Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270106028678/iz3009sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270106028678/iz3009Isup2.hkl | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270106028678/iz3009IIsup3.hkl |
Crystals of (I) were obtained by the self-flux method from KPO3 (5.17 g), K4P2O7 (7.14 g), CrPO4 (1.16 g) and Nb2O5 (1.85 g). An initial mixture was powdered in an agate mortar, placed in a 25 ml platinum crucible, and then exposed at 1323 K for 2 h under constant stirring every 0.5 h [`every 0.5 h' implies that stirring is not `constant'; please clarify] with a platinum mixer. The solution was cooled at a rate of 40 K h−1 to 1093 K. The rest of the glass was washed away with plenty of hot deionized water, adding 5% solutions of the bisubstituted salt of ethylenediaminetetraacetic acid. Among a significant number of druses there were well formed green crystals with a typical KTP morphology (Bolt & Bennema, 1990). Similarly, red crystals of (II) were grown from KPO3 (5.17 g), K4P2O7 (7.14 g), Fe2O3 (1.16 g) and Nb2O5 (1.85 g) in the same conditions as described for (I) above. The presence of iron, chromium, and niobium were determined using X-ray fluorescence analysis. The composition of the single crystals was verified using scanning electron microscopy.
The centrosymmetric group Pnna was chosen, with Rint = 0.053 for (I) and Rint = 0.039 for (II). No indication of twinning was revealed during data processing. Linear combination restraints were applied in the process of the Cr/Nb and Fe/Nb ratio refinement (Sheldrick, 1997).
For both compounds, data collection: CrysAlis CCD (Oxford Diffraction, 2005); cell refinement: CrysAlis CCD; data reduction: CrysAlis RED (Oxford Diffraction, 2005); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997). Molecular graphics: ORTEP-3 for Windows (Farrugia, 1997) and DIAMOND (Bradenburg, 2006) for (I); ORTEP-3 for Windows (Farrugia, 1997) and DIAMOND Bradenburg, 2006) for (II). For both compounds, software used to prepare material for publication: WinGX (Farrugia, 1999).
KCr0.5Nb0.5OPO4 | F(000) = 852 |
Mr = 222.53 | Dx = 3.335 Mg m−3 |
Orthorhombic, Pnna | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2a 2bc | Cell parameters from 320 reflections |
a = 12.849 (3) Å | θ = 15–25° |
b = 10.672 (2) Å | µ = 3.86 mm−1 |
c = 6.4635 (13) Å | T = 293 K |
V = 886.3 (3) Å3 | Prism, dark green |
Z = 8 | 0.4 × 0.15 × 0.06 mm |
Oxford Diffraction XCalibur-3 diffractometer | 1075 independent reflections |
Radiation source: sealed tube | 1066 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.036 |
ϕ and ω scans | θmax = 28°, θmin = 3.2° |
Absorption correction: multi-scan (Blessing, 1995) | h = −16→16 |
Tmin = 0.510, Tmax = 0.770 | k = −12→14 |
13131 measured reflections | l = −8→8 |
Refinement on F2 | 88 parameters |
Least-squares matrix: full | 1 restraint |
R[F2 > 2σ(F2)] = 0.050 | w = 1/[σ2(Fo2) + (0.0308P)2 + 16.1755P] where P = (Fo2 + 2Fc2)/3 |
wR(F2) = 0.114 | (Δ/σ)max < 0.001 |
S = 1.24 | Δρmax = 3.20 e Å−3 |
1075 reflections | Δρmin = −1.50 e Å−3 |
KCr0.5Nb0.5OPO4 | V = 886.3 (3) Å3 |
Mr = 222.53 | Z = 8 |
Orthorhombic, Pnna | Mo Kα radiation |
a = 12.849 (3) Å | µ = 3.86 mm−1 |
b = 10.672 (2) Å | T = 293 K |
c = 6.4635 (13) Å | 0.4 × 0.15 × 0.06 mm |
Oxford Diffraction XCalibur-3 diffractometer | 1075 independent reflections |
Absorption correction: multi-scan (Blessing, 1995) | 1066 reflections with I > 2σ(I) |
Tmin = 0.510, Tmax = 0.770 | Rint = 0.036 |
13131 measured reflections |
R[F2 > 2σ(F2)] = 0.050 | 1 restraint |
wR(F2) = 0.114 | w = 1/[σ2(Fo2) + (0.0308P)2 + 16.1755P] where P = (Fo2 + 2Fc2)/3 |
S = 1.24 | Δρmax = 3.20 e Å−3 |
1075 reflections | Δρmin = −1.50 e Å−3 |
88 parameters |
Experimental. X-ray fluorescence analysis: Philips PW1400 spectrometer. Scanning electron microscopy: REMMA 202M Link Systems microscope with a resolution of 150 eV for the 5.9 keV line. |
Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell e.s.d.'s are taken into account in the estimation of distances, angles and torsion angles |
x | y | z | Uiso*/Ueq | Occ. (<1) | |
Nb2 | 0.3811 (8) | 0.2500 (1) | 0.2500 (1) | 0.0076 | 0.796 |
Nb1 | 0.5000 (1) | 0.0000 (1) | 0.0000 (1) | 0.0078 | 0.204 |
Cr1 | 0.5000 (1) | 0.0000 (1) | 0.0000 (1) | 0.0078 | 0.796 |
P1 | 0.4331 (7) | 0.2500 (1) | 0.7500 (1) | 0.0095 | |
P2 | 0.2500 (1) | 0.0000 (1) | 0.0867 (2) | 0.0089 | |
Cr2 | 0.3811 (8) | 0.2500 (1) | 0.2500 (1) | 0.0076 | 0.204 |
O1 | 0.3457 (5) | −0.0174 (2) | −0.0512 (6) | 0.0112 | |
O2 | 0.4760 (4) | 0.1248 (5) | 0.2107 (2) | 0.0101 | |
O3 | 0.2613 (1) | 0.1160 (1) | 0.2276 (2) | 0.0146 | |
O4 | 0.5024 (4) | 0.1359 (9) | 0.7887 (4) | 0.0130 | |
O5 | 0.3625 (8) | 0.2245 (1) | 0.5622 (3) | 0.0140 | |
K1 | 0.1311 (2) | 0.0554 (3) | 0.5328 (8) | 0.0437 | 0.500 |
K2 | 0.1471 (5) | 0.1865 (2) | 0.5618 (9) | 0.0469 | 0.500 |
U11 | U22 | U33 | U12 | U13 | U23 | |
Nb2 | 0.010 (1) | 0.006 (1) | 0.006 (7) | 0.000 (1) | 0.000 (1) | −0.000 (5) |
Nb1 | 0.004 (9) | 0.007 (2) | 0.011 (2) | 0.000 (5) | 0.000 (5) | 0.003 (1) |
Cr1 | 0.004 (9) | 0.007 (2) | 0.011 (2) | 0.000 (5) | 0.000 (5) | 0.003 (1) |
P1 | 0.014 (9) | 0.007 (4) | 0.006 (1) | 0.000 (1) | 0.000 (1) | 0.001 (2) |
P2 | 0.007 (6) | 0.008 (4) | 0.010 (7) | −0.000 (6) | 0.000 (1) | 0.000 (1) |
Cr2 | 0.010 (1) | 0.006 (1) | 0.006 (7) | 0.000 (1) | 0.000 (1) | −0.000 (5) |
O1 | 0.008 (5) | 0.010 (4) | 0.014 (7) | 0.002 (6) | 0.001 (5) | −0.002 (6) |
O2 | 0.010 (6) | 0.012 (1) | 0.007 (6) | 0.003 (6) | −0.000 (9) | −0.002 (8) |
O3 | 0.012 (1) | 0.013 (8) | 0.017 (9) | −0.003 (5) | 0.004 (6) | −0.005 (8) |
O4 | 0.014 (8) | 0.010 (9) | 0.013 (4) | 0.006 (1) | 0.001 (5) | 0.004 (1) |
O5 | 0.013 (6) | 0.018 (1) | 0.010 (5) | −0.003 (3) | −0.001 (4) | −0.000 (3) |
K1 | 0.052 (9) | 0.051 (5) | 0.026 (5) | 0.018 (7) | 0.014 (7) | 0.007 (3) |
K2 | 0.023 (5) | 0.075 (4) | 0.041 (8) | −0.001 (1) | 0.010 (6) | −0.003 (1) |
K1—K2 | 1.426 (4) | Nb2—O2 | 1.825 (9) |
K1—O3 | 2.667 (6) | Nb2—O3 | 2.106 (7) |
K1—O2i | 2.696 (6) | Nb2—O5 | 2.050 (3) |
K1—O1ii | 2.734 (6) | Nb2—O2vi | 1.825 (9) |
K1—O4i | 2.792 (6) | Nb2—O3vi | 2.106 (7) |
K1—O5iii | 2.994 (6) | Cr1—O1 | 2.018 (1) |
K1—O3iii | 3.025 (6) | Cr1—O2 | 1.930 (1) |
K1—O4iii | 3.138 (6) | Cr1—O4viii | 1.992 (9) |
K1—O2iii | 3.152 (6) | Cr1—O1ix | 2.018 (1) |
K2—O3 | 2.717 (6) | Cr1—O2ix | 1.930 (1) |
K2—O2i | 2.726 (6) | Cr1—O4x | 1.992 (9) |
K2—O5 | 2.797 (6) | Cr2—O5 | 2.050 (3) |
K2—O4i | 2.981 (6) | Cr2—O2 | 1.825 (9) |
K2—O1ii | 3.085 (7) | Cr2—O3 | 2.106 (7) |
K2—O2iv | 3.133 (6) | Cr2—O5vi | 2.050 (3) |
K2—O1v | 3.162 (7) | Cr2—O2vi | 1.825 (9) |
K2—O3vi | 3.177 (6) | Cr2—O3vi | 2.106 (7) |
K2—O4vii | 3.189 (6) | P1—O4 | 1.529 (10) |
Nb1—O2 | 1.930 (1) | P1—O5 | 1.540 (8) |
Nb1—O4viii | 1.992 (9) | P1—O4xi | 1.529 (10) |
Nb1—O1ix | 2.018 (1) | P1—O5xi | 1.540 (8) |
Nb1—O2ix | 1.930 (1) | P2—O1 | 1.530 (6) |
Nb1—O4x | 1.992 (9) | P2—O3 | 1.5437 (14) |
Nb1—O1 | 2.018 (1) | P2—O1iii | 1.530 (6) |
Nb2—O5vi | 2.050 (3) | P2—O3iii | 1.5437 (14) |
O1—Nb1—O2 | 91.3 (1) | O1ix—Cr1—O2 | 88.6 (9) |
O1—Nb1—O4viii | 88.2 (8) | O2—Cr1—O2ix | 180.0 (1) |
O1—Nb1—O1ix | 180.0 (1) | O2—Cr1—O4x | 90.9 (6) |
O1—Nb1—O2ix | 88.6 (9) | O1ix—Cr1—O4viii | 91.7 (2) |
O1—Nb1—O4x | 91.7 (2) | O2ix—Cr1—O4viii | 90.9 (6) |
O2—Nb1—O4viii | 89.0 (4) | O4viii—Cr1—O4x | 180.0 (1) |
O1ix—Nb1—O2 | 88.6 (9) | O1ix—Cr1—O2ix | 91.3 (1) |
O2—Nb1—O2ix | 180.0 (1) | O1ix—Cr1—O4x | 88.2 (8) |
O2—Nb1—O4x | 90.9 (6) | O2ix—Cr1—O4x | 89.0 (4) |
O1ix—Nb1—O4viii | 91.7 (2) | O2—Cr2—O3vi | 173.7 (8) |
O2ix—Nb1—O4viii | 90.9 (6) | O2—Cr2—O5vi | 92.1 (8) |
O4viii—Nb1—O4x | 180.0 (1) | O3—Cr2—O5 | 83.8 (2) |
O1ix—Nb1—O2ix | 91.3 (1) | O2vi—Cr2—O3 | 173.7 (8) |
O1ix—Nb1—O4x | 88.2 (8) | O3—Cr2—O3vi | 86.0 (4) |
O2ix—Nb1—O4x | 89.0 (4) | O3—Cr2—O5vi | 86.4 (1) |
O2—Nb2—O3 | 88.9 (7) | O2vi—Cr2—O5 | 92.1 (8) |
O2—Nb2—O5 | 96.7 (5) | O3vi—Cr2—O5 | 86.4 (1) |
O2—Nb2—O2vi | 96.2 (4) | O5—Cr2—O5vi | 166.6 (1) |
O2—Nb2—O3vi | 173.7 (8) | O2vi—Cr2—O3vi | 88.9 (7) |
O2—Nb2—O5vi | 92.1 (8) | O2vi—Cr2—O5vi | 96.7 (5) |
O3—Nb2—O5 | 83.8 (2) | O3vi—Cr2—O5vi | 83.8 (2) |
O2vi—Nb2—O3 | 173.7 (8) | O2—Cr2—O3 | 88.9 (7) |
O3—Nb2—O3vi | 86.0 (4) | O2—Cr2—O5 | 96.7 (5) |
O3—Nb2—O5vi | 86.4 (1) | O2—Cr2—O2vi | 96.2 (4) |
O2vi—Nb2—O5 | 92.1 (8) | O4—P1—O5 | 109.4 (3) |
O3vi—Nb2—O5 | 86.4 (1) | O4—P1—O4xi | 108.7 (5) |
O5—Nb2—O5vi | 166.6 (1) | O4—P1—O5xi | 110.7 (8) |
O2vi—Nb2—O3vi | 88.9 (7) | O4xi—P1—O5 | 110.7 (8) |
O2vi—Nb2—O5vi | 96.7 (5) | O5—P1—O5xi | 107.8 (1) |
O3vi—Nb2—O5vi | 83.8 (2) | O4xi—P1—O5xi | 109.4 (3) |
O1—Cr1—O2 | 91.3 (1) | O1—P2—O3 | 111.43 (14) |
O1—Cr1—O4viii | 88.2 (8) | O1—P2—O1iii | 108.7 (4) |
O1—Cr1—O1ix | 180.0 (1) | O1—P2—O3iii | 108.7 (8) |
O1—Cr1—O2ix | 88.6 (9) | O1iii—P2—O3 | 108.7 (8) |
O1—Cr1—O4x | 91.7 (2) | O3—P2—O3iii | 107.6 (9) |
O2—Cr1—O4viii | 89.0 (4) | O1iii—P2—O3iii | 111.4 (3) |
Symmetry codes: (i) x−3/2, y, −z+1; (ii) −x+1/2, −y, z+1; (iii) −x+1/2, −y, z; (iv) −x−1, y−1/2, z−1/2; (v) x, −y+1/2, −z+1/2; (vi) −x+1/2, y+1/2, −z+1/2; (vii) −x−1, y−1/2, z−3/2; (viii) x, y, z−1; (ix) −x+1, −y, −z; (x) −x+1, −y, −z+1; (xi) −x+1/2, y+1/2, −z+3/2. |
KFe0.5Nb0.5OPO4 | F(000) = 860 |
Mr = 224.45 | Dx = 3.323 Mg m−3 |
Orthorhombic, Pnna | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2a 2bc | Cell parameters from 450 reflections |
a = 12.9675 (13) Å | θ = 15–26° |
b = 10.705 (3) Å | µ = 4.22 mm−1 |
c = 6.4638 (7) Å | T = 293 K |
V = 897.3 (3) Å3 | Prism, dark red |
Z = 8 | 0.2 × 0.15 × 0.1 mm |
Oxford Diffraction XCalibur-3 diffractometer | 1087 independent reflections |
Radiation source: sealed tube | 1021 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.027 |
ϕ and ω scans | θmax = 28.0°, θmin = 3.1° |
Absorption correction: multi-scan (Blessing, 1995) | h = −15→17 |
Tmin = 0.387, Tmax = 0.496 | k = −14→14 |
18570 measured reflections | l = −8→8 |
Refinement on F2 | 1 restraint |
Least-squares matrix: full | w = 1/[σ2(Fo2) + (0.P)2 + 22.555P] where P = (Fo2 + 2Fc2)/3 |
R[F2 > 2σ(F2)] = 0.048 | (Δ/σ)max < 0.001 |
wR(F2) = 0.113 | Δρmax = 1.47 e Å−3 |
S = 1.33 | Δρmin = −1.32 e Å−3 |
1087 reflections | Extinction correction: SHELXL, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
88 parameters | Extinction coefficient: 0.0048 (5) |
KFe0.5Nb0.5OPO4 | V = 897.3 (3) Å3 |
Mr = 224.45 | Z = 8 |
Orthorhombic, Pnna | Mo Kα radiation |
a = 12.9675 (13) Å | µ = 4.22 mm−1 |
b = 10.705 (3) Å | T = 293 K |
c = 6.4638 (7) Å | 0.2 × 0.15 × 0.1 mm |
Oxford Diffraction XCalibur-3 diffractometer | 1087 independent reflections |
Absorption correction: multi-scan (Blessing, 1995) | 1021 reflections with I > 2σ(I) |
Tmin = 0.387, Tmax = 0.496 | Rint = 0.027 |
18570 measured reflections |
R[F2 > 2σ(F2)] = 0.048 | 1 restraint |
wR(F2) = 0.113 | w = 1/[σ2(Fo2) + (0.P)2 + 22.555P] where P = (Fo2 + 2Fc2)/3 |
S = 1.33 | Δρmax = 1.47 e Å−3 |
1087 reflections | Δρmin = −1.32 e Å−3 |
88 parameters |
Experimental. X-ray fluorescence analysis: Philips PW1400 spectrometer. Scanning electron microscopy: REMMA 202M Link Systems microscope with a resolution of 150 eV for the 5.9 keV line. |
Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell e.s.d.'s are taken into account in the estimation of distances, angles and torsion angles |
x | y | z | Uiso*/Ueq | Occ. (<1) | |
Nb2 | 0.3810 (1) | 0.2500 (1) | 0.2500 (1) | 0.0094 | 0.869 |
Nb1 | 0.5000 (1) | 0.0000 (1) | 0.0000 (1) | 0.0112 | 0.131 |
Fe1 | 0.5000 (1) | 0.0000 (1) | 0.0000 (1) | 0.0112 | 0.869 |
P1 | 0.4329 (2) | 0.2500 (1) | 0.7500 (1) | 0.0097 | |
P2 | 0.2500 (1) | 0.0000 (1) | 0.0840 (1) | 0.0098 | |
Fe2 | 0.3810 (1) | 0.2500 (1) | 0.2500 (1) | 0.0094 | 0.131 |
O1 | 0.3451 (7) | −0.0178 (6) | −0.0514 (1) | 0.0139 | |
O2 | 0.4758 (1) | 0.1248 (5) | 0.2143 (8) | 0.0127 | |
O3 | 0.2625 (6) | 0.1151 (2) | 0.2267 (4) | 0.0153 | |
O4 | 0.5016 (8) | 0.3639 (3) | 0.7145 (1) | 0.0146 | |
O5 | 0.3624 (6) | 0.2270 (3) | 0.5627 (6) | 0.0152 | |
K1 | 0.1292 (1) | 0.0536 (4) | 0.5307 (6) | 0.0333 | 0.500 |
K2 | 0.1454 (1) | 0.1897 (8) | 0.5557 (9) | 0.0374 | 0.500 |
U11 | U22 | U33 | U12 | U13 | U23 | |
Nb2 | 0.010 (3) | 0.008 (4) | 0.009 (5) | 0.000 (1) | 0.000 (1) | −0.000 (1) |
Nb1 | 0.009 (6) | 0.010 (8) | 0.013 (2) | 0.000 (5) | 0.000 (6) | 0.002 (5) |
Fe1 | 0.009 (6) | 0.010 (8) | 0.013 (2) | 0.000 (5) | 0.000 (6) | 0.002 (5) |
P1 | 0.011 (7) | 0.009 (6) | 0.007 (9) | 0.000 (1) | 0.000 (1) | 0.001 (2) |
P2 | 0.008 (9) | 0.007 (7) | 0.012 (6) | −0.000 (8) | 0.000 (1) | 0.000 (1) |
Fe2 | 0.010 (3) | 0.008 (4) | 0.009 (5) | 0.000 (1) | 0.000 (1) | −0.000 (1) |
O1 | 0.012 (2) | 0.013 (7) | 0.015 (8) | 0.001 (2) | 0.003 (1) | −0.000 (7) |
O2 | 0.013 (6) | 0.012 (8) | 0.011 (6) | 0.003 (8) | −0.001 (4) | −0.004 (1) |
O3 | 0.013 (6) | 0.015 (4) | 0.017 (1) | −0.003 (9) | 0.003 (2) | −0.006 (8) |
O4 | 0.016 (7) | 0.013 (1) | 0.014 (1) | −0.004 (6) | −0.004 (8) | 0.004 (9) |
O5 | 0.014 (1) | 0.017 (4) | 0.014 (1) | −0.000 (5) | −0.000 (5) | −0.000 (1) |
K1 | 0.040 (3) | 0.039 (1) | 0.020 (3) | 0.011 (3) | 0.009 (9) | 0.003 (7) |
K2 | 0.024 (6) | 0.057 (7) | 0.030 (1) | −0.002 (1) | 0.008 (1) | −0.003 (4) |
K1—K2 | 1.481 (3) | Nb2—O3 | 2.113 (5) |
K1—O2i | 2.693 (7) | Nb2—O5 | 2.050 (7) |
K1—O3 | 2.700 (7) | Nb2—O2viii | 1.832 (6) |
K1—O1ii | 2.748 (7) | Nb2—O3viii | 2.113 (5) |
K1—O4iii | 2.774 (7) | Fe1—O1 | 2.044 (1) |
K1—O5iv | 3.013 (7) | Fe1—O2 | 1.950 (6) |
K1—O3iv | 3.016 (7) | Fe1—O4viii | 2.011 (2) |
K1—O2iv | 3.113 (7) | Fe1—O1ix | 2.044 (1) |
K1—O4v | 3.117 (7) | Fe1—O2ix | 1.950 (6) |
K2—O3 | 2.734 (7) | Fe1—O4x | 2.011 (2) |
K2—O2i | 2.743 (7) | Fe2—O5 | 2.050 (7) |
K2—O5 | 2.844 (7) | Fe2—O2 | 1.832 (6) |
K2—O4iii | 2.944 (7) | Fe2—O3 | 2.113 (5) |
K2—O1vi | 3.132 (8) | Fe2—O5viii | 2.050 (7) |
K2—O2vii | 3.134 (7) | Fe2—O2viii | 1.832 (6) |
K2—O4i | 3.162 (7) | Fe2—O3viii | 2.113 (5) |
K2—O3viii | 3.163 (7) | P1—O4 | 1.527 (7) |
Nb1—O2 | 1.950 (6) | P1—O5 | 1.537 (6) |
Nb1—O4viii | 2.011 (2) | P1—O4xi | 1.527 (7) |
Nb1—O1ix | 2.044 (1) | P1—O5xi | 1.537 (6) |
Nb1—O2ix | 1.950 (6) | P2—O1 | 1.524 (7) |
Nb1—O4x | 2.011 (2) | P2—O3 | 1.548 (3) |
Nb1—O1 | 2.044 (1) | P2—O1iv | 1.524 (7) |
Nb2—O5viii | 2.050 (7) | P2—O3iv | 1.548 (3) |
Nb2—O2 | 1.832 (6) | ||
O1—Nb1—O2 | 91.2 (3) | O1ix—Fe1—O2 | 88.7 (7) |
O1—Nb1—O4viii | 88.0 (7) | O2—Fe1—O2ix | 180.0 (1) |
O1—Nb1—O1ix | 180.0 (1) | O2—Fe1—O4x | 90.2 (7) |
O1—Nb1—O2ix | 88.7 (7) | O1ix—Fe1—O4viii | 91.9 (3) |
O1—Nb1—O4x | 91.9 (3) | O2ix—Fe1—O4viii | 90.2 (7) |
O2—Nb1—O4viii | 89.7 (3) | O4viii—Fe1—O4x | 180.0 (1) |
O1ix—Nb1—O2 | 88.7 (7) | O1ix—Fe1—O2ix | 91.2 (3) |
O2—Nb1—O2ix | 180.0 (1) | O1ix—Fe1—O4x | 88.0 (7) |
O2—Nb1—O4x | 90.2 (7) | O2ix—Fe1—O4x | 89.7 (3) |
O1ix—Nb1—O4viii | 91.9 (3) | O2—Fe2—O3viii | 174.7 (4) |
O2ix—Nb1—O4viii | 90.2 (7) | O2—Fe2—O5viii | 92.4 (3) |
O4viii—Nb1—O4x | 180.0 (1) | O3—Fe2—O5 | 84.4 (3) |
O1ix—Nb1—O2ix | 91.2 (3) | O2viii—Fe2—O3 | 174.7 (4) |
O1ix—Nb1—O4x | 88.0 (7) | O3—Fe2—O3viii | 86.7 (7) |
O2ix—Nb1—O4x | 89.7 (3) | O3—Fe2—O5viii | 85.7 (9) |
O2—Nb2—O3 | 88.8 (1) | O2viii—Fe2—O5 | 92.4 (3) |
O2—Nb2—O5 | 96.6 (1) | O3viii—Fe2—O5 | 85.7 (9) |
O2—Nb2—O2viii | 95.7 (6) | O5—Fe2—O5viii | 166.5 (3) |
O2—Nb2—O3viii | 174.7 (4) | O2viii—Fe2—O3viii | 88.8 (1) |
O2—Nb2—O5viii | 92.4 (3) | O2viii—Fe2—O5viii | 96.6 (1) |
O3—Nb2—O5 | 84.4 (3) | O3viii—Fe2—O5viii | 84.4 (3) |
O2viii—Nb2—O3 | 174.7 (4) | O2—Fe2—O3 | 88.8 (1) |
O3—Nb2—O3viii | 86.7 (7) | O2—Fe2—O5 | 96.6 (1) |
O3—Nb2—O5viii | 85.7 (9) | O2—Fe2—O2viii | 95.7 (6) |
O2viii—Nb2—O5 | 92.4 (3) | O4—P1—O5 | 110.9 (2) |
O3viii—Nb2—O5 | 85.7 (9) | O4—P1—O4xi | 108.6 (1) |
O5—Nb2—O5viii | 166.5 (3) | O4—P1—O5xi | 109.7 (3) |
O2viii—Nb2—O3viii | 88.8 (1) | O4xi—P1—O5 | 109.7 (3) |
O2viii—Nb2—O5viii | 96.6 (1) | O5—P1—O5xi | 107.0 (1) |
O3viii—Nb2—O5viii | 84.4 (3) | O4xi—P1—O5xi | 110.9 (2) |
O1—Fe1—O2 | 91.2 (3) | O1—P2—O3 | 110.9 (4) |
O1—Fe1—O4viii | 88.0 (7) | O1—P2—O1iv | 109.9 (4) |
O1—Fe1—O1ix | 180.0 (1) | O1—P2—O3iv | 109.1 (1) |
O1—Fe1—O2ix | 88.7 (7) | O1iv—P2—O3 | 109.1 (1) |
O1—Fe1—O4x | 91.9 (3) | O3—P2—O3iv | 106.8 (4) |
O2—Fe1—O4viii | 89.7 (3) | O1iv—P2—O3iv | 110.9 (1) |
Symmetry codes: (i) x−3/2, y, −z+1; (ii) −x+1/2, −y, z+1; (iii) x−3/2, −y−1/2, z−3/2; (iv) −x+1/2, −y, z; (v) −x+1/2, y−1/2, −z+3/2; (vi) −x+1/2, y+1/2, −z+1/2; (vii) x−3/2, −y−1/2, z−1/2; (viii) x, −y+1/2, −z+1/2; (ix) −x+1, −y, −z; (x) −x+1, y−3/2, z−3/2; (xi) x, −y+1/2, −z+3/2. |
Experimental details
(I) | (II) | |
Crystal data | ||
Chemical formula | KCr0.5Nb0.5OPO4 | KFe0.5Nb0.5OPO4 |
Mr | 222.53 | 224.45 |
Crystal system, space group | Orthorhombic, Pnna | Orthorhombic, Pnna |
Temperature (K) | 293 | 293 |
a, b, c (Å) | 12.849 (3), 10.672 (2), 6.4635 (13) | 12.9675 (13), 10.705 (3), 6.4638 (7) |
V (Å3) | 886.3 (3) | 897.3 (3) |
Z | 8 | 8 |
Radiation type | Mo Kα | Mo Kα |
µ (mm−1) | 3.86 | 4.22 |
Crystal size (mm) | 0.4 × 0.15 × 0.06 | 0.2 × 0.15 × 0.1 |
Data collection | ||
Diffractometer | Oxford Diffraction XCalibur-3 diffractometer | Oxford Diffraction XCalibur-3 diffractometer |
Absorption correction | Multi-scan (Blessing, 1995) | Multi-scan (Blessing, 1995) |
Tmin, Tmax | 0.510, 0.770 | 0.387, 0.496 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 13131, 1075, 1066 | 18570, 1087, 1021 |
Rint | 0.036 | 0.027 |
(sin θ/λ)max (Å−1) | 0.661 | 0.660 |
Refinement | ||
R[F2 > 2σ(F2)], wR(F2), S | 0.050, 0.114, 1.24 | 0.048, 0.113, 1.33 |
No. of reflections | 1075 | 1087 |
No. of parameters | 88 | 88 |
No. of restraints | 1 | 1 |
w = 1/[σ2(Fo2) + (0.0308P)2 + 16.1755P] where P = (Fo2 + 2Fc2)/3 | w = 1/[σ2(Fo2) + (0.P)2 + 22.555P] where P = (Fo2 + 2Fc2)/3 | |
Δρmax, Δρmin (e Å−3) | 3.20, −1.50 | 1.47, −1.32 |
Computer programs: CrysAlis CCD (Oxford Diffraction, 2005), CrysAlis CCD, CrysAlis RED (Oxford Diffraction, 2005), SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), ORTEP-3 for Windows (Farrugia, 1997) and DIAMOND (Bradenburg, 2006), ORTEP-3 for Windows (Farrugia, 1997) and DIAMOND Bradenburg, 2006), WinGX (Farrugia, 1999).
K1—K2 | 1.426 (4) | K2—O2iv | 3.133 (6) |
K1—O3 | 2.667 (6) | K2—O1v | 3.162 (7) |
K1—O2i | 2.696 (6) | K2—O3vi | 3.177 (6) |
K1—O1ii | 2.734 (6) | K2—O4vii | 3.189 (6) |
K1—O4i | 2.792 (6) | Cr1—O1 | 2.018 (1) |
K1—O5iii | 2.994 (6) | Cr1—O2 | 1.930 (1) |
K1—O3iii | 3.025 (6) | Cr1—O4viii | 1.992 (9) |
K1—O4iii | 3.138 (6) | Cr2—O5 | 2.050 (3) |
K1—O2iii | 3.152 (6) | Cr2—O2 | 1.825 (9) |
K2—O3 | 2.717 (6) | Cr2—O3 | 2.106 (7) |
K2—O2i | 2.726 (6) | P1—O4 | 1.529 (10) |
K2—O5 | 2.797 (6) | P1—O5 | 1.540 (8) |
K2—O4i | 2.981 (6) | P2—O1 | 1.530 (6) |
K2—O1ii | 3.085 (7) | P2—O3 | 1.5437 (14) |
Symmetry codes: (i) x−3/2, y, −z+1; (ii) −x+1/2, −y, z+1; (iii) −x+1/2, −y, z; (iv) −x−1, y−1/2, z−1/2; (v) x, −y+1/2, −z+1/2; (vi) −x+1/2, y+1/2, −z+1/2; (vii) −x−1, y−1/2, z−3/2; (viii) −x+1, −y, −z+1. |
K1—K2 | 1.481 (3) | K2—O2vii | 3.134 (7) |
K1—O2i | 2.693 (7) | K2—O4i | 3.162 (7) |
K1—O3 | 2.700 (7) | K2—O3viii | 3.163 (7) |
K1—O1ii | 2.748 (7) | Fe1—O1 | 2.044 (1) |
K1—O4iii | 2.774 (7) | Fe1—O2 | 1.950 (6) |
K1—O5iv | 3.013 (7) | Fe1—O4viii | 2.011 (2) |
K1—O3iv | 3.016 (7) | Fe2—O5 | 2.050 (7) |
K1—O2iv | 3.113 (7) | Fe2—O2 | 1.832 (6) |
K1—O4v | 3.117 (7) | Fe2—O3 | 2.113 (5) |
K2—O3 | 2.734 (7) | P1—O4 | 1.527 (7) |
K2—O2i | 2.743 (7) | P1—O5 | 1.537 (6) |
K2—O5 | 2.844 (7) | P2—O1 | 1.524 (7) |
K2—O4iii | 2.944 (7) | P2—O3 | 1.548 (3) |
K2—O1vi | 3.132 (8) |
Symmetry codes: (i) x−3/2, y, −z+1; (ii) −x+1/2, −y, z+1; (iii) x−3/2, −y−1/2, z−3/2; (iv) −x+1/2, −y, z; (v) −x+1/2, y−1/2, −z+3/2; (vi) −x+1/2, y+1/2, −z+1/2; (vii) x−3/2, −y−1/2, z−1/2; (viii) x, −y+1/2, −z+1/2. |
Compounds with KTiOPO4 (KTP) structure have possible nonlinear optical properties (Zumsteg et al., 1976). The Nb5+-doped KTP crystal shows considerably improved secondary harmonic generation (SHG) (Thomas & Watts, 1990; Zhang et al., 2004). There are aliovalent isomorphs constructed on the principle xM5+ + yM2+ = zM4+, where M denotes a cation at an octahedral site. Such modeling for the replacement of Ti4+ ions is observed in KMg0.33Nb0.67OPO4 (McCarron & Calabrese, 1993). The Nb(Mg)—O bond lengths peculiar to the undistorted octahedron explain the small value of the SHG intensity. The Rietveld analysis of kV0.5Nb0.5OPO4 (Rangan et al., 1998) indicated a selective occupation of Nb at Ti1 and that of V at Ti2 sites. The Nb1(V1)O6 octahedron is more distorted than Nb2(V2)O6. Compounds with general formula KM0.5M'0.5OPO4 (M = NbV and TaV; M' = TiIII, VIII, CrIII and FeIII) and their derivatives, such as K0.5M0.5M'0.5OPO4 (M = NbV and TaV; M ' = TiIV and VIV) were also investigated by powder diffraction (Gopalakrishnan et al., 1994).
The present research is devoted to studying new isomorphic KTP compounds, viz. KCr0.5Nb0.5OPO4, (I), and KFe0.5Nb0.5OPO4, (II). In these compounds, M1O6 and M2O6 octahedra are linked to each other via a common O2 atom and form an infinite chain along the [011] direction. The polyhedral linkage is based on the cis–trans arrangement as observed in KTP (Tordjman et al., 1974). In both structures, disorder of Nb and Cr (or Fe) atoms is observed at octahedral sites. Nb atoms preferentially occupy M2 sites, while Cr or Fe atoms occupy M1 sites. The M2O6 octahedra arranged in the cis-like principle along the chain are considerably distorted; the M2—O bond lengths are in the range 1.826 (4)–2.107 (4) Å for (I) and 1.833 (5)–2.114 (5) Å for (II) (Tables 1 and 2). The M2—O2 bond length along the chain is much shorter than the others. The M1O6 octahedron is more regular than M2O6, with M1—O bond lengths of 1.930 (4)–2.044 (5) Å.
The three-dimensional structure arises from the [MO6]∞ chains interlinked by PO4 tetrahedra. Each PO4 tetrahedron has a symmetry of mm2. The anionic framework contains cavities in which K+ ions are placed. The K-site splitting into K1 and K2 is observed for both (I) and (II). The split K1 and K2 sites have site occupancies of 0.5 and are distant from one another by 1.426 (7) Å for (I) and 1.481 (7) Å for (II). The K atoms are coordinated by eight O atoms with K—O distances less than 3.2 Å. Four O atoms, namely, O1, O2, O3 and O4, lie practically on a plane parallel to (010) (Fig. 2), and are common for both the K1 and K2 environments with short K—O distances [2.666 (6)–2.792 (6) for (I) and 2.693?(6)–2.773?(7) Å for (II)]. The other O atoms around K are distant up to 3.188 (7) Å in (I) and 3.163 (7) Å in (II). A similar splitting has been reported for the K atom in KTP structures (Thomas & Watts, 1990; Norberg & Ishizawa, 2005).