Acta Cryst. (2009). E65, i76-i77 [ doi:10.1107/S1600536809041105 ]
Single crystals of Ba0.96Eu0.04BrI (barium europium bromide iodide) were grown by the Bridgman technique. The title compound adopts the ordered PbCl2 structure [Braekken (1932). Z. Kristallogr. 83, 222-282]. All atoms occupy the fourfold special positions (4c, site symmetry m) of the space group Pnma with a statistical distribution of Ba and Eu. They lie on the mirror planes, perpendicular to the b axis at y = ±0.25. Each cation is coordinated by nine anions in a tricapped trigonal prismatic arrangement.
Single crystals with the composition Ba0.96Eu0.04BrI were grown by the vertical Bridgman techniques. BaBr2, BaI2, EuBr2 and EuI2 were obtained commerically, mixed in the molar ratio 0.48: 0.48: 0.02: 0.02 and sealed in a quartz ampoule under a dynamic vacuum of 1.10 –6 Torr. The sealed ampoule, about 1 cm in diameter, was heated in a 24 zone Mellen furnace to a temperature of 1123 K and directionally cooled to provide a growth rate of 1 mm/hour. The reactants and products are moisture-sensitive and all manipulations were carried out inside an Argon-filled glove box. The crystal obtained is colorless.
The doping of Eu(ii) on the Ba(ii) site was modeled with a fractional Eu atom fixed in the same location and with the same thermal parameters as the Ba(ii) atom. The relative occupancy factor refined to 0.963 (13) Ba, 0.037 (13) Eu.
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: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).
![[Figure 1]](./fi2082fig1thm.gif)
| Fig. 1. Arrangement of anions around each Ba atom. The displacement ellipsoids are given at 50% probability. The symmetry codes are: (i) -x + 1, -y, -z; (ii) -x + 1, -y + 1, -z; (iii) -x + 3/2, -y + 1, z + 1/2; (iv) -x + 3/2, -y, z + 1/2; (v) x, y + 1, z; (vi) -x + 3/2, -y, z - 1/2; (vii) -x + 2, -y, -z; (viii) -x + 3/2, -y + 1, z - 1/2; (ix) x, y - 1, z. |
| Ba0.96Eu0.04BrI | F(000) = 576.7 |
| Mr = 344.70 | Dx = 5.179 Mg m−3 |
| Orthorhombic, Pnma | Mo Kα radiation, λ = 0.71073 Å |
| Hall symbol: -P 2ac 2n | Cell parameters from 1548 reflections |
| a = 8.684 (3) Å | θ = 4.5–25.4° |
| b = 5.0599 (19) Å | µ = 24.97 mm−1 |
| c = 10.061 (4) Å | T = 153 K |
| V = 442.1 (3) Å3 | Block, colourless |
| Z = 4 | 0.14 × 0.09 × 0.06 mm |
| Bruker SMART 1000 CCD diffractometer | 430 independent reflections |
| Radiation source: fine-focus sealed tube | 370 reflections with I > 2σ(I) |
| graphite | Rint = 0.027 |
| Detector resolution: 8.192 pixels mm-1 | θmax = 25.0°, θmin = 3.1° |
| φ and ω scans | h = −9→10 |
| Absorption correction: multi-scan (Blessing, 1995) | k = −6→5 |
| Tmin = 0.128, Tmax = 0.316 | l = −11→11 |
| 2609 measured reflections |
| Refinement on F2 | Primary atom site location: heavy-atom method |
| Least-squares matrix: full | w = 1/[σ2(Fo2) + (0.02P)2] where P = (Fo2 + 2Fc2)/3 |
| R[F2 > 2σ(F2)] = 0.015 | (Δ/σ)max = 0.001 |
| wR(F2) = 0.033 | Δρmax = 0.89 e Å−3 |
| S = 1.01 | Δρmin = −0.78 e Å−3 |
| 430 reflections | Extinction correction: SHELXL97 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
| 21 parameters | Extinction coefficient: 0.0151 (5) |
| 0 restraints |
| Ba0.96Eu0.04BrI | V = 442.1 (3) Å3 |
| Mr = 344.70 | Z = 4 |
| Orthorhombic, Pnma | Mo Kα radiation |
| a = 8.684 (3) Å | µ = 24.97 mm−1 |
| b = 5.0599 (19) Å | T = 153 K |
| c = 10.061 (4) Å | 0.14 × 0.09 × 0.06 mm |
| Bruker SMART 1000 CCD diffractometer | 430 independent reflections |
| Absorption correction: multi-scan (Blessing, 1995) | 370 reflections with I > 2σ(I) |
| Tmin = 0.128, Tmax = 0.316 | Rint = 0.027 |
| 2609 measured reflections | θmax = 25.0° |
| R[F2 > 2σ(F2)] = 0.015 | Δρmax = 0.89 e Å−3 |
| wR(F2) = 0.033 | Δρmin = −0.78 e Å−3 |
| S = 1.01 | Absolute structure: ? |
| 430 reflections | Flack parameter: ? |
| 21 parameters | Rogers parameter: ? |
| 0 restraints |
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. The doping of Eu(ii) on the Ba(ii) site was modeled with a fractional Eu atom fixed in the same location and with the same thermal parameters as the Ba(ii) atom. The relative occupancy factor refined to 0.963 (13) Ba, 0.037 (13) Eu. |
| x | y | z | Uiso*/Ueq | Occ. (<1) | |
| I1 | 0.52804 (5) | 0.2500 | 0.16976 (4) | 0.01285 (18) | |
| Ba1 | 0.76955 (4) | 0.2500 | −0.12472 (4) | 0.01213 (17) | 0.963 (13) |
| Eu1 | 0.76955 (4) | 0.2500 | −0.12472 (4) | 0.01213 (17) | 0.037 (13) |
| Br1 | 0.85573 (8) | −0.2500 | 0.06634 (6) | 0.0107 (2) |
| U11 | U22 | U33 | U12 | U13 | U23 | |
| I1 | 0.0119 (3) | 0.0139 (3) | 0.0128 (2) | 0.000 | 0.00011 (16) | 0.000 |
| Ba1 | 0.0110 (3) | 0.0126 (3) | 0.0128 (2) | 0.000 | −0.00069 (15) | 0.000 |
| Eu1 | 0.0110 (3) | 0.0126 (3) | 0.0128 (2) | 0.000 | −0.00069 (15) | 0.000 |
| Br1 | 0.0096 (4) | 0.0119 (5) | 0.0105 (3) | 0.000 | −0.0008 (2) | 0.000 |
| I1—Ba1 | 3.6299 (11) | Ba1—Br1vii | 3.3065 (14) |
| I1—Ba1i | 3.6448 (10) | Ba1—I1i | 3.6448 (10) |
| I1—Ba1ii | 3.6448 (10) | Ba1—I1ii | 3.6448 (10) |
| I1—Ba1iii | 3.7101 (9) | Ba1—I1vi | 3.7101 (9) |
| I1—Ba1iv | 3.7101 (9) | Ba1—I1viii | 3.7101 (9) |
| Ba1—Br1v | 3.2643 (10) | Br1—Ba1ix | 3.2643 (10) |
| Ba1—Br1 | 3.2643 (10) | Br1—Ba1iv | 3.2930 (13) |
| Ba1—Br1vi | 3.2931 (13) | Br1—Ba1vii | 3.3065 (14) |
| Ba1—I1—Ba1i | 107.950 (19) | Br1—Ba1—I1ii | 140.69 (2) |
| Ba1—I1—Ba1ii | 107.950 (19) | Br1vi—Ba1—I1ii | 69.416 (14) |
| Ba1i—I1—Ba1ii | 87.92 (3) | Br1vii—Ba1—I1ii | 136.041 (16) |
| Ba1—I1—Ba1iii | 100.44 (2) | I1—Ba1—I1ii | 72.051 (19) |
| Ba1i—I1—Ba1iii | 151.463 (16) | I1i—Ba1—I1ii | 87.92 (3) |
| Ba1ii—I1—Ba1iii | 86.09 (3) | Br1v—Ba1—I1vi | 138.42 (2) |
| Ba1—I1—Ba1iv | 100.44 (2) | Br1—Ba1—I1vi | 72.00 (3) |
| Ba1i—I1—Ba1iv | 86.09 (3) | Br1vi—Ba1—I1vi | 68.31 (2) |
| Ba1ii—I1—Ba1iv | 151.463 (16) | Br1vii—Ba1—I1vi | 68.457 (18) |
| Ba1iii—I1—Ba1iv | 85.99 (3) | I1—Ba1—I1vi | 136.767 (14) |
| Br1v—Ba1—Br1 | 101.62 (3) | I1i—Ba1—I1vi | 78.07 (2) |
| Br1v—Ba1—Br1vi | 129.163 (17) | I1ii—Ba1—I1vi | 137.726 (19) |
| Br1—Ba1—Br1vi | 129.163 (17) | Br1v—Ba1—I1viii | 72.00 (3) |
| Br1v—Ba1—Br1vii | 70.719 (16) | Br1—Ba1—I1viii | 138.42 (2) |
| Br1—Ba1—Br1vii | 70.718 (16) | Br1vi—Ba1—I1viii | 68.31 (2) |
| Br1vi—Ba1—Br1vii | 119.523 (18) | Br1vii—Ba1—I1viii | 68.457 (18) |
| Br1v—Ba1—I1 | 69.62 (2) | I1—Ba1—I1viii | 136.767 (14) |
| Br1—Ba1—I1 | 69.62 (2) | I1i—Ba1—I1viii | 137.726 (19) |
| Br1vi—Ba1—I1 | 125.42 (3) | I1ii—Ba1—I1viii | 78.07 (2) |
| Br1vii—Ba1—I1 | 115.06 (2) | I1vi—Ba1—I1viii | 85.99 (3) |
| Br1v—Ba1—I1i | 140.69 (2) | Ba1—Br1—Ba1ix | 101.62 (3) |
| Br1—Ba1—I1i | 72.41 (2) | Ba1ix—Br1—Ba1iv | 118.69 (2) |
| Br1vi—Ba1—I1i | 69.416 (14) | Ba1—Br1—Ba1vii | 109.282 (16) |
| Br1vii—Ba1—I1i | 136.041 (16) | Ba1ix—Br1—Ba1vii | 109.282 (16) |
| I1—Ba1—I1i | 72.051 (19) | Ba1iv—Br1—Ba1vii | 99.06 (2) |
| Br1v—Ba1—I1ii | 72.41 (2) |
| Symmetry codes: (i) −x+1, −y, −z; (ii) −x+1, −y+1, −z; (iii) −x+3/2, −y+1, z+1/2; (iv) −x+3/2, −y, z+1/2; (v) x, y+1, z; (vi) −x+3/2, −y, z−1/2; (vii) −x+2, −y, −z; (viii) −x+3/2, −y+1, z−1/2; (ix) x, y−1, z. |
| I1—Ba1i | 3.6448 (10) | Ba1—Br1v | 3.2643 (10) |
| I1—Ba1ii | 3.6448 (10) | Ba1—Br1 | 3.2643 (10) |
| I1—Ba1iii | 3.7101 (9) | Ba1—Br1vi | 3.2931 (13) |
| I1—Ba1iv | 3.7101 (9) | Ba1—Br1vii | 3.3065 (14) |
| Symmetry codes: (i) −x+1, −y, −z; (ii) −x+1, −y+1, −z; (iii) −x+3/2, −y+1, z+1/2; (iv) −x+3/2, −y, z+1/2; (v) x, y+1, z; (vi) −x+3/2, −y, z−1/2; (vii) −x+2, −y, −z. |
| Ba1—I1i | 3.6448 (10) | Ba1—I1ii | 3.6448 (10) |
| Ba1—I1vi | 3.7101 (9) | Ba1—I1viii | 3.7101 (9) |
| Ba1—Br1vii | 3.3065 (14) | Ba1—Br1v | 3.2643 (10) |
| Ba1—Br1 | 3.2643 (10) | Ba1—Br1vi | 3.2931 (13) |
| Br1v—Ba1—Br1 | 101.62 (3) | Br1—Ba1—I1ii | 140.69 (2) |
| Br1v—Ba1—Br1vi | 129.163 (17) | Br1vi—Ba1—I1ii | 69.416 (14) |
| Br1—Ba1—Br1vi | 129.163 (17) | Br1vii—Ba1—I1ii | 136.041 (16) |
| Br1v—Ba1—Br1vii | 70.719 (16) | Br1v—Ba1—I1vi | .138.42 (2) |
| Br1—Ba1—Br1vii | 70.718 (16) | Br1—Ba1—I1 | 69.62 (2) |
| Br1vi—Ba1—Br1vii | 119.523 (18) | Br1v—Ba1—I1 | 69.62 (2) |
| I1i—Ba1—I1ii | 87.92 (3) | Br1—Ba1—I1vi | 72.00 (3) |
| I1—Ba1—I1vi | 136.767 (14) | Br1vi—Ba1—I1vi | 68.31 (2) |
| I1i—Ba1—I1vi | 78.07 (2) | Br1vii—Ba1—I1vi | 68.457 (18) |
| I1ii—Ba1—I1vi | 137.726 (19) | Br1vi—Ba1—I1 | 125.42 (3) |
| .I1—Ba1—I1ii | .72.051 (19) | Br1vii—Ba1—I1 | 115.06 (2) |
| Br1—Ba1—I1i | 72.41 (2) | Br1v—Ba1—I1i | 140.69 (2) |
| I1—Ba1—I1i | 72.051 (19) | Br1vi—Ba1—I1i | 69.416 (14) |
| Br1vii—Ba1—I1i | 136.041 (16) | Br1v—Ba1—I1ii | .72.41 (2) |
| Symmetry codes: (i) -x+1, -y, -z; (ii) -x+1, -y+1, -z; (iii) -x+3/2, -y+1, z+1/2; (iv) -x+3/2, -y, z+1/2; (v) x, y+1, z; (vi) -x+3/2, -y, z-1/2; (vii) -x+2, -y, -z; (viii) -x+3/2, -y+1, z-1/2; (ix) x, y-1, z. |
This work was supported by the US Department of Homeland Security and carried out at the Lawrence Berkeley National Laboratory under Department of Energy Contract No. DE-AC02-05CH11231. The authors gratefully acknowledge useful discussions with Dr Stephen E. Derenzo and Dr Gregory Bizarri.
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Barium mixed halides activated by Eu2+ have been extensively studied as X-ray phosphors (Schweizer, 2001; Crawford & Brixner, 1991) and scintillators for the detection of γ-rays (Selling et al., 2007). The F-based compounds of the form BaFX (X= Cl, Br, I) have a tetragonal, matlockite structure similar to PbFCl (Liebich & Nicollin, 1977). Among the other barium mixed halides, the structure of BaBrCl has been found to be the PbCl2-type (Hodorowicz et al., 1983). Lenus et al. recently solved the structures of BaBrI and BaClI from X-ray powder diffraction data in the space groups P2221 and Pbam respectively (Lenus et al., 2002). We have synthesized single crystals of Ba0.96Eu0.04BrI and present details of the structure. Eu is introduced as a dopant and substitute for Ba. The doping was not expected to change the structure of the parent material BaBrI. However, we determine the structure to have a space group Pnma, similar to that of isomorphous compounds EuBrI (Liao et al., 2004) and SrBrI (Hodorowicz & Eick, 1983), but not the structure published by Lenus et al. for powders of BaBrI (Lenus et al., 2002)
The title compound adopts the orthorhombic PbCl2 structure. All atoms occupy the fourfold special positions (4c) of the space group D162h-Pnma. They lie on the mirror planes, perpendicular to the b axis at y = (±)0.25. Each Ba/Eu cation is coordinated by 9 anions in a tricapped trigonal prismatic arrangement (Fig. 1). The anions are not equidistant from the Ba cation but present in two different positions. The smaller bromide anions occupy one of the anionic positions at distances between 3.26 and 3.30 Å. The larger iodide anions occupy the second anionic position (distances 3.62 - 3.71 Å), giving a completely ordered structure for the anions. The same ordering has been observed in isomorphous compounds EuBrI (Liao et al., 2004) and SrBrI (Hodorowicz & Eick, 1983).
The Eu content of 4% has been determined from the refinement of the structure. The presence of divalent Eu is also confirmed by measuring the emission curve under X-ray excitation. The characteristic 4f65 d1 → 4f7transition of Eu2+ was observed. A detailed study of the luminescent properties is currently underway and will be presented in a future publication (Bourret-Courchesne et al., 2009).