Melilite-like modulation and temperature-dependent evolution in the framework structure of K₂Sc[Si₂O₆]F

The crystal structure of synthetic K₂Sc[Si₂O₆]F has been solved and refined as an incommensurately modulated structure in (3 + 2)-dimensional superspace. This paper describes the tetragonal structure in the superspace group P4₂/mnm(α,α,0)000s(−α,α,0)0000 [a = 8.9878 (1), c = 8.2694 (2) Å, V = 668.01 (2) ų] with modulation wavevectors q₁ = 0.2982 (4)(a* + b*) and q₂ = 0.2982 (4)(−a* + b*). Structure refinement taking into account the modulation of positional and ADP parameters for all atoms from 3074 observed main hkl00 and satellite reflections hklmn of first order with single, m·n = 0, and mixed, m·n = ±1, indices converged to a final R value of 0.0514. The structure is a mixed octahedral–tetrahedral framework composed of [ScO₄F₂] octahedra, [Si₄O₁₂] rings and K in variable coordination. Due to the modulation the O atoms move into and out of the first coordination sphere of K leading to a minimum of five and a maximum of 10 interatomic K—O distances up to 3.1 Å. Although this feature is comparable to observations in modulated fresnoite and melilite group compounds, these structures differ from K₂Sc[Si₂O₆]F with respect to their topology. On temperature increase the intensity of the satellite reflections decreases until they disappear just above 443 K. The high-temperature normal structure, in space group P4₂/mnm, is identical to the room-temperature average structure of K₂Sc[Si₂O₆]F.

Computing details

Data collection: CrysAlis PRO, Agilent Technologies, Version 1.171.35.19 (release 27-10-2011 CrysAlis171 .NET) (compiled Oct 27 2011,15:02:11) for I_rt; CrysAlis PRO, Agilent Technologies, Version 1.171.36.20 (release 27-06-2012 CrysAlis171 .NET) (compiled Jul 11 2012,15:38:31) for II_rt_incom, III_223K, III_173K. Cell refinement: CrysAlis PRO, Agilent Technologies, Version 1.171.35.19 (release 27-10-2011 CrysAlis171 .NET) (compiled Oct 27 2011,15:02:11) for I_rt; CrysAlis PRO, Agilent Technologies, Version 1.171.36.20 (release 27-06-2012 CrysAlis171 .NET) (compiled Jul 11 2012,15:38:31) for II_rt_incom, III_223K, III_173K. Data reduction: CrysAlis PRO, Agilent Technologies, Version 1.171.35.19 (release 27-10-2011 CrysAlis171 .NET) (compiled Oct 27 2011,15:02:11) for I_rt; CrysAlis PRO, Agilent Technologies, Version 1.171.36.20 (release 27-06-2012 CrysAlis171 .NET) (compiled Jul 11 2012,15:38:31) for II_rt_incom, III_223K, III_173K.

(I_rt)

Crystal data

FK2O6ScSi2	F(000) = 576
Mr = 294.3	Dx = 2.935 Mg m^−3
Tetragonal, P42/m21/n2/m	Mo Kα radiation, λ = 0.7107 Å
Hall symbol: -P 4n;-2n	Cell parameters from 3764 reflections
a = 8.9780 (2) Å	θ = 3.2–28.3°
c = 8.2608 (3) Å	µ = 2.72 mm^−1
V = 665.86 (3) Å^3	T = 293 K
Z = 4

Data collection

Xcalibur, Ruby, Gemini ultra diffractometer	473 independent reflections
Radiation source: Enhance (Mo) X-ray Source	457 reflections with I > 3σ(I)
Graphite monochromator	Rint = 0.024
Detector resolution: 10.3575 pixels mm^-1	θmax = 28.4°, θmin = 3.2°
ω scans	h = −11→11
Absorption correction: multi-scan CrysAlisPro, Agilent Technologies, Version 1.171.35.19 (release 27-10-2011 CrysAlis171 .NET) (compiled Oct 27 2011,15:02:11) Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm.	k = −9→12
Tmin = 0.655, Tmax = 1	l = −11→10
4745 measured reflections

Refinement

Refinement on F	0 restraints
R[F^2 > 2σ(F^2)] = 0.035	0 constraints
wR(F^2) = 0.047	Weighting scheme based on measured s.u.'s w = 1/(σ^2(F) + 0.0001F^2)
S = 3.77	(Δ/σ)max = 0.009
473 reflections	Δρmax = 0.46 e Å^−3
38 parameters	Δρmin = −1.56 e Å^−3

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
Sc	0.5	0	0.25	0.0037 (2)
K1	0.79325 (8)	0.20675 (8)	0	0.0201 (3)
K2	0.34266 (8)	0.34266 (8)	0	0.0314 (3)
Si	0.12239 (6)	0.12239 (6)	0.19665 (9)	0.0043 (2)
O1	0	0	0.2594 (3)	0.0184 (9)
O2	0.1163 (2)	0.1163 (2)	0	0.0200 (8)
F	0.5	0	0	0.0197 (9)
O3	0.0725 (2)	0.28126 (17)	0.2593 (2)	0.0234 (6)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Sc	0.0045 (3)	0.0045 (3)	0.0020 (5)	0	0	0
K1	0.0250 (4)	0.0250 (4)	0.0101 (5)	0.0144 (4)	0	0
K2	0.0408 (5)	0.0408 (5)	0.0124 (6)	−0.0332 (6)	0	0
Si	0.0050 (3)	0.0050 (3)	0.0030 (5)	0.0013 (3)	−0.00030 (18)	−0.00030 (18)
O1	0.0242 (14)	0.0242 (14)	0.0068 (16)	−0.0167 (13)	0	0
O2	0.0276 (12)	0.0276 (12)	0.0048 (15)	−0.0142 (14)	0	0
F	0.0377 (18)	0.0187 (15)	0.0028 (14)	0.0021 (10)	0	0
O3	0.0380 (11)	0.0083 (8)	0.0240 (10)	0.0094 (8)	−0.0065 (8)	−0.0056 (6)

Bond lengths (Å)

Sc—F	2.0652 (2)	K1—O3^viii	2.8091 (19)
Sc—F^i	2.0652 (2)	K2—O1^ix	2.818 (2)
Sc—O3^ii	2.0704 (16)	K2—O1^x	2.818 (2)
Sc—O3^iii	2.0704 (16)	K2—O2	2.874 (2)
Sc—O3^iv	2.0704 (16)	Si—O1	1.6381 (10)
Sc—O3^v	2.0704 (16)	Si—O2	1.6264 (7)
K1—O3^vi	2.8091 (19)	Si—O3	1.5820 (17)
K1—O3^iii	2.8091 (19)	Si—O3^v	1.5820 (17)
K1—O3^vii	2.8091 (19)

Symmetry codes: (i) −y+1/2, x−1/2, z+1/2; (ii) −x+1/2, y−1/2, −z+1/2; (iii) x+1/2, −y+1/2, −z+1/2; (iv) −y+1, −x, z; (v) y, x, z; (vi) y+1/2, −x+1/2, z−1/2; (vii) y+1/2, −x+1/2, −z+1/2; (viii) x+1/2, −y+1/2, z−1/2; (ix) −y+1/2, x+1/2, z−1/2; (x) −x+1/2, y+1/2, −z+1/2.

(II_rt_incom)

Crystal data

FK2O6ScSi2	F(000) = 576
Mr = 294.3	Dx = 2.926 Mg m^−3
Tetragonal, P42/m21/n2/m†	Mo Kα radiation, λ = 0.71069 Å
q1 = 0.298200a* + 0.298200b*; q2 = -0.298200a* + 0.298200b*	Cell parameters from 6650 reflections
a = 8.9878 (1) Å	θ = 3–23.2°
c = 8.2694 (2) Å	µ = 2.71 mm^−1
V = 668.01 (2) Å^3	T = 293 K
Z = 4	0.36 × 0.23 × 0.09 mm

† Symmetry operations: (1) x₁, x₂, x₃, x₄, x₅; (2) −x₁, −x₂, x₃, −x₄, −x₅; (3) −x₂+1/2, x₁+1/2, x₃+1/2, −x₅+1/2, x₄+1/2; (4) x₂+1/2, −x₁+1/2, x₃+1/2, x₅+1/2, −x₄+1/2; (5) −x₁+1/2, x₂+1/2, −x₃+1/2, x₅, x₄; (6) x₁+1/2, −x₂+1/2, −x₃+1/2, −x₅, −x₄; (7) x₂, x₁, −x₃, x₄+1/2, −x₅+1/2; (8) −x₂, −x₁, −x₃, −x₄+1/2, x₅+1/2; (9) −x₁, −x₂, −x₃, −x₄, −x₅; (10) x₁, x₂, −x₃, x₄, x₅; (11) x₂+1/2, −x₁+1/2, −x₃+1/2, x₅+1/2, −x₄+1/2; (12) −x₂+1/2, x₁+1/2, −x₃+1/2, −x₅+1/2, x₄+1/2; (13) x₁+1/2, −x₂+1/2, x₃+1/2, −x₅, −x₄; (14) −x₁+1/2, x₂+1/2, x₃+1/2, x₅, x₄; (15) −x₂, −x₁, x₃, −x₄+1/2, x₅+1/2; (16) x₂, x₁, x₃, x₄+1/2, −x₅+1/2.

Data collection

Xcalibur, Ruby, Gemini ultra diffractometer	3223 independent reflections
Radiation source: Enhance (Mo) X-ray Source	3074 reflections with I > 3σ(I)
Graphite monochromator	Rint = 0.059
Detector resolution: 10.3575 pixels mm^-1	θmax = 26.7°, θmin = 1.4°
ω scans	h = −11→11
Absorption correction: multi-scan CrysAlisPro, Agilent Technologies, Version 1.171.36.20 (release 27-06-2012 CrysAlis171 .NET) (compiled Jul 11 2012,15:38:31) Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm.	k = −11→11
Tmin = 0.649, Tmax = 1	l = −10→10
43219 measured reflections

Refinement

Refinement on F	0 constraints
R[F^2 > 2σ(F^2)] = 0.052	Weighting scheme based on measured s.u.'s w = 1/(σ^2(F) + 0.0001F^2)
wR(F^2) = 0.064	(Δ/σ)max = 0.140
S = 4.21	Δρmax = 0.79 e Å^−3
3223 reflections	Δρmin = −0.75 e Å^−3
268 parameters	Extinction correction: B-C type 1 Gaussian isotropic (Becker & Coppens, 1974)
0 restraints	Extinction coefficient: 76000 (17000)

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
Sc	0.5	0	0.25	0.00838 (13)
K1	0.79314 (4)	0.20686 (4)	0	0.02308 (13)
K2	0.34293 (4)	0.34293 (4)	0	0.03292 (14)
Si	0.12224 (3)	0.12224 (3)	0.19667 (5)	0.00955 (12)
O1	0	0	0.25974 (18)	0.0182 (3)
O2	0.11643 (12)	0.11643 (12)	0	0.0217 (3)
F	0.5	0	0	0.0235 (4)
O3	0.07264 (8)	0.28094 (9)	0.25906 (8)	0.02148 (19)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Sc	0.0090 (2)	0.0090 (2)	0.0072 (3)	0	0	0
K1	0.0263 (2)	0.0263 (2)	0.0167 (3)	0.00903 (16)	0	0
K2	0.0402 (2)	0.0402 (2)	0.0184 (3)	−0.0235 (2)	0	0
Si	0.01040 (19)	0.01040 (19)	0.0078 (2)	0.00047 (11)	−0.00024 (7)	−0.00024 (7)
O1	0.0199 (5)	0.0199 (5)	0.0149 (8)	−0.0093 (4)	0	0
O2	0.0281 (5)	0.0281 (5)	0.0089 (6)	−0.0091 (5)	0	0
F	0.0322 (7)	0.0296 (8)	0.0086 (7)	−0.0030 (5)	0	0
O3	0.0266 (3)	0.0132 (3)	0.0247 (4)	0.0046 (2)	−0.0014 (2)	−0.0033 (2)

Geometric parameters (Å, º)

	Average	Minimum	Maximum
K2—O3^i	3.074 (2)	2.897 (2)	3.376 (2)
K2—O3^ii	3.084 (2)	2.897 (2)	3.376 (2)
K2—O3^iii	3.074 (2)	2.897 (2)	3.376 (2)
K2—O3^iv	3.084 (2)	2.897 (2)	3.376 (2)
O2^v—K1—O2^vi	58.72 (9)	57.83 (9)	59.60 (9)
O3—K2—O3^i	105.76 (6)	99.71 (6)	111.89 (7)
O3—K2—O3^ii	90.52 (6)	83.99 (6)	96.27 (6)
O3—K2—O3^vii	99.92 (6)	98.07 (6)	101.87 (6)
O3—K2—O3^viii	81.50 (6)	74.10 (6)	88.81 (7)
O3—K2—O3^iii	55.02 (5)	51.10 (5)	58.83 (6)
O3—K2—O3^iv	148.76 (7)	144.06 (7)	154.44 (6)
O3—K2—O3^ix	47.38 (5)	46.52 (5)	48.24 (5)
O3^i—K2—O3^ii	154.67 (7)	153.64 (7)	155.68 (8)
O3^i—K2—O3^vii	90.68 (6)	83.99 (6)	96.27 (6)
O3^i—K2—O3^viii	55.02 (6)	51.10 (5)	58.83 (6)
O3^i—K2—O3^iii	80.67 (7)	76.59 (6)	83.47 (7)
O3^i—K2—O3^iv	93.77 (6)	92.50 (6)	94.96 (5)
O3^i—K2—O3^ix	148.94 (7)	144.06 (7)	154.44 (6)
O3^ii—K2—O3^vii	105.60 (6)	99.71 (6)	111.89 (7)
O3^ii—K2—O3^viii	148.76 (7)	144.06 (7)	154.44 (6)
O3^ii—K2—O3^iii	93.77 (6)	92.50 (6)	94.96 (5)
O3^ii—K2—O3^iv	80.73 (7)	76.59 (6)	83.47 (7)
O3^ii—K2—O3^ix	54.84 (6)	51.10 (5)	58.83 (6)
O3^vii—K2—O3^viii	47.38 (5)	46.52 (5)	48.24 (5)
O3^vii—K2—O3^iii	148.94 (7)	144.06 (7)	154.44 (6)
O3^vii—K2—O3^iv	54.84 (5)	51.10 (5)	58.83 (6)
O3^vii—K2—O3^ix	81.41 (6)	74.10 (6)	88.81 (7)
O3^viii—K2—O3^iii	105.76 (6)	99.71 (6)	111.89 (7)
O3^viii—K2—O3^iv	90.52 (6)	83.99 (6)	96.27 (6)
O3^viii—K2—O3^ix	99.92 (6)	98.07 (6)	101.87 (6)
O3^iii—K2—O3^iv	154.67 (7)	153.64 (7)	155.68 (8)
O3^iii—K2—O3^ix	90.68 (6)	83.99 (6)	96.27 (6)
O3^iv—K2—O3^ix	105.60 (6)	99.71 (6)	111.89 (7)
K1^x—O2—K1^vi	121.24 (11)	117.84 (10)	124.67 (11)
K1^x—O2—O2^xi	60.53 (9)	57.77 (9)	63.97 (9)
K1^vi—O2—O2^xi	60.72 (9)	57.77 (9)	63.97 (9)

Symmetry codes: (i) −x₂+1/2, x₁+1/2, x₃−1/2, −x₅+1/2, x₄+1/2; (ii) x₁+1/2, −x₂+1/2, −x₃+1/2, −x₅, −x₄; (iii) −x₂+1/2, x₁+1/2, −x₃+1/2, −x₅+1/2, x₄+1/2; (iv) x₁+1/2, −x₂+1/2, x₃−1/2, −x₅, −x₄; (v) x₁+1, x₂, x₃, x₄, x₅; (vi) −x₁+1, −x₂, x₃, −x₄, −x₅; (vii) x₂, x₁, −x₃, x₄+1/2, −x₅+1/2; (viii) x₁, x₂, −x₃, x₄, x₅; (ix) x₂, x₁, x₃, x₄+1/2, −x₅+1/2; (x) x₁−1, x₂, x₃, x₄, x₅; (xi) −x₁, −x₂, x₃, −x₄, −x₅.

(II_473K)

Crystal data

FK2O6ScSi2	Z = 4
Mr = 294.3	F(000) = 576
Tetragonal, P42/m21/n2/m	Dx = 2.920 Mg m^−3
Hall symbol: -P 4n;-2n	Mo Kα radiation, λ = 0.71069 Å
a = 8.9939 (5) Å	µ = 2.71 mm^−1
c = 8.2758 (7) Å	T = 293 K
V = 669.43 (8) Å^3

Data collection

IPDS Stoe diffractometer	401 reflections with I > 3σ(I)
Radiation source: X-ray tube	Rint = 0.053
Graphite monochromator	θmax = 26.7°, θmin = 3.2°
??integration method?? scans	h = −11→11
4724 measured reflections	k = −11→11
406 independent reflections	l = −10→10

Refinement

Refinement on F	0 restraints
R[F^2 > 2σ(F^2)] = 0.026	0 constraints
wR(F^2) = 0.038	Weighting scheme based on measured s.u.'s w = 1/(σ^2(F) + 0.0001F^2)
S = 3.59	(Δ/σ)max = 0.018
406 reflections	Δρmax = 0.40 e Å^−3
38 parameters	Δρmin = −0.89 e Å^−3

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
Sc1	0.5	0	0.25	0.0098 (2)
Si	0.12240 (5)	0.12240 (5)	0.19636 (6)	0.01029 (19)
K1	0.79357 (6)	0.20643 (6)	0	0.0300 (2)
K2	0.34265 (7)	0.34265 (7)	0	0.0415 (3)
O2bz	0.1163 (2)	0.1163 (2)	0	0.0292 (6)
Obxx	0	0	0.2592 (3)	0.0241 (7)
F	0.5	0	0.5	0.0281 (8)
Ot	0.07257 (17)	0.28140 (13)	0.25854 (15)	0.0255 (4)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Sc1	0.0112 (3)	0.0112 (3)	0.0070 (4)	0	0	0
Si	0.0113 (3)	0.0113 (3)	0.0083 (4)	0.0002 (2)	−0.00030 (13)	−0.00030 (13)
K1	0.0344 (4)	0.0344 (4)	0.0211 (4)	0.0133 (4)	0	0
K2	0.0501 (5)	0.0501 (5)	0.0243 (5)	−0.0311 (5)	0	0
O2bz	0.0398 (10)	0.0398 (10)	0.0079 (11)	−0.0147 (12)	0	0
Obxx	0.0287 (11)	0.0287 (11)	0.0148 (13)	−0.0147 (10)	0	0
F	0.0341 (14)	0.0424 (15)	0.0079 (11)	0.0047 (9)	0	0
Ot	0.0348 (7)	0.0140 (6)	0.0277 (8)	0.0066 (5)	−0.0022 (6)	−0.0042 (4)

Geometric parameters (Å, º)

Sc1—F	2.0689 (3)	Si—Ot^v	1.5845 (13)
Sc1—F^i	2.0689 (3)	K1—Ot^vi	2.8206 (15)
Sc1—Ot^ii	2.0728 (13)	K1—Ot^iii	2.8206 (15)
Sc1—Ot^iii	2.0728 (13)	K1—Ot^vii	2.8206 (15)
Sc1—Ot^iv	2.0728 (13)	K1—Ot^viii	2.8206 (15)
Sc1—Ot^v	2.0728 (13)	K2—O2bz	2.8788 (19)
Si—O2bz	1.6269 (6)	K2—Obxx^ix	2.8245 (17)
Si—Obxx	1.6413 (8)	K2—Obxx^x	2.8245 (17)
Si—Ot	1.5845 (13)
F—Sc1—F^i	180.0 (5)	O2bz—Si—Obxx	105.74 (10)
F—Sc1—Ot^ii	91.95 (3)	O2bz—Si—Ot	110.20 (8)
F—Sc1—Ot^iii	91.95 (3)	O2bz—Si—Ot^v	110.20 (8)
F—Sc1—Ot^iv	88.05 (3)	Obxx—Si—Ot	108.23 (7)
F—Sc1—Ot^v	88.05 (3)	Obxx—Si—Ot^v	108.23 (7)
F^i—Sc1—Ot^ii	88.05 (3)	Ot—Si—Ot^v	113.89 (8)
F^i—Sc1—Ot^iii	88.05 (3)	Ot^vi—K1—Ot^iii	116.57 (4)
F^i—Sc1—Ot^iv	91.95 (3)	Ot^vi—K1—Ot^vii	90.22 (4)
F^i—Sc1—Ot^v	91.95 (3)	Ot^vi—K1—Ot^viii	56.18 (4)
Ot^ii—Sc1—Ot^iii	176.09 (5)	Ot^iii—K1—Ot^vii	56.18 (4)
Ot^ii—Sc1—Ot^iv	90.07 (6)	Ot^iii—K1—Ot^viii	90.22 (4)
Ot^ii—Sc1—Ot^v	90.07 (6)	Ot^vii—K1—Ot^viii	116.57 (4)
Ot^iii—Sc1—Ot^iv	90.07 (6)	O2bz—K2—Obxx^ix	135.12 (3)
Ot^iii—Sc1—Ot^v	90.07 (6)	O2bz—K2—Obxx^x	135.12 (3)
Ot^iv—Sc1—Ot^v	176.09 (5)	Obxx^ix—K2—Obxx^x	89.76 (5)

Symmetry codes: (i) −y+1/2, x−1/2, z−1/2; (ii) −x+1/2, y−1/2, −z+1/2; (iii) x+1/2, −y+1/2, −z+1/2; (iv) −y+1, −x, z; (v) y, x, z; (vi) y+1/2, −x+1/2, z−1/2; (vii) y+1/2, −x+1/2, −z+1/2; (viii) x+1/2, −y+1/2, z−1/2; (ix) −y+1/2, x+1/2, z−1/2; (x) −x+1/2, y+1/2, −z+1/2.

(II_rt)

Crystal data

FK2O6ScSi2	Z = 4
Mr = 294.3	F(000) = 576
Tetragonal, P42/m21/n2/m	Dx = 2.926 Mg m^−3
Hall symbol: -P 4n;-2n	Mo Kα radiation, λ = 0.71069 Å
a = 8.9878 (1) Å	µ = 2.71 mm^−1
c = 8.2694 (2) Å	T = 293 K
V = 668.01 (2) Å^3

Data collection

Radiation source: X-ray tube	θmax = 26.6°, θmin = 3.2°
3100 measured reflections	h = −11→11
264 independent reflections	k = −11→11
264 reflections with I > 3σ(I)	l = −10→10
Rint = 0.053

Refinement

Refinement on F	0 constraints
R[F^2 > 2σ(F^2)] = 0.029	Weighting scheme based on measured s.u.'s w = 1/(σ^2(F) + 0.0001F^2)
wR(F^2) = 0.053	(Δ/σ)max = 0.027
S = 3.95	Δρmax = 0.19 e Å^−3
264 reflections	Δρmin = −0.24 e Å^−3
40 parameters	Extinction correction: B-C type 1 Gaussian isotropic (Becker & Coppens, 1974)
0 restraints	Extinction coefficient: 100000 (30000)

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
Sc	0.5	0	0.25	0.0087 (3)
K1	0.79325 (5)	0.20675 (5)	0	0.0256 (4)
K2	0.34263 (6)	0.34263 (6)	0	0.0365 (4)
Si	0.12233 (4)	0.12233 (4)	0.19652 (6)	0.0093 (3)
O1	0	0	0.2604 (3)	0.0237 (8)
O2	0.11596 (17)	0.11596 (17)	0	0.0239 (6)
F	0.5	0	0	0.0249 (9)
O3	0.07211 (18)	0.28113 (15)	0.25936 (14)	0.0281 (5)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Sc	0.0106 (6)	0.0106 (6)	0.0050 (7)	0	0	0
K1	0.0313 (6)	0.0313 (6)	0.0142 (7)	0.0137 (3)	0	0
K2	0.0467 (6)	0.0467 (6)	0.0159 (7)	−0.0328 (4)	0	0
Si	0.0109 (6)	0.0109 (6)	0.0062 (6)	0.00103 (16)	−0.00025 (10)	−0.00025 (10)
O1	0.0286 (13)	0.0286 (13)	0.0140 (16)	−0.0173 (9)	0	0
O2	0.0343 (10)	0.0343 (10)	0.0031 (10)	−0.0152 (11)	0	0
F	0.0402 (17)	0.0261 (14)	0.0084 (17)	0.0008 (8)	0	0
O3	0.0420 (9)	0.0159 (8)	0.0265 (9)	0.0083 (5)	−0.0053 (6)	−0.0061 (4)

Bond lengths (Å)

Sc—F	2.0674 (1)	K1—O3^viii	2.8146 (14)
Sc—F^i	2.0674 (1)	K2—O1^ix	2.8156 (19)
Sc—O3^ii	2.0726 (14)	K2—O1^x	2.8156 (19)
Sc—O3^iii	2.0726 (14)	K2—O2	2.8811 (16)
Sc—O3^iv	2.0726 (14)	Si—O1	1.6421 (9)
Sc—O3^v	2.0726 (14)	Si—O2	1.6271 (5)
K1—O3^vi	2.8146 (14)	Si—O3	1.5846 (14)
K1—O3^iii	2.8146 (14)	Si—O3^v	1.5846 (14)
K1—O3^vii	2.8146 (14)

Symmetry codes: (i) −y+1/2, x−1/2, z+1/2; (ii) −x+1/2, y−1/2, −z+1/2; (iii) x+1/2, −y+1/2, −z+1/2; (iv) −y+1, −x, z; (v) y, x, z; (vi) y+1/2, −x+1/2, z−1/2; (vii) y+1/2, −x+1/2, −z+1/2; (viii) x+1/2, −y+1/2, z−1/2; (ix) −y+1/2, x+1/2, z−1/2; (x) −x+1/2, y+1/2, −z+1/2.

(III_223K)

Crystal data

FK2O6ScSi2	F(000) = 576
Mr = 294.3	Dx = 2.940 Mg m^−3
Tetragonal, P42/m21/n2/m†	Mo Kα radiation, λ = 0.7107 Å
q1 = 0.298600a* + 0.298600b*; q2 = -0.298600a* + 0.298600b*	Cell parameters from 4774 reflections
a = 8.9705 (4) Å	θ = 3.0–29.3°
c = 8.2615 (4) Å	µ = 2.73 mm^−1
V = 664.80 (5) Å^3	T = 293 K
Z = 4	0.46 × 0.41 × 0.31 mm

† Symmetry operations: (1) x₁, x₂, x₃, x₄, x₅; (2) −x₁, −x₂, x₃, −x₄, −x₅; (3) −x₂+1/2, x₁+1/2, x₃+1/2, −x₅+1/2, x₄+1/2; (4) x₂+1/2, −x₁+1/2, x₃+1/2, x₅+1/2, −x₄+1/2; (5) −x₁+1/2, x₂+1/2, −x₃+1/2, x₅, x₄; (6) x₁+1/2, −x₂+1/2, −x₃+1/2, −x₅, −x₄; (7) x₂, x₁, −x₃, x₄+1/2, −x₅+1/2; (8) −x₂, −x₁, −x₃, −x₄+1/2, x₅+1/2; (9) −x₁, −x₂, −x₃, −x₄, −x₅; (10) x₁, x₂, −x₃, x₄, x₅; (11) x₂+1/2, −x₁+1/2, −x₃+1/2, x₅+1/2, −x₄+1/2; (12) −x₂+1/2, x₁+1/2, −x₃+1/2, −x₅+1/2, x₄+1/2; (13) x₁+1/2, −x₂+1/2, x₃+1/2, −x₅, −x₄; (14) −x₁+1/2, x₂+1/2, x₃+1/2, x₅, x₄; (15) −x₂, −x₁, x₃, −x₄+1/2, x₅+1/2; (16) x₂, x₁, x₃, x₄+1/2, −x₅+1/2.

Data collection

Xcalibur, Ruby, Gemini ultra diffractometer	4131 independent reflections
Radiation source: Enhance (Mo) X-ray Source	1684 reflections with I > 3σ(I)
Graphite monochromator	Rint = 0.054
Detector resolution: 10.3575 pixels mm^-1	θmax = 29.4°, θmin = 3.0°
ω scans	h = −12→11
Absorption correction: analytical CrysAlisPro, Agilent Technologies, Version 1.171.36.20 (release 27-06-2012 CrysAlis171 .NET) (compiled Jul 11 2012,15:38:31) 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)	k = −10→12
Tmin = 0.406, Tmax = 0.552	l = −10→10
36339 measured reflections

Refinement

Refinement on F	0 constraints
R[F^2 > 2σ(F^2)] = 0.040	Weighting scheme based on measured s.u.'s w = 1/(σ^2(F) + 0.0001F^2)
wR(F^2) = 0.063	(Δ/σ)max = 0.037
S = 1.32	Δρmax = 1.69 e Å^−3
4131 reflections	Δρmin = −1.73 e Å^−3
187 parameters	Extinction correction: B-C type 1 Gaussian isotropic (Becker & Coppens, 1974)
0 restraints	Extinction coefficient: 8000 (200)

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
Sc	0.5	0	0.25	0.00436 (14)
K1	0.79288 (5)	0.20712 (5)	0	0.01446 (17)
K2	0.34291 (5)	0.34291 (5)	0	0.0234 (2)
Si	0.12243 (4)	0.12243 (4)	0.19662 (7)	0.00510 (15)
O1	0	0	0.2591 (3)	0.0103 (5)
O2	0.11661 (15)	0.11661 (15)	0	0.0127 (5)
F	0.5	0	0	0.0134 (5)
O3	0.07265 (12)	0.28124 (11)	0.25894 (14)	0.0121 (3)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Sc	0.00438 (19)	0.00438 (19)	0.0043 (3)	0	0	0
K1	0.0162 (2)	0.0162 (2)	0.0109 (4)	0.0061 (3)	0	0
K2	0.0288 (3)	0.0288 (3)	0.0125 (4)	−0.0191 (3)	0	0
Si	0.0052 (2)	0.0052 (2)	0.0049 (3)	0.00006 (19)	−0.00002 (15)	−0.00002 (15)
O1	0.0110 (7)	0.0110 (7)	0.0087 (12)	−0.0048 (8)	0	0
O2	0.0170 (7)	0.0170 (7)	0.0039 (12)	−0.0055 (8)	0	0
F	0.0199 (9)	0.0154 (9)	0.0048 (10)	−0.0019 (7)	0	0
O3	0.0144 (6)	0.0070 (5)	0.0148 (7)	0.0026 (4)	−0.0008 (5)	−0.0022 (4)

Bond lengths (Å)

	Average	Minimum	Maximum
Sc—F	2.0700 (14)	2.060 (3)	2.0820 (17)
Sc—F^i	2.0702 (14)	2.060 (3)	2.0820 (17)
Sc—O3^ii	2.078 (5)	2.054 (5)	2.100 (6)
Sc—O3^iii	2.078 (5)	2.054 (5)	2.100 (6)
Sc—O3^iv	2.078 (5)	2.054 (5)	2.100 (6)
Sc—O3^v	2.078 (5)	2.054 (5)	2.100 (6)
K1—O2^vi	3.026 (9)	2.879 (9)	3.218 (9)
K1—O2^vii	3.022 (9)	2.879 (9)	3.218 (9)
K1—O3^viii	2.808 (7)	2.708 (7)	2.941 (7)
K1—O3^iii	2.815 (7)	2.708 (7)	2.940 (7)
K1—O3^ix	2.808 (7)	2.708 (7)	2.941 (7)
K1—O3^x	2.815 (7)	2.708 (7)	2.940 (7)
K2—O1^xi	2.825 (5)	2.650 (6)	2.996 (5)
K2—O1^xii	2.825 (5)	2.650 (6)	2.996 (5)
K2—O2	2.888 (9)	2.802 (9)	2.952 (9)
K2—O3	3.280 (7)	2.832 (7)	3.716 (7)
K2—O3^xi	3.068 (7)	2.812 (7)	3.569 (7)
K2—O3^iii	3.087 (7)	2.812 (7)	3.569 (7)
K2—O3^xiii	3.295 (7)	2.832 (7)	3.716 (7)
K2—O3^xiv	3.280 (7)	2.832 (7)	3.716 (7)
K2—O3^xv	3.068 (7)	2.812 (7)	3.569 (7)
K2—O3^x	3.087 (7)	2.812 (7)	3.569 (7)
K2—O3^v	3.295 (7)	2.832 (7)	3.716 (7)
Si—O1	1.647 (4)	1.630 (4)	1.664 (4)
Si—O2	1.632 (2)	1.622 (3)	1.641 (2)
Si—O3	1.590 (6)	1.572 (6)	1.608 (6)
Si—O3^v	1.590 (6)	1.572 (6)	1.608 (6)

Symmetry codes: (i) −x₂+1/2, x₁−1/2, x₃+1/2, −x₅+1/2, x₄+1/2; (ii) −x₁+1/2, x₂−1/2, −x₃+1/2, x₅, x₄; (iii) x₁+1/2, −x₂+1/2, −x₃+1/2, −x₅, −x₄; (iv) −x₂+1, −x₁, x₃, −x₄+1/2, x₅+1/2; (v) x₂, x₁, x₃, x₄+1/2, −x₅+1/2; (vi) x₁+1, x₂, x₃, x₄, x₅; (vii) −x₁+1, −x₂, x₃, −x₄, −x₅; (viii) x₂+1/2, −x₁+1/2, x₃−1/2, x₅+1/2, −x₄+1/2; (ix) x₂+1/2, −x₁+1/2, −x₃+1/2, x₅+1/2, −x₄+1/2; (x) x₁+1/2, −x₂+1/2, x₃−1/2, −x₅, −x₄; (xi) −x₂+1/2, x₁+1/2, x₃−1/2, −x₅+1/2, x₄+1/2; (xii) −x₁+1/2, x₂+1/2, −x₃+1/2, x₅, x₄; (xiii) x₂, x₁, −x₃, x₄+1/2, −x₅+1/2; (xiv) x₁, x₂, −x₃, x₄, x₅; (xv) −x₂+1/2, x₁+1/2, −x₃+1/2, −x₅+1/2, x₄+1/2.

(III_173K)

Crystal data

FK2O6ScSi2	F(000) = 576
Mr = 294.3	Dx = 2.942 Mg m^−3
Tetragonal, P42/m21/n2/m†	Mo Kα radiation, λ = 0.71073 Å
q1 = 0.298700a* + 0.298700b*; q2 = -0.298700a* + 0.298700b*	Cell parameters from 5195 reflections
a = 8.9622 (4) Å	θ = 3–29.3°
c = 8.2705 (4) Å	µ = 2.72 mm^−1
V = 664.30 (5) Å^3	T = 293 K
Z = 4	0.45 × 0.37 × 0.21 mm

† Symmetry operations: (1) x₁, x₂, x₃, x₄, x₅; (2) −x₁, −x₂, x₃, −x₄, −x₅; (3) −x₂+1/2, x₁+1/2, x₃+1/2, −x₅+1/2, x₄+1/2; (4) x₂+1/2, −x₁+1/2, x₃+1/2, x₅+1/2, −x₄+1/2; (5) −x₁+1/2, x₂+1/2, −x₃+1/2, x₅, x₄; (6) x₁+1/2, −x₂+1/2, −x₃+1/2, −x₅, −x₄; (7) x₂, x₁, −x₃, x₄+1/2, −x₅+1/2; (8) −x₂, −x₁, −x₃, −x₄+1/2, x₅+1/2; (9) −x₁, −x₂, −x₃, −x₄, −x₅; (10) x₁, x₂, −x₃, x₄, x₅; (11) x₂+1/2, −x₁+1/2, −x₃+1/2, x₅+1/2, −x₄+1/2; (12) −x₂+1/2, x₁+1/2, −x₃+1/2, −x₅+1/2, x₄+1/2; (13) x₁+1/2, −x₂+1/2, x₃+1/2, −x₅, −x₄; (14) −x₁+1/2, x₂+1/2, x₃+1/2, x₅, x₄; (15) −x₂, −x₁, x₃, −x₄+1/2, x₅+1/2; (16) x₂, x₁, x₃, x₄+1/2, −x₅+1/2.

Data collection

Xcalibur, Ruby, Gemini ultra diffractometer	3986 independent reflections
Radiation source: Enhance (Mo) X-ray Source	2178 reflections with I > 3σ(I)
Graphite monochromator	Rint = 0.056
Detector resolution: 10.3575 pixels mm^-1	θmax = 29.4°, θmin = 3.0°
ω scans	h = −11→12
Absorption correction: analytical CrysAlisPro, Agilent Technologies, Version 1.171.36.20 (release 27-06-2012 CrysAlis171 .NET) (compiled Jul 11 2012,15:38:31) 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)	k = −12→12
Tmin = 0.443, Tmax = 0.676	l = −11→9
38281 measured reflections

Refinement

Refinement on F	0 constraints
R[F^2 > 2σ(F^2)] = 0.050	Weighting scheme based on measured s.u.'s w = 1/(σ^2(F) + 0.0001F^2)
wR(F^2) = 0.067	(Δ/σ)max = 0.034
S = 1.82	Δρmax = 2.77 e Å^−3
3986 reflections	Δρmin = −3.32 e Å^−3
187 parameters	Extinction correction: B-C type 1 Gaussian isotropic (Becker & Coppens, 1974)
0 restraints	Extinction coefficient: 9100 (400)

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
Sc	0.5	0	0.25	0.00357 (15)
K1	0.79283 (5)	0.20717 (5)	0	0.01151 (17)
K2	0.34303 (5)	0.34303 (5)	0	0.0179 (2)
Si	0.12251 (4)	0.12251 (4)	0.19664 (7)	0.00440 (15)
O1	0	0	0.2586 (3)	0.0082 (5)
O2	0.11637 (16)	0.11637 (16)	0	0.0111 (5)
F	0.5	0	0	0.0107 (5)
O3	0.07260 (12)	0.28133 (11)	0.25896 (14)	0.0099 (3)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Sc	0.0030 (2)	0.0030 (2)	0.0047 (3)	0	0	0
K1	0.0123 (3)	0.0123 (3)	0.0100 (4)	0.0045 (3)	0	0
K2	0.0214 (3)	0.0214 (3)	0.0110 (4)	−0.0137 (3)	0	0
Si	0.0040 (2)	0.0040 (2)	0.0051 (3)	−0.0001 (2)	−0.00002 (15)	−0.00002 (15)
O1	0.0081 (7)	0.0081 (7)	0.0085 (12)	−0.0034 (8)	0	0
O2	0.0140 (7)	0.0140 (7)	0.0052 (12)	−0.0033 (9)	0	0
F	0.0143 (9)	0.0114 (9)	0.0063 (10)	−0.0021 (7)	0	0
O3	0.0103 (5)	0.0054 (5)	0.0139 (7)	0.0018 (4)	−0.0006 (5)	−0.0017 (4)

Bond lengths (Å)

	Average	Minimum	Maximum
Sc—F	2.0737 (13)	2.062 (2)	2.0868 (15)
Sc—F^i	2.0739 (13)	2.062 (2)	2.0868 (15)
Sc—O3^ii	2.078 (5)	2.051 (5)	2.104 (5)
Sc—O3^iii	2.077 (5)	2.051 (5)	2.104 (5)
Sc—O3^iv	2.078 (5)	2.051 (5)	2.104 (5)
Sc—O3^v	2.077 (5)	2.051 (5)	2.104 (5)
K1—O2^vi	3.025 (8)	2.863 (8)	3.250 (8)
K1—O2^vii	3.021 (8)	2.863 (8)	3.250 (8)
K1—O3^viii	2.809 (7)	2.701 (7)	2.951 (7)
K1—O3^iii	2.817 (7)	2.701 (7)	2.951 (7)
K1—O3^ix	2.809 (7)	2.701 (7)	2.951 (7)
K1—O3^x	2.817 (7)	2.701 (7)	2.951 (7)
K2—O1^xi	2.830 (4)	2.641 (5)	3.011 (5)
K2—O1^xii	2.830 (4)	2.641 (5)	3.011 (5)
K2—O2	2.897 (9)	2.800 (9)	2.958 (9)
K2—O3	3.282 (7)	2.772 (7)	3.766 (7)
K2—O3^xi	3.067 (7)	2.787 (7)	3.676 (6)
K2—O3^iii	3.090 (7)	2.787 (7)	3.676 (6)
K2—O3^xiii	3.299 (7)	2.772 (7)	3.766 (7)
K2—O3^xiv	3.282 (7)	2.772 (7)	3.766 (7)
K2—O3^xv	3.067 (7)	2.787 (7)	3.676 (6)
K2—O3^x	3.090 (7)	2.787 (7)	3.676 (6)
K2—O3^v	3.299 (7)	2.772 (7)	3.766 (7)
Si—O1	1.648 (4)	1.630 (6)	1.668 (5)
Si—O2	1.636 (2)	1.624 (2)	1.648 (2)
Si—O3	1.591 (6)	1.574 (6)	1.610 (6)
Si—O3^v	1.592 (6)	1.574 (6)	1.610 (6)

Symmetry codes: (i) −x₂+1/2, x₁−1/2, x₃+1/2, −x₅+1/2, x₄+1/2; (ii) −x₁+1/2, x₂−1/2, −x₃+1/2, x₅, x₄; (iii) x₁+1/2, −x₂+1/2, −x₃+1/2, −x₅, −x₄; (iv) −x₂+1, −x₁, x₃, −x₄+1/2, x₅+1/2; (v) x₂, x₁, x₃, x₄+1/2, −x₅+1/2; (vi) x₁+1, x₂, x₃, x₄, x₅; (vii) −x₁+1, −x₂, x₃, −x₄, −x₅; (viii) x₂+1/2, −x₁+1/2, x₃−1/2, x₅+1/2, −x₄+1/2; (ix) x₂+1/2, −x₁+1/2, −x₃+1/2, x₅+1/2, −x₄+1/2; (x) x₁+1/2, −x₂+1/2, x₃−1/2, −x₅, −x₄; (xi) −x₂+1/2, x₁+1/2, x₃−1/2, −x₅+1/2, x₄+1/2; (xii) −x₁+1/2, x₂+1/2, −x₃+1/2, x₅, x₄; (xiii) x₂, x₁, −x₃, x₄+1/2, −x₅+1/2; (xiv) x₁, x₂, −x₃, x₄, x₅; (xv) −x₂+1/2, x₁+1/2, −x₃+1/2, −x₅+1/2, x₄+1/2.