Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270112043016/fn3113sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270112043016/fn3113H339sup2.hkl | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270112043016/fn3113H347sup3.hkl |
For related literature, see: Brown & Altermatt (1985); Dal (2011); Fransolet (1975); Gorbunov et al. (1980); Hughes et al. (1988); Lightfoot & Cheetham (1986); Redhammer et al. (2004); Tuttle (1949); Vencato et al. (1994).
Both single crystals used for the structure refinement were synthesized under hydrothermal conditions. The starting materials were prepared by mixing Li3PO4, FePO4 and Fe in molar proportions 1:5:1 (H.339) and 1:11.5:1 (H.347), and then by homogenizing this mixture in an agate mortar. About 25 mg of each mixture were sealed into gold tubes with outer diameters of 2 mm and lengths of 25 mm, containing 2 mg of pure water. The gold capsules were then inserted in a Tuttle-type pressure vessel (Tuttle, 1949) and maintained at a temperature of 973 K and a pressure of 0.1 GPa. After 7 d, the gold tubes containing the samples were quenched in the autoclave to room temperature in a stream of cold air. Black crystals of H.339 are found in association with colourless crystals of LiFePO4 and green crystals of Li3Fe2(PO4)3. Black crystals of H.347 crystallized in association with light green crystals of LiFe(P2O7) and Li3Fe2(PO4)3.
A chemical analysis has been performed with a CAMEBAX SX-100 electron microprobe (15 kV acceleration voltage, 5 nA beam current, analyst T. Theye cite in acknowledgements?, Stuttgart, Germany). The standard used to calibrate both Fe and P was graftonite from Kabira (sample KF16, Fransolet, 1975). The average of ten point analyses for H.339 gives P2O5 44.90, FeO* 20.00, Fe2O3* 33.68, H2O* 0.68, total 99.27 wt%. The chemical composition, calculated on the basis of six P atoms and four FeIII atoms per formula unit, corresponds to FeII2.64FeIII4(PO4)5.28(HPO4)0.72. For H.347, the average of 12 point analyses gives P2O5 46.57, FeO* 15.11, Fe2O3* 34.93, H2O* 1.80, total 99.68 wt% [* indicates values calculated to maintain charge balance, assuming the substitution mechanism FeII + 2(PO4)3- = vacancies + 2(HPO4)2-]. The chemical compositon, calculated on the basis of six P atoms and four FeIII atoms per formula unit, corresponds to FeII2.08FeIII4(PO4)4.16(HPO4)1.84. Both formulas are in fairly good agreement with the compositions calculated from the structural data, which are FeII2.67FeIII4(PO4)5.35(HPO4)0.65 (H.339) and FeII2.23FeIII4(PO4)4.45(HPO4)1.55 (H.347).
All atoms were refined anisotropically in both structures. The refined site-occupancy factors then indicated low electronic densities on the Fe4 site, thus showing that this site was not fully occupied by FeII. Therefore, FeII and vacancies were refined on the Fe4 site. The low amounts of HPO42- groups occurring in sample H.339 prevented any determination of H-atom positions; however, one H-atom position was located in sample H.347 by difference Fourier map.
For both compounds, data collection: CrysAlis PRO (Agilent, 2012); cell refinement: CrysAlis PRO (Agilent, 2012); data reduction: CrysAlis PRO (Agilent, 2012); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ATOMS (Dowty, 1993); software used to prepare material for publication: OLEX2 (Dolomanov et al., 2009).
Fe6.67(PO4)5.35(HPO4)0.65 | Z = 1 |
Mr = 942.93 | F(000) = 456.07 |
Triclinic, P1 | Dx = 3.804 Mg m−3 |
a = 6.3609 (10) Å | Mo Kα radiation, λ = 0.7107 Å |
b = 7.9750 (13) Å | Cell parameters from 7440 reflections |
c = 9.3220 (15) Å | θ = 2.5–30.4° |
α = 105.278 (14)° | µ = 6.44 mm−1 |
β = 108.055 (14)° | T = 293 K |
γ = 101.993 (14)° | Isometric crystal, black |
V = 411.55 (12) Å3 | 0.10 × 0.08 × 0.07 mm |
Agilent Xcalibur Eos diffractometer | 2404 independent reflections |
Radiation source: Enhance (Mo) X-ray Source | 2084 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.039 |
Detector resolution: 16.0087 pixels mm-1 | θmax = 30.5°, θmin = 2.5° |
ω scans | h = −9→8 |
Absorption correction: multi-scan (CrysAlis PRO; Agilent, 2012) | k = −11→11 |
Tmin = 0.543, Tmax = 0.640 | l = −13→13 |
21890 measured reflections |
Refinement on F2 | 0 restraints |
Least-squares matrix: full | Primary atom site location: structure-invariant direct methods |
R[F2 > 2σ(F2)] = 0.024 | Secondary atom site location: difference Fourier map |
wR(F2) = 0.057 | w = 1/[σ2(Fo2) + (0.0224P)2 + 0.4764P] where P = (Fo2 + 2Fc2)/3 |
S = 1.10 | (Δ/σ)max < 0.001 |
2404 reflections | Δρmax = 0.62 e Å−3 |
170 parameters | Δρmin = −0.50 e Å−3 |
Fe6.67(PO4)5.35(HPO4)0.65 | γ = 101.993 (14)° |
Mr = 942.93 | V = 411.55 (12) Å3 |
Triclinic, P1 | Z = 1 |
a = 6.3609 (10) Å | Mo Kα radiation |
b = 7.9750 (13) Å | µ = 6.44 mm−1 |
c = 9.3220 (15) Å | T = 293 K |
α = 105.278 (14)° | 0.10 × 0.08 × 0.07 mm |
β = 108.055 (14)° |
Agilent Xcalibur Eos diffractometer | 2404 independent reflections |
Absorption correction: multi-scan (CrysAlis PRO; Agilent, 2012) | 2084 reflections with I > 2σ(I) |
Tmin = 0.543, Tmax = 0.640 | Rint = 0.039 |
21890 measured reflections |
R[F2 > 2σ(F2)] = 0.024 | 170 parameters |
wR(F2) = 0.057 | 0 restraints |
S = 1.10 | Δρmax = 0.62 e Å−3 |
2404 reflections | Δρmin = −0.50 e Å−3 |
Experimental. Absorption correction: CrysAlisPro, Agilent Technologies, Version 1.171.35.21 (release 20-01-2012 CrysAlis171 .NET) (compiled Jan 23 2012,18:06:46) Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm. |
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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 > 2sigma(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 | Occ. (<1) | |
Fe1 | 0.11782 (6) | 0.04568 (5) | 0.38554 (4) | 0.01338 (8) | |
Fe2 | 0.45486 (6) | −0.22200 (5) | −0.02741 (4) | 0.01292 (9) | |
Fe3 | 0.5000 | 0.5000 | 0.5000 | 0.01590 (11) | |
Fe4 | 0.21811 (7) | −0.31143 (6) | 0.21270 (5) | 0.01511 (14) | 0.8369 (18) |
P1 | 0.40324 (10) | −0.09557 (8) | 0.66575 (7) | 0.01167 (12) | |
P2 | −0.27138 (10) | −0.34924 (8) | 0.26723 (7) | 0.01186 (12) | |
P3 | −0.09965 (11) | −0.26775 (9) | −0.12952 (7) | 0.01258 (12) | |
O1 | 0.1896 (3) | −0.0383 (2) | 0.5847 (2) | 0.0139 (3) | |
O2 | −0.0426 (3) | −0.2318 (2) | 0.2725 (2) | 0.0141 (3) | |
O3 | 0.5193 (3) | −0.3106 (2) | 0.1581 (2) | 0.0146 (3) | |
O4 | 0.1344 (3) | −0.2605 (2) | −0.0070 (2) | 0.0156 (3) | |
O5 | 0.3790 (3) | −0.0296 (2) | 0.3387 (2) | 0.0152 (3) | |
O6 | 0.4322 (3) | −0.0519 (2) | −0.1545 (2) | 0.0137 (3) | |
O7 | −0.2224 (3) | −0.4589 (2) | −0.2611 (2) | 0.0183 (4) | |
O8 | 0.3704 (3) | −0.2918 (2) | 0.5788 (2) | 0.0196 (4) | |
O9 | 0.7502 (3) | −0.2188 (3) | −0.0368 (2) | 0.0192 (4) | |
O10 | −0.2888 (3) | −0.5483 (2) | 0.2046 (2) | 0.0172 (4) | |
O11 | 0.0503 (3) | 0.1327 (3) | 0.2131 (2) | 0.0191 (4) | |
O12 | 0.2714 (3) | 0.3008 (2) | 0.5591 (2) | 0.0150 (3) |
U11 | U22 | U33 | U12 | U13 | U23 | |
Fe1 | 0.01316 (17) | 0.01413 (17) | 0.01370 (17) | 0.00410 (13) | 0.00582 (13) | 0.00559 (13) |
Fe2 | 0.01292 (16) | 0.01290 (17) | 0.01293 (17) | 0.00412 (13) | 0.00486 (13) | 0.00465 (13) |
Fe3 | 0.0193 (3) | 0.0140 (2) | 0.0158 (2) | 0.00621 (19) | 0.0078 (2) | 0.0052 (2) |
Fe4 | 0.0158 (2) | 0.0144 (2) | 0.0175 (2) | 0.00576 (16) | 0.00831 (17) | 0.00637 (17) |
P1 | 0.0118 (3) | 0.0121 (3) | 0.0117 (3) | 0.0040 (2) | 0.0051 (2) | 0.0043 (2) |
P2 | 0.0113 (3) | 0.0122 (3) | 0.0120 (3) | 0.0034 (2) | 0.0047 (2) | 0.0041 (2) |
P3 | 0.0115 (3) | 0.0135 (3) | 0.0127 (3) | 0.0041 (2) | 0.0046 (2) | 0.0046 (2) |
O1 | 0.0130 (8) | 0.0161 (8) | 0.0137 (8) | 0.0053 (7) | 0.0055 (6) | 0.0057 (7) |
O2 | 0.0125 (8) | 0.0146 (8) | 0.0152 (8) | 0.0030 (6) | 0.0065 (7) | 0.0049 (7) |
O3 | 0.0124 (8) | 0.0165 (8) | 0.0143 (8) | 0.0041 (7) | 0.0043 (6) | 0.0059 (7) |
O4 | 0.0138 (8) | 0.0202 (9) | 0.0140 (8) | 0.0072 (7) | 0.0054 (7) | 0.0064 (7) |
O5 | 0.0136 (8) | 0.0172 (9) | 0.0151 (8) | 0.0035 (7) | 0.0068 (7) | 0.0056 (7) |
O6 | 0.0150 (8) | 0.0152 (8) | 0.0125 (8) | 0.0052 (7) | 0.0060 (6) | 0.0059 (7) |
O7 | 0.0191 (9) | 0.0148 (9) | 0.0164 (9) | 0.0048 (7) | 0.0031 (7) | 0.0031 (7) |
O8 | 0.0258 (10) | 0.0152 (9) | 0.0197 (9) | 0.0095 (8) | 0.0100 (8) | 0.0052 (7) |
O9 | 0.0156 (8) | 0.0281 (10) | 0.0175 (9) | 0.0098 (7) | 0.0086 (7) | 0.0084 (8) |
O10 | 0.0181 (9) | 0.0144 (8) | 0.0176 (9) | 0.0047 (7) | 0.0066 (7) | 0.0040 (7) |
O11 | 0.0186 (9) | 0.0194 (9) | 0.0210 (9) | 0.0045 (7) | 0.0070 (7) | 0.0115 (8) |
O12 | 0.0157 (8) | 0.0151 (8) | 0.0124 (8) | 0.0020 (7) | 0.0058 (7) | 0.0040 (7) |
Fe1—O1 | 2.0877 (17) | Fe4—O2 | 2.0712 (18) |
Fe1—O1i | 2.0501 (17) | Fe4—O3 | 2.1284 (18) |
Fe1—O2 | 2.0529 (18) | Fe4—O4 | 2.1198 (18) |
Fe1—O5 | 2.0092 (18) | Fe4—O5 | 2.0941 (19) |
Fe1—O11 | 1.8802 (18) | Fe4—O7iii | 2.0017 (19) |
Fe1—O12 | 2.0423 (18) | P1—O1 | 1.5588 (18) |
Fe2—O3 | 1.9955 (18) | P1—O6ix | 1.5611 (18) |
Fe2—O4 | 2.0727 (18) | P1—O5vii | 1.5493 (18) |
Fe2—O6 | 2.0215 (17) | P1—O8 | 1.4963 (19) |
Fe2—O6ii | 2.1921 (18) | P2—O2 | 1.5368 (18) |
Fe2—O9 | 1.9028 (18) | P2—O3x | 1.5490 (18) |
Fe2—O10iii | 1.9290 (19) | P2—O12i | 1.5627 (18) |
Fe3—O12 | 2.2222 (17) | P2—O10 | 1.5070 (19) |
Fe3—O12iv | 2.2222 (17) | P3—O4 | 1.5495 (18) |
Fe3—O7v | 2.2635 (18) | P3—O9x | 1.5170 (19) |
Fe3—O7vi | 2.2635 (18) | P3—O11v | 1.5225 (19) |
Fe3—O8vii | 2.0688 (18) | P3—O7 | 1.5377 (19) |
Fe3—O8viii | 2.0688 (18) | ||
O1i—Fe1—O1 | 82.49 (7) | O8viii—Fe3—O12 | 93.32 (7) |
O1i—Fe1—O2 | 82.94 (7) | O8vii—Fe3—O12 | 86.68 (7) |
O2—Fe1—O1 | 79.79 (7) | O8viii—Fe3—O12iv | 86.68 (7) |
O5—Fe1—O1 | 90.53 (7) | O8viii—Fe3—O7v | 81.40 (7) |
O5—Fe1—O1i | 162.52 (7) | O8vii—Fe3—O7v | 98.60 (7) |
O5—Fe1—O2 | 80.05 (7) | O8viii—Fe3—O7vi | 98.60 (7) |
O5—Fe1—O12 | 105.50 (7) | O8vii—Fe3—O7vi | 81.40 (7) |
O11—Fe1—O1 | 176.80 (8) | O8vii—Fe3—O8viii | 179.999 (1) |
O11—Fe1—O1i | 95.73 (8) | O2—Fe4—O3 | 163.02 (7) |
O11—Fe1—O2 | 102.68 (8) | O2—Fe4—O4 | 96.12 (7) |
O11—Fe1—O5 | 91.90 (8) | O2—Fe4—O5 | 77.69 (7) |
O11—Fe1—O12 | 94.46 (8) | O4—Fe4—O3 | 76.48 (7) |
O12—Fe1—O1 | 82.88 (7) | O5—Fe4—O3 | 86.85 (7) |
O12—Fe1—O1i | 89.59 (7) | O5—Fe4—O4 | 89.29 (7) |
O12—Fe1—O2 | 161.87 (7) | O7iii—Fe4—O2 | 106.40 (7) |
O3—Fe2—O4 | 80.51 (7) | O7iii—Fe4—O3 | 89.61 (7) |
O3—Fe2—O6ii | 85.77 (7) | O7iii—Fe4—O4 | 131.85 (7) |
O3—Fe2—O6 | 160.98 (7) | O7iii—Fe4—O5 | 136.39 (7) |
O4—Fe2—O6ii | 87.28 (7) | O1—P1—O6ix | 105.76 (10) |
O6—Fe2—O4 | 99.45 (7) | O5vii—P1—O1 | 107.68 (10) |
O6—Fe2—O6ii | 75.25 (7) | O5vii—P1—O6ix | 108.29 (10) |
O9—Fe2—O3 | 92.25 (8) | O8—P1—O1 | 111.23 (11) |
O9—Fe2—O4 | 171.18 (8) | O8—P1—O6ix | 113.87 (10) |
O9—Fe2—O6ii | 97.27 (8) | O8—P1—O5vii | 109.75 (11) |
O9—Fe2—O6 | 89.04 (8) | O2—P2—O3x | 109.81 (10) |
O9—Fe2—O10iii | 94.14 (8) | O2—P2—O12i | 109.72 (10) |
O10iii—Fe2—O3 | 100.35 (8) | O3x—P2—O12i | 108.83 (10) |
O10iii—Fe2—O4 | 82.31 (8) | O10—P2—O2 | 108.78 (10) |
O10iii—Fe2—O6 | 98.48 (8) | O10—P2—O3x | 110.94 (10) |
O10iii—Fe2—O6ii | 166.84 (7) | O10—P2—O12i | 108.74 (10) |
O12—Fe3—O12iv | 180.0 | O9x—P3—O4 | 107.65 (10) |
O12—Fe3—O7v | 94.64 (7) | O9x—P3—O11v | 111.43 (11) |
O12iv—Fe3—O7v | 85.36 (7) | O9x—P3—O7 | 110.85 (11) |
O12iv—Fe3—O7vi | 94.64 (7) | O11v—P3—O4 | 108.84 (11) |
O12—Fe3—O7vi | 85.36 (7) | O11v—P3—O7 | 107.18 (11) |
O7v—Fe3—O7vi | 180.00 (9) | O7—P3—O4 | 110.91 (10) |
O8vii—Fe3—O12iv | 93.32 (7) |
Symmetry codes: (i) −x, −y, −z+1; (ii) −x+1, −y, −z; (iii) −x, −y−1, −z; (iv) −x+1, −y+1, −z+1; (v) −x, −y, −z; (vi) x+1, y+1, z+1; (vii) −x+1, −y, −z+1; (viii) x, y+1, z; (ix) x, y, z+1; (x) x−1, y, z. |
Fe6.23(PO4)4.45(HPO4)1.55 | Z = 1 |
Mr = 919.26 | F(000) = 445.53 |
Triclinic, P1 | Dx = 3.750 Mg m−3 |
a = 6.3445 (2) Å | Mo Kα radiation, λ = 0.7107 Å |
b = 7.9353 (3) Å | Cell parameters from 11179 reflections |
c = 9.2829 (3) Å | θ = 2.5–30.4° |
α = 105.303 (3)° | µ = 6.13 mm−1 |
β = 108.176 (3)° | T = 293 K |
γ = 101.700 (3)° | Isometric crystal, black |
V = 407.03 (2) Å3 | 0.15 × 0.10 × 0.06 mm |
Agilent Xcalibur Eos diffractometer | 2378 independent reflections |
Radiation source: Enhance (Mo) X-ray Source | 2167 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.031 |
Detector resolution: 16.0087 pixels mm-1 | θmax = 30.5°, θmin = 2.5° |
ω scans | h = −9→9 |
Absorption correction: analytical [CrysAlis PRO (Agilent, 2012), based on expressions derived by Clark & Reid (1995)] | k = −11→11 |
Tmin = 0.573, Tmax = 0.786 | l = −13→13 |
21571 measured reflections |
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)] = 0.027 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.085 | w = 1/[σ2(Fo2) + (0.0503P)2 + 0.6294P] where P = (Fo2 + 2Fc2)/3 |
S = 1.14 | (Δ/σ)max < 0.001 |
2378 reflections | Δρmax = 0.96 e Å−3 |
170 parameters | Δρmin = −0.68 e Å−3 |
0 restraints |
Fe6.23(PO4)4.45(HPO4)1.55 | γ = 101.700 (3)° |
Mr = 919.26 | V = 407.03 (2) Å3 |
Triclinic, P1 | Z = 1 |
a = 6.3445 (2) Å | Mo Kα radiation |
b = 7.9353 (3) Å | µ = 6.13 mm−1 |
c = 9.2829 (3) Å | T = 293 K |
α = 105.303 (3)° | 0.15 × 0.10 × 0.06 mm |
β = 108.176 (3)° |
Agilent Xcalibur Eos diffractometer | 2378 independent reflections |
Absorption correction: analytical [CrysAlis PRO (Agilent, 2012), based on expressions derived by Clark & Reid (1995)] | 2167 reflections with I > 2σ(I) |
Tmin = 0.573, Tmax = 0.786 | Rint = 0.031 |
21571 measured reflections |
R[F2 > 2σ(F2)] = 0.027 | 170 parameters |
wR(F2) = 0.085 | 0 restraints |
S = 1.14 | Δρmax = 0.96 e Å−3 |
2378 reflections | Δρmin = −0.68 e Å−3 |
Experimental. Absorption correction: CrysAlisPro, Agilent Technologies, Version 1.171.35.21 (release 20-01-2012 CrysAlis171 .NET) (compiled Jan 23 2012,18:06:46) Analytical numeric absorption correction using a multifaceted crystal model based on expressions derived by R.C. Clark & J.S. Reid. (Clark, R. C. & Reid, J. S. (1995). Acta Cryst. A51, 887-897) |
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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 > 2sigma(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 | Occ. (<1) | |
Fe1 | −0.61697 (6) | 0.45850 (5) | 0.11678 (4) | 0.00709 (11) | |
Fe2 | −0.04932 (6) | 0.27698 (5) | 0.47371 (5) | 0.00698 (11) | |
Fe3 | 1.0000 | 1.0000 | 0.0000 | 0.00897 (13) | |
Fe4 | 0.28654 (11) | 0.81443 (9) | 0.28898 (8) | 0.0096 (2) | 0.614 (2) |
P1 | −0.09424 (11) | 0.40554 (9) | 0.16637 (8) | 0.00517 (14) | |
P2 | 0.77367 (11) | 0.84989 (9) | 0.23196 (8) | 0.00504 (13) | |
P3 | −0.60279 (11) | 0.23246 (9) | 0.36786 (8) | 0.00614 (14) | |
O1 | −0.3109 (3) | 0.4594 (3) | 0.0836 (2) | 0.0071 (4) | |
O2 | 0.1212 (3) | 0.5322 (3) | 0.1611 (2) | 0.0084 (4) | |
O3 | 0.5450 (3) | 0.7327 (3) | 0.2271 (2) | 0.0081 (3) | |
O4 | −0.0673 (3) | 0.4494 (3) | 0.3459 (2) | 0.0072 (3) | |
O5 | 0.7909 (3) | 1.0499 (3) | 0.2929 (2) | 0.0104 (4) | |
O6 | 0.9837 (3) | 0.8120 (3) | 0.3417 (2) | 0.0085 (4) | |
O7 | 0.7306 (4) | 0.9574 (3) | −0.2321 (3) | 0.0145 (4) | |
O8 | −0.5490 (4) | 0.3726 (3) | 0.2886 (2) | 0.0123 (4) | |
O9 | −0.3711 (3) | 0.2344 (3) | 0.4892 (2) | 0.0103 (4) | |
O10 | 0.2474 (3) | 0.2797 (3) | 0.4626 (2) | 0.0118 (4) | |
O11 | 0.7749 (3) | 0.8007 (3) | 0.0575 (2) | 0.0081 (4) | |
O12 | 0.8785 (4) | 1.2081 (3) | 0.0811 (3) | 0.0139 (4) |
U11 | U22 | U33 | U12 | U13 | U23 | |
Fe1 | 0.00555 (19) | 0.0090 (2) | 0.00715 (19) | 0.00150 (14) | 0.00292 (14) | 0.00362 (15) |
Fe2 | 0.00734 (18) | 0.00644 (18) | 0.00721 (19) | 0.00230 (13) | 0.00257 (14) | 0.00266 (14) |
Fe3 | 0.0105 (3) | 0.0075 (2) | 0.0098 (3) | 0.00357 (19) | 0.0047 (2) | 0.0030 (2) |
Fe4 | 0.0102 (3) | 0.0091 (3) | 0.0130 (4) | 0.0046 (2) | 0.0070 (2) | 0.0048 (3) |
P1 | 0.0052 (3) | 0.0058 (3) | 0.0052 (3) | 0.0020 (2) | 0.0025 (2) | 0.0020 (2) |
P2 | 0.0042 (3) | 0.0054 (3) | 0.0054 (3) | 0.0013 (2) | 0.0022 (2) | 0.0015 (2) |
P3 | 0.0053 (3) | 0.0072 (3) | 0.0072 (3) | 0.0024 (2) | 0.0030 (2) | 0.0035 (2) |
O1 | 0.0032 (8) | 0.0112 (9) | 0.0074 (8) | 0.0023 (7) | 0.0020 (6) | 0.0042 (7) |
O2 | 0.0071 (8) | 0.0108 (9) | 0.0090 (9) | 0.0027 (7) | 0.0048 (7) | 0.0041 (7) |
O3 | 0.0058 (8) | 0.0092 (9) | 0.0090 (8) | 0.0010 (7) | 0.0040 (7) | 0.0023 (7) |
O4 | 0.0091 (8) | 0.0078 (8) | 0.0058 (8) | 0.0032 (7) | 0.0034 (7) | 0.0032 (7) |
O5 | 0.0113 (9) | 0.0075 (9) | 0.0114 (9) | 0.0033 (7) | 0.0038 (7) | 0.0021 (7) |
O6 | 0.0055 (8) | 0.0118 (9) | 0.0089 (8) | 0.0035 (7) | 0.0023 (7) | 0.0047 (7) |
O7 | 0.0154 (10) | 0.0076 (9) | 0.0160 (10) | 0.0009 (7) | 0.0059 (8) | −0.0007 (8) |
O8 | 0.0124 (9) | 0.0135 (9) | 0.0111 (9) | 0.0018 (7) | 0.0027 (7) | 0.0086 (8) |
O9 | 0.0062 (8) | 0.0179 (10) | 0.0110 (9) | 0.0074 (7) | 0.0038 (7) | 0.0082 (8) |
O10 | 0.0080 (9) | 0.0203 (10) | 0.0103 (9) | 0.0075 (8) | 0.0061 (7) | 0.0048 (8) |
O11 | 0.0092 (8) | 0.0085 (9) | 0.0057 (8) | 0.0014 (7) | 0.0038 (7) | 0.0013 (7) |
O12 | 0.0219 (10) | 0.0086 (9) | 0.0135 (10) | 0.0065 (8) | 0.0097 (8) | 0.0028 (8) |
Fe1—O1i | 2.0792 (19) | Fe4—O3 | 2.064 (2) |
Fe1—O1 | 2.0576 (18) | Fe4—O6ii | 2.123 (2) |
Fe1—O3ii | 2.025 (2) | Fe4—O2 | 2.096 (2) |
Fe1—O2ii | 1.9910 (19) | Fe4—O9iv | 2.120 (2) |
Fe1—O11iii | 2.0614 (19) | Fe4—O7viii | 2.029 (2) |
Fe1—O8 | 1.8597 (19) | P2—O3 | 1.537 (2) |
Fe2—O4 | 2.0314 (18) | P2—O5 | 1.506 (2) |
Fe2—O4iv | 2.1731 (19) | P2—O6 | 1.5427 (19) |
Fe2—O5v | 1.922 (2) | P2—O11 | 1.5652 (19) |
Fe2—O6vi | 1.9805 (19) | P1—O1 | 1.5542 (19) |
Fe2—O9 | 2.0573 (19) | P1—O4 | 1.5559 (19) |
Fe2—O10 | 1.914 (2) | P1—O2 | 1.5462 (19) |
Fe3—O11vii | 2.1979 (19) | P1—O12v | 1.504 (2) |
Fe3—O11 | 2.1979 (19) | P3—O9 | 1.542 (2) |
Fe3—O12 | 2.027 (2) | P3—O10ii | 1.519 (2) |
Fe3—O12vii | 2.027 (2) | P3—O8 | 1.526 (2) |
Fe3—O7vii | 2.182 (2) | P3—O7iii | 1.543 (2) |
Fe3—O7 | 2.182 (2) | ||
O1—Fe1—O1i | 82.31 (8) | O12—Fe3—O7vii | 97.10 (8) |
O1—Fe1—O11iii | 89.06 (8) | O12—Fe3—O7 | 82.90 (8) |
O3ii—Fe1—O1i | 79.82 (8) | O12vii—Fe3—O7vii | 82.90 (8) |
O3ii—Fe1—O1 | 83.24 (8) | O7vii—Fe3—O11 | 85.84 (7) |
O3ii—Fe1—O11iii | 161.92 (8) | O7—Fe3—O11 | 94.16 (7) |
O2ii—Fe1—O1 | 164.01 (8) | O7—Fe3—O11vii | 85.84 (7) |
O2ii—Fe1—O1i | 90.55 (8) | O7vii—Fe3—O11vii | 94.16 (7) |
O2ii—Fe1—O3ii | 81.42 (8) | O7vii—Fe3—O7 | 180.0 |
O2ii—Fe1—O11iii | 104.31 (8) | O3—Fe4—O6ii | 162.47 (8) |
O11iii—Fe1—O1i | 82.96 (8) | O3—Fe4—O2 | 78.04 (8) |
O8—Fe1—O1i | 176.45 (9) | O3—Fe4—O9iv | 96.77 (8) |
O8—Fe1—O1 | 95.60 (8) | O2—Fe4—O6ii | 85.71 (8) |
O8—Fe1—O3ii | 102.83 (8) | O2—Fe4—O9iv | 90.12 (8) |
O8—Fe1—O2ii | 92.18 (9) | O9iv—Fe4—O6ii | 76.56 (7) |
O8—Fe1—O11iii | 94.16 (9) | O7viii—Fe4—O3 | 107.08 (9) |
O4—Fe2—O4iv | 74.85 (8) | O7viii—Fe4—O6ii | 88.87 (8) |
O4—Fe2—O9 | 100.32 (8) | O7viii—Fe4—O2 | 133.66 (9) |
O5v—Fe2—O4iv | 167.77 (8) | O7viii—Fe4—O9iv | 132.99 (9) |
O5v—Fe2—O4 | 97.53 (8) | O3—P2—O6 | 110.00 (11) |
O5v—Fe2—O6vi | 101.47 (8) | O3—P2—O11 | 110.02 (11) |
O5v—Fe2—O9 | 82.49 (9) | O5—P2—O3 | 109.10 (11) |
O6vi—Fe2—O4iv | 86.23 (8) | O5—P2—O6 | 110.91 (11) |
O6vi—Fe2—O4 | 160.96 (8) | O5—P2—O11 | 108.23 (11) |
O6vi—Fe2—O9 | 81.21 (8) | O6—P2—O11 | 108.56 (11) |
O9—Fe2—O4iv | 89.40 (8) | O1—P1—O4 | 105.52 (11) |
O10—Fe2—O4iv | 96.57 (8) | O2—P1—O1 | 107.80 (11) |
O10—Fe2—O4 | 87.76 (8) | O2—P1—O4 | 108.80 (11) |
O10—Fe2—O5v | 92.61 (9) | O12v—P1—O1 | 111.44 (12) |
O10—Fe2—O6vi | 92.45 (8) | O12v—P1—O4 | 113.52 (11) |
O10—Fe2—O9 | 171.01 (9) | O12v—P1—O2 | 109.54 (12) |
O11vii—Fe3—O11 | 180.0 | O9—P3—O7iii | 111.39 (12) |
O12vii—Fe3—O11vii | 94.28 (8) | O10ii—P3—O9 | 107.21 (11) |
O12—Fe3—O11vii | 85.72 (8) | O10ii—P3—O8 | 111.87 (12) |
O12vii—Fe3—O11 | 85.72 (8) | O10ii—P3—O7iii | 110.15 (12) |
O12—Fe3—O11 | 94.28 (8) | O8—P3—O9 | 108.64 (11) |
O12vii—Fe3—O12 | 180.00 (10) | O8—P3—O7iii | 107.60 (12) |
O12vii—Fe3—O7 | 97.10 (8) |
Symmetry codes: (i) −x−1, −y+1, −z; (ii) x−1, y, z; (iii) −x, −y+1, −z; (iv) −x, −y+1, −z+1; (v) x−1, y−1, z; (vi) −x+1, −y+1, −z+1; (vii) −x+2, −y+2, −z; (viii) −x+1, −y+2, −z. |
Experimental details
(H339) | (H347) | |
Crystal data | ||
Chemical formula | Fe6.67(PO4)5.35(HPO4)0.65 | Fe6.23(PO4)4.45(HPO4)1.55 |
Mr | 942.93 | 919.26 |
Crystal system, space group | Triclinic, P1 | Triclinic, P1 |
Temperature (K) | 293 | 293 |
a, b, c (Å) | 6.3609 (10), 7.9750 (13), 9.3220 (15) | 6.3445 (2), 7.9353 (3), 9.2829 (3) |
α, β, γ (°) | 105.278 (14), 108.055 (14), 101.993 (14) | 105.303 (3), 108.176 (3), 101.700 (3) |
V (Å3) | 411.55 (12) | 407.03 (2) |
Z | 1 | 1 |
Radiation type | Mo Kα | Mo Kα |
µ (mm−1) | 6.44 | 6.13 |
Crystal size (mm) | 0.10 × 0.08 × 0.07 | 0.15 × 0.10 × 0.06 |
Data collection | ||
Diffractometer | Agilent Xcalibur Eos diffractometer | Agilent Xcalibur Eos diffractometer |
Absorption correction | Multi-scan (CrysAlis PRO; Agilent, 2012) | Analytical [CrysAlis PRO (Agilent, 2012), based on expressions derived by Clark & Reid (1995)] |
Tmin, Tmax | 0.543, 0.640 | 0.573, 0.786 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 21890, 2404, 2084 | 21571, 2378, 2167 |
Rint | 0.039 | 0.031 |
(sin θ/λ)max (Å−1) | 0.714 | 0.714 |
Refinement | ||
R[F2 > 2σ(F2)], wR(F2), S | 0.024, 0.057, 1.10 | 0.027, 0.085, 1.14 |
No. of reflections | 2404 | 2378 |
No. of parameters | 170 | 170 |
Δρmax, Δρmin (e Å−3) | 0.62, −0.50 | 0.96, −0.68 |
Computer programs: CrysAlis PRO (Agilent, 2012), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), ATOMS (Dowty, 1993), OLEX2 (Dolomanov et al., 2009).
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Only a few phosphates in nature contain iron in both valence states. The more common minerals with these chemical features are barbosalite–lipscombite [FeIIFeIII2(PO4)2(OH)2], beraunite [FeIIFeIII5(PO4)4(OH)5.6H2O], rockbridgeite [FeIIFeIII4(PO4)3(OH)5] and whitmoreite [FeIIFeIII2(PO4)2(OH)2.4H2O]. They generally occur in granitic pegmatites as secondary minerals which are produced by the alteration of primary iron phosphates. Gorbunov et al. (1980) obtained the first synthetic iron phosphate with both FeII and FeIII, with the formula FeII3FeIII4(PO4)6. Redhammer et al. (2004) refined the structure of a similar compound containing a very small amount of sodium, Na0.1Fe7(PO4)3, and demonstrated that this phosphate was isotypic with the vanadate howerdevansite, NaCuIIFeIII2(VO4)6 (Hughes et al., 1988). Lightfoot & Cheetham (1986) and Vencato et al. (1994) have shown that the reduction of FeIII in FeII3FeIII4(PO4)6 can induce the formation of isostructural hydrogenphosphates, with compositions FeII7-xFeIIIx(PO4)2+x(PO3OH)4-x (0 < x < 4).
In order to explore the stability of lithium iron phosphates, we decided to perform hydrothermal experiments in the Li–FeII–FeIII (+PO4) system, between 673 and 973 K, under a pressure of 0.1 GPa. In these experiments, various iron phosphates crystallized as, for example, Fe3(PO4)2 (sarcopside-type), Fe7(PO4)6, Fe3(PO4)2(OH)2 and Fe4(PO4)3(OH)3 (Dal Bo, 2011). Fe7(PO4)6 is a stable phase between 673 and 973 K; electron-microprobe chemical analyses performed on 11 samples have shown variations of the Fe/P ratio from ca 7/6 to 6/6. In order to understand the variation of this ratio, single-crystal X-ray structural investigations were performed on two samples synthesized at 973 K (H.339 and H.347).
The present paper reports the crystal structure of FeII2.67FeIII4(PO4)5.35(HPO4)0.65 (H.339) and FeII2.23FeIII4(PO4)4.45(HPO4)1.55 (H.347). Both structures were refined in the space group P1 (No. 2) and are similar to those of corresponding iron phosphates and iron hydrogenphosphates reported in the literature (Redhammer et al., 2004; Vencato et al., 1994). The structures are characterized by isolated PO4 tetrahedra and four different types of Fe polyhedra. Fe1, Fe2 and Fe3 occur in octahedral environments, whereas Fe4 occurs in a fivefold distorted trigonal–bipyramid. Fe1, Fe2 and Fe4 are connected to each other by edge sharing to form infinite chains parallel to the [101] direction (Fig. 1). These chains are characterized by a stacking sequence ···Fe1—Fe1—Fe4—Fe2—Fe2···, and the Fe3 octahedra connect the chains in the b direction by sharing corners with the Fe4 and Fe1 sites. As can be seen in Fig. 2, the PO4 tetrahedra connect the chains together by corner sharing.
Refinement of the site-occupancy factors indicates that all Fe sites are fully occupied by iron, except Fe4 which contains 0.84 and 0.61 FeII in samples H.339 and H.347, respectively.
The charge deficit induced by this partial occupancy is compensated by the replacement of (PO4)3- by (HPO4)2-, according to the substitution mechanism FeII + 2(PO4)3- = vacancies + 2(HPO4)2-. Consequently, the general chemical formula of these phosphates can be expressed as FeII1 + 2xFeIII4(PO4)4x+2(HPO4)4–4x, in which x = 0.84 (sample H.339) or x = 0.61 (sample H.347). The substitution mechanism observed in the title compounds is completely different from that described by Lightfoot & Cheetham (1986) and Vencato et al. (1994), which corresponds to FeIII + (PO4)3- = FeII + (HPO4)2-. In this last case, the charge deficit is produced by reducing FeIII into FeII, whereas in samples H.339 and H.347, this deficit is rather produced by the appearance of vacancies on the Fe4 five-coordinated site.
Since Li was present in the starting material used for the synthesis experiments, we decided to perform another refinement in which the Fe4 site is occupied simultaneously by Fe and Li. This refinement shows a site population of 0.44 Li + 0.56 Fe, but the bond-valence sum of 1.41, calculated from the Fe4—O bond lengths, is in poor agreement with the expected value 1.56. Moreover, a detailed analysis of difference Fourier maps indicated the presence of one H atom, located at 0.77 Å from O6 in sample H.347, thus confirming the existence of HPO4 groups in these phosphates. In the final refinement cycle, we consequently adopted the most realistic model in which the Fe4 site is occupied by FeII and vacancies, without any significant amount of lithium.
The final site populations, calculated from the observed site occupancies and assuming charge balance, are FeIII on the Fe1 and Fe2 sites, FeII on the Fe3 site, and FeII plus vacancies on the Fe4 site. Bond-valence sums, calculated by using the empirical parameters of Brown & Altermatt (1985), confirm the distributions of FeII and FeIII among the different crystallographic sites. Indeed, the Fe1, Fe2, Fe3 and Fe4 bond-valence sums are 3.01, 3.07, 1.82 and 1.96 (H.339) or 3.09, 3.10, 2.07 and 1.94 (H.347), respectively. The bond-valence sums for P1, P2 and P3 are 4.92, 4.95 and 5.04 (H.339), or 4.93, 4.96, 5.03 (H.347), respectively.