Acta Cryst. (2009). E65, i58 [ doi:10.1107/S1600536809025434 ]
Caesium magnesium orthophosphate is built up from MgO4 and PO4 tetrahedra (both with . m. symmetry) linked together by corners, forming a three-dimensional framework. The Cs atoms have .m. site symmetry and are located in hexagonal channels running along the a- and b-axis directions.
In the course of investigating the Cs2O–MgO–Bi2O3–P2O5 system, the starting components CsPO3 (3.0 g), MgO (0.113 g) and Bi2O3 (0.652 g) were finely ground and melted in a platinum crucible at 1273 K. The melt was kept at this temperature over 2 h to reach homogeneity and then cooled at a rate of 30 K h-1 to 993 K. After the melt was cooled to room temperature and treated with a small amount of deionized water, colorless needle-shaped crystals were isolated. X-ray powder diffraction showed that CsMgPO4 is the only crystalline product.
Data collection: CrysAlis CCD (Oxford Diffraction, 2006); cell refinement: CrysAlis CCD (Oxford Diffraction, 2006); data reduction: CrysAlis RED (Oxford Diffraction, 2006); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 1999); software used to prepare material for publication: WinGX (Farrugia, 1999) and enCIFer (Allen et al., 2004).
![[Figure 1]](./mg2075fig1thm.gif)
| Fig. 1. View of CsMgPO4 with displacement ellipsoids at the 50% probability level. |
![[Figure 2]](./mg2075fig2thm.gif)
| Fig. 2. Formation of hexagonal channels along a and b directions in CsMgPO4 (PO4, pink; MgO4, yellow; Cs, blue). |
| CsMgPO4 | F000 = 456 |
| Mr = 252.19 | Dx = 3.516 Mg m−3 |
| Orthorhombic, Pnma | Mo Kα radiation, λ = 0.71073 Å |
| Hall symbol: -P 2ac 2n | Cell parameters from 8753 reflections |
| a = 8.9327 (2) Å | θ = 3.1–35.0º |
| b = 5.5277 (2) Å | µ = 8.13 mm−1 |
| c = 9.6487 (3) Å | T = 293 K |
| V = 476.43 (3) Å3 | Prism, colorless |
| Z = 4 | 0.12 × 0.10 × 0.08 mm |
| Oxford Diffraction Xcalibur-3 diffractometer | 1137 independent reflections |
| Radiation source: fine-focus sealed tube | 874 reflections with I > 2σ(I) |
| Monochromator: graphite | Rint = 0.027 |
| T = 293 K | θmax = 35.0º |
| φ and ω scans | θmin = 3.1º |
| Absorption correction: multi-scan (Blessing, 1995) | h = −14→14 |
| Tmin = 0.413, Tmax = 0.503 | k = −8→8 |
| 8753 measured reflections | l = −15→15 |
| Refinement on F2 | Secondary atom site location: difference Fourier map |
| Least-squares matrix: full | w = 1/[σ2(Fo2) + (0.0265P)2] where P = (Fo2 + 2Fc2)/3 |
| R[F2 > 2σ(F2)] = 0.021 | (Δ/σ)max = 0.018 |
| wR(F2) = 0.047 | Δρmax = 1.23 e Å−3 |
| S = 1.00 | Δρmin = −1.02 e Å−3 |
| 1137 reflections | Extinction correction: SHELXL97 (Sheldrick, 2008) |
| 41 parameters | Extinction coefficient: 0.0211 (4) |
| Primary atom site location: structure-invariant direct methods |
| CsMgPO4 | V = 476.43 (3) Å3 |
| Mr = 252.19 | Z = 4 |
| Orthorhombic, Pnma | Mo Kα |
| a = 8.9327 (2) Å | µ = 8.13 mm−1 |
| b = 5.5277 (2) Å | T = 293 K |
| c = 9.6487 (3) Å | 0.12 × 0.10 × 0.08 mm |
| Oxford Diffraction Xcalibur-3 diffractometer | 1137 independent reflections |
| Absorption correction: multi-scan (Blessing, 1995) | 874 reflections with I > 2σ(I) |
| Tmin = 0.413, Tmax = 0.503 | Rint = 0.027 |
| 8753 measured reflections |
| R[F2 > 2σ(F2)] = 0.021 | 41 parameters |
| wR(F2) = 0.047 | Δρmax = 1.23 e Å−3 |
| S = 1.00 | Δρmin = −1.02 e Å−3 |
| 1137 reflections |
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. |
| x | y | z | Uiso*/Ueq | ||
| Cs1 | 0.497176 (11) | 0.25 | 0.703332 (10) | 0.02472 (2) | |
| Mg1 | 0.32166 (5) | 0.25 | 0.08109 (5) | 0.01434 (11) | |
| P1 | 0.20302 (4) | 0.25 | 0.41474 (4) | 0.01345 (7) | |
| O1 | 0.26034 (19) | 0.25 | 0.26799 (13) | 0.0590 (6) | |
| O2 | 0.26291 (11) | 0.02604 (13) | 0.48850 (9) | 0.0328 (2) | |
| O3 | 0.03356 (14) | 0.25 | 0.41501 (19) | 0.0345 (4) |
| U11 | U22 | U33 | U12 | U13 | U23 | |
| Cs1 | 0.02161 (4) | 0.02632 (5) | 0.02623 (4) | 0 | −0.00031 (4) | 0 |
| Mg1 | 0.01301 (19) | 0.0133 (2) | 0.0168 (2) | 0 | 0.00166 (17) | 0 |
| P1 | 0.01272 (13) | 0.01259 (14) | 0.01505 (14) | 0 | 0.00207 (12) | 0 |
| O1 | 0.0594 (11) | 0.1014 (17) | 0.0162 (7) | 0 | 0.0121 (7) | 0 |
| O2 | 0.0239 (4) | 0.0190 (4) | 0.0555 (6) | −0.0002 (3) | −0.0016 (4) | 0.0156 (4) |
| O3 | 0.0121 (4) | 0.0286 (6) | 0.0629 (10) | 0 | −0.0003 (6) | 0 |
| Cs1—O2 | 3.1951 (9) | Mg1—Cs1xiii | 4.1402 (4) |
| Cs1—O2i | 3.1951 (9) | P1—O1 | 1.5056 (13) |
| Cs1—O2ii | 3.2166 (9) | P1—O3 | 1.5138 (13) |
| Cs1—O2iii | 3.2166 (9) | P1—O2i | 1.5249 (8) |
| Cs1—O3iv | 3.4476 (11) | P1—O2 | 1.5249 (8) |
| Cs1—O3v | 3.4476 (11) | P1—Cs1ix | 3.8727 (3) |
| Cs1—O1vi | 3.5224 (11) | P1—Cs1xiii | 3.8727 (3) |
| Cs1—O1ii | 3.5224 (11) | P1—Cs1vi | 4.0136 (3) |
| Cs1—O1v | 3.6496 (11) | P1—Cs1ii | 4.0136 (3) |
| Cs1—O1iv | 3.6496 (11) | P1—Cs1xiv | 4.1184 (4) |
| Cs1—O3vii | 3.6968 (18) | O1—Cs1vi | 3.5224 (11) |
| Cs1—Mg1vi | 3.8189 (4) | O1—Cs1ii | 3.5224 (11) |
| Mg1—O1 | 1.8847 (13) | O1—Cs1ix | 3.6496 (11) |
| Mg1—O3viii | 1.8932 (13) | O1—Cs1xiii | 3.6496 (11) |
| Mg1—O2ix | 1.9228 (8) | O2—Mg1v | 1.9228 (8) |
| Mg1—O2x | 1.9228 (8) | O2—Cs1ii | 3.2166 (9) |
| Mg1—Cs1vi | 3.8189 (4) | O3—Mg1xii | 1.8932 (13) |
| Mg1—Cs1ii | 3.8189 (4) | O3—Cs1ix | 3.4476 (11) |
| Mg1—Cs1xi | 3.9678 (5) | O3—Cs1xiii | 3.4476 (11) |
| Mg1—Cs1xii | 3.9916 (5) | O3—Cs1xiv | 3.6968 (18) |
| Mg1—Cs1ix | 4.1402 (4) | ||
| O2—Cs1—O2i | 45.59 (3) | O1—Mg1—Cs1ix | 61.80 (3) |
| O2—Cs1—O2ii | 83.06 (3) | O3viii—Mg1—Cs1ix | 133.01 (2) |
| O2i—Cs1—O2ii | 104.291 (19) | O2ix—Mg1—Cs1ix | 48.11 (3) |
| O2—Cs1—O2iii | 104.291 (19) | O2x—Mg1—Cs1ix | 113.07 (3) |
| O2i—Cs1—O2iii | 83.06 (3) | Cs1vi—Mg1—Cs1ix | 128.277 (13) |
| O2ii—Cs1—O2iii | 56.64 (3) | Cs1ii—Mg1—Cs1ix | 69.709 (5) |
| O2—Cs1—O3iv | 130.00 (3) | Cs1xi—Mg1—Cs1ix | 122.243 (9) |
| O2i—Cs1—O3iv | 91.24 (3) | Cs1xii—Mg1—Cs1ix | 72.323 (7) |
| O2ii—Cs1—O3iv | 140.73 (3) | O1—Mg1—Cs1xiii | 61.80 (3) |
| O2iii—Cs1—O3iv | 90.78 (3) | O3viii—Mg1—Cs1xiii | 133.01 (2) |
| O2—Cs1—O3v | 91.24 (3) | O2ix—Mg1—Cs1xiii | 113.07 (3) |
| O2i—Cs1—O3v | 130.00 (3) | O2x—Mg1—Cs1xiii | 48.11 (3) |
| O2ii—Cs1—O3v | 90.78 (3) | Cs1vi—Mg1—Cs1xiii | 69.709 (5) |
| O2iii—Cs1—O3v | 140.73 (3) | Cs1ii—Mg1—Cs1xiii | 128.277 (14) |
| O3iv—Cs1—O3v | 106.58 (5) | Cs1xi—Mg1—Cs1xiii | 122.243 (9) |
| O2—Cs1—O1vi | 139.27 (2) | Cs1xii—Mg1—Cs1xiii | 72.323 (7) |
| O2i—Cs1—O1vi | 98.61 (3) | Cs1ix—Mg1—Cs1xiii | 83.758 (9) |
| O2ii—Cs1—O1vi | 90.44 (3) | O1—P1—O3 | 109.98 (10) |
| O2iii—Cs1—O1vi | 42.55 (2) | O1—P1—O2i | 108.64 (5) |
| O3iv—Cs1—O1vi | 51.20 (3) | O3—P1—O2i | 110.49 (5) |
| O3v—Cs1—O1vi | 129.16 (3) | O1—P1—O2 | 108.64 (5) |
| O2—Cs1—O1ii | 98.61 (3) | O3—P1—O2 | 110.49 (5) |
| O2i—Cs1—O1ii | 139.27 (2) | O2i—P1—O2 | 108.56 (7) |
| O2ii—Cs1—O1ii | 42.55 (2) | O1—P1—Cs1 | 116.78 (7) |
| O2iii—Cs1—O1ii | 90.44 (3) | O3—P1—Cs1 | 133.24 (7) |
| O3iv—Cs1—O1ii | 129.16 (3) | O2i—P1—Cs1 | 54.54 (3) |
| O3v—Cs1—O1ii | 51.20 (3) | O2—P1—Cs1 | 54.54 (3) |
| O1vi—Cs1—O1ii | 103.38 (4) | O1—P1—Cs1ix | 70.23 (4) |
| O2—Cs1—O1v | 53.46 (2) | O3—P1—Cs1ix | 62.56 (4) |
| O2i—Cs1—O1v | 89.52 (3) | O2i—P1—Cs1ix | 170.83 (4) |
| O2ii—Cs1—O1v | 99.15 (2) | O2—P1—Cs1ix | 80.12 (3) |
| O2iii—Cs1—O1v | 151.35 (2) | Cs1—P1—Cs1ix | 134.428 (4) |
| O3iv—Cs1—O1v | 117.11 (3) | O1—P1—Cs1xiii | 70.23 (4) |
| O3v—Cs1—O1v | 40.66 (3) | O3—P1—Cs1xiii | 62.56 (4) |
| O1vi—Cs1—O1v | 165.554 (5) | O2i—P1—Cs1xiii | 80.12 (3) |
| O1ii—Cs1—O1v | 77.288 (3) | O2—P1—Cs1xiii | 170.83 (4) |
| O2—Cs1—O1iv | 89.52 (3) | Cs1—P1—Cs1xiii | 134.428 (4) |
| O2i—Cs1—O1iv | 53.46 (2) | Cs1ix—P1—Cs1xiii | 91.069 (8) |
| O2ii—Cs1—O1iv | 151.35 (2) | O1—P1—Cs1vi | 60.41 (4) |
| O2iii—Cs1—O1iv | 99.15 (2) | O3—P1—Cs1vi | 131.89 (3) |
| O3iv—Cs1—O1iv | 40.66 (3) | O2i—P1—Cs1vi | 48.65 (4) |
| O3v—Cs1—O1iv | 117.11 (3) | O2—P1—Cs1vi | 117.22 (4) |
| O1vi—Cs1—O1iv | 77.288 (3) | Cs1—P1—Cs1vi | 75.434 (6) |
| O1ii—Cs1—O1iv | 165.554 (5) | Cs1ix—P1—Cs1vi | 130.546 (10) |
| O1v—Cs1—O1iv | 98.45 (4) | Cs1xiii—P1—Cs1vi | 70.558 (4) |
| O2—Cs1—O3vii | 134.74 (2) | O1—P1—Cs1ii | 60.41 (4) |
| O2i—Cs1—O3vii | 134.74 (2) | O3—P1—Cs1ii | 131.89 (3) |
| O2ii—Cs1—O3vii | 120.97 (2) | O2i—P1—Cs1ii | 117.22 (4) |
| O2iii—Cs1—O3vii | 120.97 (2) | O2—P1—Cs1ii | 48.65 (4) |
| O3iv—Cs1—O3vii | 54.33 (3) | Cs1—P1—Cs1ii | 75.434 (6) |
| O3v—Cs1—O3vii | 54.33 (3) | Cs1ix—P1—Cs1ii | 70.558 (4) |
| O1vi—Cs1—O3vii | 82.40 (2) | Cs1xiii—P1—Cs1ii | 130.546 (10) |
| O1ii—Cs1—O3vii | 82.40 (2) | Cs1vi—P1—Cs1ii | 87.043 (8) |
| O1v—Cs1—O3vii | 83.40 (2) | O1—P1—Cs1xiv | 173.36 (7) |
| O1iv—Cs1—O3vii | 83.40 (2) | O3—P1—Cs1xiv | 63.38 (7) |
| O2—Cs1—Mg1vi | 155.689 (15) | O2i—P1—Cs1xiv | 74.87 (4) |
| O2i—Cs1—Mg1vi | 110.517 (14) | O2—P1—Cs1xiv | 74.87 (4) |
| O2ii—Cs1—Mg1vi | 111.987 (18) | Cs1—P1—Cs1xiv | 69.857 (6) |
| O2iii—Cs1—Mg1vi | 71.807 (16) | Cs1ix—P1—Cs1xiv | 105.375 (7) |
| O3iv—Cs1—Mg1vi | 29.64 (2) | Cs1xiii—P1—Cs1xiv | 105.375 (7) |
| O3v—Cs1—Mg1vi | 106.93 (3) | Cs1vi—P1—Cs1xiv | 123.498 (7) |
| O1vi—Cs1—Mg1vi | 29.40 (2) | Cs1ii—P1—Cs1xiv | 123.498 (7) |
| O1ii—Cs1—Mg1vi | 105.34 (2) | P1—O1—Mg1 | 177.02 (12) |
| O1v—Cs1—Mg1vi | 136.22 (2) | P1—O1—Cs1vi | 97.77 (4) |
| O1iv—Cs1—Mg1vi | 68.03 (2) | Mg1—O1—Cs1vi | 84.06 (4) |
| O3vii—Cs1—Mg1vi | 54.563 (11) | P1—O1—Cs1ii | 97.77 (4) |
| O1—Mg1—O3viii | 105.76 (8) | Mg1—O1—Cs1ii | 84.06 (4) |
| O1—Mg1—O2ix | 109.29 (4) | Cs1vi—O1—Cs1ii | 103.38 (4) |
| O3viii—Mg1—O2ix | 113.71 (4) | P1—O1—Cs1ix | 86.93 (5) |
| O1—Mg1—O2x | 109.29 (4) | Mg1—O1—Cs1ix | 91.12 (4) |
| O3viii—Mg1—O2x | 113.71 (4) | Cs1vi—O1—Cs1ix | 174.41 (4) |
| O2ix—Mg1—O2x | 105.04 (6) | Cs1ii—O1—Cs1ix | 78.860 (3) |
| O1—Mg1—Cs1vi | 66.55 (3) | P1—O1—Cs1xiii | 86.93 (5) |
| O3viii—Mg1—Cs1vi | 64.25 (3) | Mg1—O1—Cs1xiii | 91.12 (4) |
| O2ix—Mg1—Cs1vi | 173.66 (3) | Cs1vi—O1—Cs1xiii | 78.860 (3) |
| O2x—Mg1—Cs1vi | 81.10 (3) | Cs1ii—O1—Cs1xiii | 174.41 (4) |
| O1—Mg1—Cs1ii | 66.55 (3) | Cs1ix—O1—Cs1xiii | 98.45 (4) |
| O3viii—Mg1—Cs1ii | 64.25 (3) | P1—O2—Mg1v | 136.32 (7) |
| O2ix—Mg1—Cs1ii | 81.10 (3) | P1—O2—Cs1 | 102.59 (4) |
| O2x—Mg1—Cs1ii | 173.66 (3) | Mg1v—O2—Cs1 | 105.27 (4) |
| Cs1vi—Mg1—Cs1ii | 92.725 (11) | P1—O2—Cs1ii | 110.51 (4) |
| O1—Mg1—Cs1xi | 173.62 (6) | Mg1v—O2—Cs1ii | 98.78 (3) |
| O3viii—Mg1—Cs1xi | 67.86 (6) | Cs1—O2—Cs1ii | 96.94 (3) |
| O2ix—Mg1—Cs1xi | 74.24 (3) | P1—O3—Mg1xii | 178.96 (13) |
| O2x—Mg1—Cs1xi | 74.24 (3) | P1—O3—Cs1ix | 94.51 (5) |
| Cs1vi—Mg1—Cs1xi | 109.444 (9) | Mg1xii—O3—Cs1ix | 86.11 (4) |
| Cs1ii—Mg1—Cs1xi | 109.444 (9) | P1—O3—Cs1xiii | 94.51 (5) |
| O1—Mg1—Cs1xii | 116.54 (5) | Mg1xii—O3—Cs1xiii | 86.11 (4) |
| O3viii—Mg1—Cs1xii | 137.70 (6) | Cs1ix—O3—Cs1xiii | 106.58 (5) |
| O2ix—Mg1—Cs1xii | 52.79 (3) | P1—O3—Cs1xiv | 95.14 (8) |
| O2x—Mg1—Cs1xii | 52.79 (3) | Mg1xii—O3—Cs1xiv | 83.82 (6) |
| Cs1vi—Mg1—Cs1xii | 133.015 (6) | Cs1ix—O3—Cs1xiv | 125.67 (3) |
| Cs1ii—Mg1—Cs1xii | 133.015 (6) | Cs1xiii—O3—Cs1xiv | 125.67 (3) |
| Cs1xi—Mg1—Cs1xii | 69.840 (9) |
| Symmetry codes: (i) x, −y+1/2, z; (ii) −x+1, −y, −z+1; (iii) −x+1, y+1/2, −z+1; (iv) −x+1/2, −y+1, z+1/2; (v) −x+1/2, −y, z+1/2; (vi) −x+1, −y+1, −z+1; (vii) x+1/2, y, −z+3/2; (viii) x+1/2, y, −z+1/2; (ix) −x+1/2, −y, z−1/2; (x) −x+1/2, y+1/2, z−1/2; (xi) x, y, z−1; (xii) x−1/2, y, −z+1/2; (xiii) −x+1/2, −y+1, z−1/2; (xiv) x−1/2, y, −z+3/2. |
| Cs1—O2 | 3.1951 (9) | Mg1—O1 | 1.8847 (13) |
| Cs1—O2i | 3.2166 (9) | Mg1—O3iv | 1.8932 (13) |
| Cs1—O3ii | 3.4476 (11) | Mg1—O2v | 1.9228 (8) |
| Cs1—O1i | 3.5224 (11) | P1—O1 | 1.5056 (13) |
| Cs1—O1ii | 3.6496 (11) | P1—O3 | 1.5138 (13) |
| Cs1—O3iii | 3.6968 (18) | P1—O2 | 1.5249 (8) |
| Symmetry codes: (i) −x+1, −y, −z+1; (ii) −x+1/2, −y+1, z+1/2; (iii) x+1/2, y, −z+3/2; (iv) x+1/2, y, −z+1/2; (v) −x+1/2, −y, z−1/2. |
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Double phosphates AIBIIPO4 (AI = alkali metal; BII = Ca, Sr, Ba, Zn, Cd, Pb) exhibit important properties such as ferroelectric and nonlinear optical behaviour (Blum et al., 1984; Elouadi et al., 1984; Sawada et al., 2003). Among some orthophosphates containing Cs and divalent metals, several polymorphs have been found. For instance, CsZnPO4 occurs in a monoclinic (space group P21/a) and two orthorhombic types (space groups Pna21 and Pnma) (Blum et al., 1986). In contrast, CsMnPO4 occurs in only one type (space group Pna21) (Yakubovich et al., 1990). CsMgPO4, reported here, is isotypic with the Pnma form of CsZnPO4.
Except for O2 (8d), all atoms are in special positions (4c) (Fig. 1). Each MgO4 tetrahedron is linked with four PO4 tetrahedra via common vertices, resulting in a three-dimensional framework with two types of hexagonal channels, filled by Cs atoms, along the a and b directions (Fig. 2). With a cut-off distance of 3.7 Å, the Cs atoms are 11-coordinate. In general, the principles of crystal structure building are equivalent to those in CsMIIPO4 (MII = Mn, Zn) (Yakubovich et al., 1990; Blum et al., 1986) and CsLi0.5Al0.5PO4 (Zapirov et al., 2008).