—O2viii95.92 (13)Sr1ix—O6—P2155.0 (2)
O1—Mg1—O2ix84.08 (13)Sr1iv—O6—P293.78 (16)
Symmetry codes: (i) x, y+1, z+1/2; (ii) x, y+1, z; (iii) x, y, z+1/2; (iv) x+1/2, y+1/2, z; (v) x, y+1, z; (vi) x+1/2, y1/2, z; (vii) x1/2, y3/2, z+1/2; (viii) x, y, z; (ix) x, y+1, z1/2; (x) x, y+1, z1/2; (xi) x+1/2, y+1/2, z1/2; (xii) x, y, z; (xiii) x, y, z1/2; (xiv) x1/2, y1/2, z; (xv) x+1/2, y+1/2, z+1/2; (xvi) x, y, z+1/2; (xvii) x, y, z+1/2; (xviii) x, y, z+3/2; (xix) x+1/2, y1/2, z+3/2; (xx) x1, y1, z+1/2.
(phase_2) dimagnesium heptaoxidodiphosphate top
Crystal data top
Mg2P2O7Z = 4
Mr = 222.56F(000) = 440.0
Monoclinic, P21/cDx = 3.105 Mg m3
Hall symbol: -P 2ybcCu Kα1 radiation, λ = 1.5406 Å
a = 6.9443 (4) ÅT = 296 K
b = 8.2861 (4) Åwhite
c = 9.0438 (5) Åflat sheet, 20 × 20 mm
β = 113.816 (3)°Specimen preparation: Prepared at 296 K
V = 476.08 (5) Å3
Data collection top
Bruker D8 Advance
diffractometer
Data collection mode: reflection
Radiation source: sealed X-ray tube, Bruker Cu Ceramic X-ray tubeScan method: step
Ge 111 monochromator2θmin = 8.0°, 2θmax = 140.422°, 2θstep = 0.017°
Specimen mounting: packed powder pellet
Refinement top
Least-squares matrix: full7939 data points
Rp = 0.048Profile function: CW Profile function number 4 with 21 terms Pseudovoigt profile coefficients as parameterized in Thompson et al. [Thompson, P., Cox, D. E. & Hastings, J. B. (1987). J. Appl. Cryst. 20, 79–83]. Asymmetry correction of Finger et al. [Finger, L. W., Cox, D. E. & Jephcoat, A. P. (1994). J. Appl. Cryst. 27, 892–900]. Microstrain broadening by Stephens [Stephens, P. W. (1999). J. Appl. Cryst. 32, 281–289]. #1(GU) = 178.981 #2(GV) = -107.291 #3(GW) = 12.592 #4(GP) = 19.425 #5(LX) = 3.011 #6(ptec) = 0.00 #7(trns) = 0.00 #8(shft) = 3.1799 #9(sfec) = 0.00 #10(S/L) = 0.0005 #11(H/L) = 0.0005 #12(eta) = 0.7500 #13(S400 ) = 0.0E+00 #14(S040 ) = 0.0E+00 #15(S004 ) = 0.0E+00 #16(S220 ) = 0.0E+00 #17(S202 ) = 0.0E+00 #18(S022 ) = 0.0E+00 #19(S301 ) = 0.0E+00 #20(S103 ) = 0.0E+00 #21(S121 ) = 0.0E+00 Peak tails are ignored where the intensity is below 0.0020 times the peak Aniso. broadening axis 0.0 0.0 1.0
Rwp = 0.06381 parameters
Rexp = 0.0250 restraints
RBragg = 0.047Weighting scheme based on measured s.u.'s
R(F) = 0.047(Δ/σ)max = 0.02
R(F2) = 0.04372Background function: GSAS Background function number 1 with 36 terms. Shifted Chebyshev function of 1st kind 1: 667.815 2: -121.026 3: 250.928 4: -108.029 5: 130.095 6: -120.393 7: 81.5238 8: -66.4354 9: 31.4946 10: -19.2674 11: 16.0150 12: -21.1906 13: 24.6787 14: -7.73173 15: 5.82669 16: 7.16351 17: 9.66948 18: 8.02466 19: 5.65618 20: 4.74674 21: -11.8793 22: -0.873263 23: -2.40368 24: -9.55052 25: -6.36605 26: 6.28370 27: -8.07052 28: 6.33955 29: -12.6008 30: 3.68005 31: 5.95000 32: 7.62516 33: 1.58465 34: 5.63269 35: -2.90398 36: 14.7130
χ2 = 6.250
Crystal data top
Mg2P2O7β = 113.816 (3)°
Mr = 222.56V = 476.08 (5) Å3
Monoclinic, P21/cZ = 4
a = 6.9443 (4) ÅCu Kα1 radiation, λ = 1.5406 Å
b = 8.2861 (4) ÅT = 296 K
c = 9.0438 (5) Åflat sheet, 20 × 20 mm
Data collection top
Bruker D8 Advance
diffractometer
Scan method: step
Specimen mounting: packed powder pellet2θmin = 8.0°, 2θmax = 140.422°, 2θstep = 0.017°
Data collection mode: reflection
Refinement top
Rp = 0.048R(F2) = 0.04372
Rwp = 0.063χ2 = 6.250
Rexp = 0.0257939 data points
RBragg = 0.04781 parameters
R(F) = 0.0470 restraints
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
Mg10.249570.924910.121180.02084*
Mg20.698610.433110.828590.02084*
P10.947850.764380.764930.02084*
P20.524510.772970.468340.02084*
O10.729020.832620.590140.02084*
O20.376230.761090.551270.02084*
O31.127560.769090.699860.02084*
O41.011290.907110.895330.02084*
O50.923640.59630.828740.02084*
O60.470960.897280.320330.02084*
O70.599830.606010.41920.02084*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
???????
Geometric parameters (Å, º) top
Mg1—O2i1.9994 (1)O1—P11.7854 (1)
Mg1—O3ii2.0725 (1)O1—P21.4870 (1)
Mg1—O4iii2.0499 (1)O2—Mg1viii1.9994 (1)
Mg1—O4iv2.2412 (1)O2—Mg2x1.9845 (1)
Mg1—O61.8503 (1)O2—P21.5021 (1)
Mg1—O7v1.9461 (1)O3—Mg1xi2.0725 (1)
Mg2—O2vi1.9845 (1)O3—Mg2xii1.9030 (1)
Mg2—O3vii1.9030 (1)O3—P11.5806 (1)
Mg2—O52.0661 (1)O4—Mg1xiii2.0499 (1)
Mg2—O6viii2.0939 (1)O4—Mg1iv2.2412 (1)
Mg2—O7ix2.3814 (1)O4—P11.6013 (1)
P1—O11.7854 (1)O5—Mg22.0661 (1)
P1—O31.5806 (1)O5—P11.5425 (1)
P1—O41.6013 (1)O6—Mg11.8503 (1)
P1—O51.5425 (1)O6—Mg2i2.0939 (1)
P2—O11.4870 (1)O6—P21.6091 (1)
P2—O21.5021 (1)O7—Mg1xiv1.9461 (1)
P2—O61.6091 (1)O7—Mg2ix2.3814 (1)
P2—O71.6040 (1)O7—P21.6040 (1)
O2xv—Mg1—O3xvi78.680 (4)O1—P1—O5115.771 (2)
O2xv—Mg1—O4iii84.872 (3)O3—P1—O4103.426 (3)
O2xv—Mg1—O4iv154.7676 (11)O3—P1—O5112.5380 (13)
O2xv—Mg1—O685.052 (3)O4—P1—O5115.496 (4)
O2xv—Mg1—O7v101.344 (4)O1—P2—O2107.107 (5)
O3xvi—Mg1—O4iii90.507 (3)O1—P2—O6103.548 (3)
O3xvi—Mg1—O4iv94.190 (4)O1—P2—O799.856 (3)
O3xvi—Mg1—O682.185 (3)O2—P2—O6118.856 (3)
O3xvi—Mg1—O7v171.0005 (5)O2—P2—O7116.6010 (19)
O4iii—Mg1—O4iv70.899 (3)O6—P2—O7108.259 (4)
O4iii—Mg1—O6168.5470 (8)P1—O1—P2140.125 (3)
O4iii—Mg1—O7v98.467 (3)Mg1xv—O2—Mg2x97.738 (4)
O4iv—Mg1—O6118.245 (3)Mg1xviii—O2—P2133.3317 (16)
O4iv—Mg1—O7v89.414 (4)Mg2x—O2—P2127.599 (2)
O6—Mg1—O7v88.844 (3)Mg1xix—O3—Mg2xii97.926 (4)
O2vi—Mg2—O3vii83.208 (4)Mg1xx—O3—P1127.0411 (19)
O2vi—Mg2—O5146.6086 (16)Mg2xii—O3—P1135.016 (2)
O2vi—Mg2—O6xvii98.094 (4)Mg1xiii—O4—Mg1iv109.101 (3)
O2vi—Mg2—O7ix95.548 (4)Mg1xiii—O4—P1131.173 (2)
O3vii—Mg2—O586.937 (4)Mg1iv—O4—P1115.787 (3)
O3vii—Mg2—O6xvii170.2380 (6)Mg2—O5—P1141.9393 (17)
O3vii—Mg2—O7ix97.705 (4)Mg1—O6—Mg2xxi105.681 (3)
O5—Mg2—O6xvii96.931 (4)Mg1—O6—P2135.320 (2)
O5—Mg2—O7ix117.404 (3)Mg2xxii—O6—P2118.845 (3)
O6xvii—Mg2—O7ix72.552 (3)Mg1xiv—O7—Mg2ix92.744 (3)
O1—P1—O3100.385 (5)Mg1xiv—O7—P2167.7228 (6)
O1—P1—O4107.510 (3)Mg2ix—O7—P296.943 (3)
Symmetry codes: (i) x, y+3/2, z1/2; (ii) x1, y+3/2, z1/2; (iii) x1, y, z1; (iv) x+1, y+2, z+1; (v) x+1, y+1/2, z+1/2; (vi) x+1, y1/2, z+3/2; (vii) x+2, y1/2, z+3/2; (viii) x, y+3/2, z+1/2; (ix) x+1, y+1, z+1; (x) x+1, y+1/2, z+3/2; (xi) x+1, y+3/2, z+1/2; (xii) x+2, y+1/2, z+3/2; (xiii) x+1, y, z+1; (xiv) x+1, y1/2, z+1/2; (xv) x, y+5/2, z+1/2; (xvi) x1, y+5/2, z+1/2; (xvii) x, y+5/2, z+3/2; (xviii) x1, y+3/2, z+3/2; (xix) x+1, y+5/2, z+1/2; (xx) x, y+3/2, z+3/2; (xxi) x, y+5/2, z1/2; (xxii) x1, y+3/2, z+1/2.
(phase_3) trimagnesium ocyaoxidodiphosphate top
Crystal data top
Mg3P2O8Z = 2
Mr = 262.87F(000) = 260.0
Monoclinic, P21/nDx = 2.745 Mg m3
Hall symbol: -P 2ynCu Kα1 radiation, λ = 1.5406 Å
a = 7.594 (3) ÅT = 296 K
b = 8.282 (8) Åwhite
c = 5.071 (4) Åflat sheet, 20 × 20 mm
β = 94.01 (6)°Specimen preparation: Prepared at 296 K
V = 318.1 (4) Å3
Data collection top
Bruker D8 Advance
diffractometer
Data collection mode: reflection
Radiation source: sealed X-ray tube, Bruker Cu Ceramic X-ray tubeScan method: step
Ge 111 monochromator2θmin = 8.0°, 2θmax = 140.422°, 2θstep = 0.017°
Specimen mounting: packed powder pellet
Refinement top
Least-squares matrix: full7939 data points
Rp = 0.048Profile function: CW Profile function number 4 with 21 terms Pseudovoigt profile coefficients as parameterized in Thompson et al. [Thompson, P., Cox, D. E. & Hastings, J. B. (1987). J. Appl. Cryst. 20, 79–83]. Asymmetry correction of Finger et al. [Finger, L. W., Cox, D. E. & Jephcoat, A. P. (1994). J. Appl. Cryst. 27, 892–900]. Microstrain broadening by Stephens [Stephens, P. W. (1999). J. Appl. Cryst. 32, 281–289]. #1(GU) = 0.000 #2(GV) = 61.116 #3(GW) = -3.576 #4(GP) = 8.238 #5(LX) = 9.783 #6(ptec) = 0.00 #7(trns) = 0.00 #8(shft) = 3.1799 #9(sfec) = 0.00 #10(S/L) = 0.0005 #11(H/L) = 0.0005 #12(eta) = 0.7500 #13(S400 ) = 0.0E+00 #14(S040 ) = 0.0E+00 #15(S004 ) = 0.0E+00 #16(S220 ) = 0.0E+00 #17(S202 ) = 0.0E+00 #18(S022 ) = 0.0E+00 #19(S301 ) = 0.0E+00 #20(S103 ) = 0.0E+00 #21(S121 ) = 0.0E+00 Peak tails are ignored where the intensity is below 0.0020 times the peak Aniso. broadening axis 0.0 0.0 1.0
Rwp = 0.06381 parameters
Rexp = 0.0250 restraints
RBragg = 0.047Weighting scheme based on measured s.u.'s
R(F) = 0.049(Δ/σ)max = 0.02
R(F2) = 0.04372Background function: GSAS Background function number 1 with 36 terms. Shifted Chebyshev function of 1st kind 1: 667.815 2: -121.026 3: 250.928 4: -108.029 5: 130.095 6: -120.393 7: 81.5238 8: -66.4354 9: 31.4946 10: -19.2674 11: 16.0150 12: -21.1906 13: 24.6787 14: -7.73173 15: 5.82669 16: 7.16351 17: 9.66948 18: 8.02466 19: 5.65618 20: 4.74674 21: -11.8793 22: -0.873263 23: -2.40368 24: -9.55052 25: -6.36605 26: 6.28370 27: -8.07052 28: 6.33955 29: -12.6008 30: 3.68005 31: 5.95000 32: 7.62516 33: 1.58465 34: 5.63269 35: -2.90398 36: 14.7130
χ2 = 6.250
Crystal data top
Mg3P2O8β = 94.01 (6)°
Mr = 262.87V = 318.1 (4) Å3
Monoclinic, P21/nZ = 2
a = 7.594 (3) ÅCu Kα1 radiation, λ = 1.5406 Å
b = 8.282 (8) ÅT = 296 K
c = 5.071 (4) Åflat sheet, 20 × 20 mm
Data collection top
Bruker D8 Advance
diffractometer
Scan method: step
Specimen mounting: packed powder pellet2θmin = 8.0°, 2θmax = 140.422°, 2θstep = 0.017°
Data collection mode: reflection
Refinement top
Rp = 0.048R(F2) = 0.04372
Rwp = 0.063χ2 = 6.250
Rexp = 0.0257939 data points
RBragg = 0.04781 parameters
R(F) = 0.0490 restraints
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
Mg10.60950.14320.0920.015*
Mg20.00.00.50.015*
P10.19960.19460.03550.015*
O10.05890.14460.81880.015*
O20.12620.19950.30360.015*
O30.25920.36290.9470.015*
O40.35450.07590.04590.015*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
???????
Geometric parameters (Å, º) top
Mg1—O1i2.1496 (14)P1—O41.5310 (7)
Mg1—O2i1.9692 (11)O1—Mg1vii2.1496 (14)
Mg1—O3i2.0613 (16)O1—Mg22.0363 (12)
Mg1—O42.0128 (9)O1—P1viii1.5350 (11)
Mg1—O4ii1.9706 (16)O2—Mg1vii1.9692 (11)
Mg2—O12.0363 (12)O2—Mg22.1849 (13)
Mg2—O1iii2.0363 (12)O2—P11.5055 (11)
Mg2—O22.1849 (13)O3—Mg1vii2.0613 (16)
Mg2—O2iii2.1849 (13)O3—Mg2ix2.1532 (9)
Mg2—O3iv2.1532 (9)O3—P1viii1.5419 (12)
Mg2—O3v2.1532 (9)O4—Mg12.0128 (9)
P1—O1vi1.5350 (11)O4—Mg1ii1.9706 (16)
P1—O21.5055 (11)O4—P11.5310 (7)
P1—O3vi1.5419 (12)
O1i—Mg1—O2i83.09 (6)O2iii—Mg2—O3iv86.56 (5)
O1i—Mg1—O3i70.19 (3)O2iii—Mg2—O3v93.44 (5)
O1x—Mg1—O494.70 (4)O3iv—Mg2—O3v180.0
O1x—Mg1—O4ii167.723 (8)O1vi—P1—O2111.75 (5)
O2i—Mg1—O3i127.20 (3)O1vi—P1—O3vi103.84 (3)
O2x—Mg1—O4102.03 (5)O1vi—P1—O4110.24 (4)
O2x—Mg1—O4ii109.14 (6)O2—P1—O3vi111.91 (3)
O3x—Mg1—O4124.19 (5)O2—P1—O4108.56 (4)
O3x—Mg1—O4ii101.87 (2)O3vi—P1—O4110.49 (5)
O4—Mg1—O4ii81.95 (3)Mg1xi—O1—Mg295.37 (6)
O1—Mg2—O1iii180.0Mg1xii—O1—P1viii91.20 (4)
O1—Mg2—O280.69 (6)Mg2—O1—P1viii146.12 (2)
O1—Mg2—O2iii99.31 (6)Mg1xi—O2—Mg296.24 (6)
O1—Mg2—O3iv94.22 (6)Mg1xii—O2—P1137.36 (3)
O1—Mg2—O3v85.78 (6)Mg2—O2—P1126.38 (3)
O1iii—Mg2—O299.31 (6)Mg1xi—O3—Mg2ix122.25 (4)
O1iii—Mg2—O2iii80.69 (6)Mg1xii—O3—P1viii94.41 (2)
O1iii—Mg2—O3iv85.78 (6)Mg2ix—O3—P1viii134.78 (3)
O1iii—Mg2—O3v94.22 (6)Mg1—O4—Mg1ii98.05 (3)
O2—Mg2—O2iii179.9802Mg1—O4—P1123.83 (4)
O2—Mg2—O3iv93.44 (5)Mg1ii—O4—P1134.78 (3)
O2—Mg2—O3v86.56 (5)
Symmetry codes: (i) x+1/2, y+1/2, z1/2; (ii) x+1, y, z; (iii) x, y, z+1; (iv) x+1/2, y1/2, z+3/2; (v) x1/2, y+1/2, z1/2; (vi) x, y, z1; (vii) x1/2, y+1/2, z+1/2; (viii) x, y, z+1; (ix) x+1/2, y+1/2, z+3/2; (x) x+3/2, y+3/2, z+1/2; (xi) x+1/2, y+3/2, z+1/2; (xii) x1/2, y+1/2, z+3/2.

Experimental details

(phase_1)(phase_2)(phase_3)
Crystal data
Chemical formulaSr2.36Mg2.64P4O15Mg2P2O7Mg3P2O8
Mr634.65222.56262.87
Crystal system, space groupOrthorhombic, CmcmMonoclinic, P21/cMonoclinic, P21/n
Temperature (K)296296296
a, b, c (Å)14.27366 (9), 11.75678 (7), 7.19753 (4)6.9443 (4), 8.2861 (4), 9.0438 (5)7.594 (3), 8.282 (8), 5.071 (4)
α, β, γ (°)90, 90, 9090, 113.816 (3), 9090, 94.01 (6), 90
V3)1207.83 (1)476.08 (5)318.1 (4)
Z442
Radiation typeCu Kα1, λ = 1.5406 ÅCu Kα1, λ = 1.5406 ÅCu Kα1, λ = 1.5406 Å
Specimen shape, size (mm)Flat sheet, 20 × 20Flat sheet, 20 × 20Flat sheet, 20 × 20
Data collection
DiffractometerBruker D8 Advance
diffractometer
Bruker D8 Advance
diffractometer
Bruker D8 Advance
diffractometer
Specimen mountingPacked powder pelletPacked powder pelletPacked powder pellet
Data collection modeReflectionReflectionReflection
Scan methodStepStepStep
2θ values (°)2θmin = 8.0 2θmax = 140.422 2θstep = 0.0172θmin = 8.0 2θmax = 140.422 2θstep = 0.0172θmin = 8.0 2θmax = 140.422 2θstep = 0.017
Refinement
R factors and goodness of fitRp = 0.048, Rwp = 0.063, Rexp = 0.025, RBragg = 0.047, R(F) = 0.028, R(F2) = 0.04372, χ2 = 6.250Rp = 0.048, Rwp = 0.063, Rexp = 0.025, RBragg = 0.047, R(F) = 0.047, R(F2) = 0.04372, χ2 = 6.250Rp = 0.048, Rwp = 0.063, Rexp = 0.025, RBragg = 0.047, R(F) = 0.049, R(F2) = 0.04372, χ2 = 6.250
No. of data points793979397939
No. of parameters818181

Computer programs: COMMANDER (Bruker, 2003), GSAS (Larson & Von Dreele, 2000), EVA (Bruker, 2003), SHELXS (Sheldrick, 2008) and CRYSTALS (Betteridge et al., 2003), ATOMS (Dowty, 2000).

 

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