Structure and complex twinning of dysprosium disilicate (Dy2Si2O7), Type B

Fleet, M.E.; Liu, X.

doi:10.1107/S0108768100008545

Structure and complex twinning of dysprosium disilicate (Dy₂Si₂O₇), Type B

Dysprosium disilicate (Dy₂Si₂O₇) is triclinic with a = 6.6158 (2), b = 6.6604 (2), c = 12.0551 (4) Å, α = 94.373 (2), β = 90.836 (2), γ = 91.512 (2)°, V = 529.4 (1) Å³, space group P $\overline 1$ , Z = 4 and D_x = 6.156 g cm⁻³. The structure (single-crystal X-ray, R = 0.033, wR = 0.041) is built from a linear triple tetrahedral group [Si₃O₁₀] and isolated [SiO₄] tetrahedron cross-linked by Dy³⁺ in one sixfold and three eightfold coordinated positions, and corresponds to the presently revised type B structure of Ho₂Si₂O₇. The formation of the unusual linear triple tetrahedral group in the type B structure allows for a more continuous transition in the mean size of REE³⁺O_n (REE = rare earth element) polyhedra in REE disilicates through the 4f transition metal series. The crystal of Dy₂Si₂O₇ investigated was complexly twinned such that the diffraction pattern was also consistent with a larger dimensionally monoclinic unit cell (a = 22.5354, b = 14.2102, c = 6.6158 Å, β = 91.788°), which resulted in an apparent superstructure of the type B structure in space group C1. Lattice coincidence with the type B unit cell appears to have been maintained during crystal synthesis and quenching by the complex sector-zoned growth twin.

Keywords: Twinning; Dysprosium disilicate.

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Supporting information

	Crystallographic Information File (CIF) https://doi.org/10.1107/S0108768100008545/br0099sup1.cif Contains datablocks global, I
	Structure factor file (CIF format) https://doi.org/10.1107/S0108768100008545/br0099sup2.hkl Supplementary material

Computing details top

Data collection: COLLECT (Nonius, 1997); cell refinement: COLLECT (Nonius, 1997); data reduction: SUNY Buffalo DATAP77; program(s) used to solve structure: SHELXTL PC Siemens; program(s) used to refine structure: SUNY Buffalo LINEX77; molecular graphics: Shape Software ATOMS, ORTEP-3 for Windows.

dysprosium disilicate top

Crystal data top

Dy₂Si₂O₇	Z = 4
M_r = 493.17	D_x = 6.156 Mg m⁻³
Triclinic, P1	Mo Kα radiation, λ = 0.70926 Å
a = 6.6158 (2) Å	Cell parameters from 32768 reflections
b = 6.6604 (2) Å	θ = 2–35°
c = 12.0551 (4) Å	µ = 28.45 mm⁻¹
α = 94.373 (2)°	T = 293 K
β = 90.836 (2)°	Prism, colorless
γ = 91.512 (2)°	0.11 × 0.10 × 0.05 mm
V = 529.39 Å³

Data collection top

Nonius KappaCCD diffractometer	4470 independent reflections
Radiation source: fine-focus sealed tube	3220 reflections with I ≥ 3σ(I)
Graphite monochromator	R_int = 0.107
area detector and scans	θ_max = 35°, θ_min = 2°
Absorption correction: gaussian (Coppens, Leiserowitz & Rabinovich, 1965)	h = −10→10
T_min = 0.144, T_max = 0.380	k = −5→9
32768 measured reflections	l = 0→19

Refinement top

Refinement on F	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F² > 2σ(F²)] = 0.033	w = 1/[σ(F)² + (0.025F)²], except w = 0 if I < 3σ(I)
wR(F²) = 0.041	(Δ/σ)_max = 0.001
S = 0.98	Δρ_max = 4.65 e Å⁻³
4470 reflections	Δρ_min = −4.70 e Å⁻³
204 parameters	Extinction correction: B-C type 1 Lorentzian isotropic, Coppens & Hamilton (1970)
0 restraints	Extinction coefficient: 0.31 (2)

Crystal data top

Dy₂Si₂O₇	γ = 91.512 (2)°
M_r = 493.17	V = 529.39 Å³
Triclinic, P1	Z = 4
a = 6.6158 (2) Å	Mo Kα radiation
b = 6.6604 (2) Å	µ = 28.45 mm⁻¹
c = 12.0551 (4) Å	T = 293 K
α = 94.373 (2)°	0.11 × 0.10 × 0.05 mm
β = 90.836 (2)°

Data collection top

Nonius KappaCCD diffractometer	4470 independent reflections
Absorption correction: gaussian (Coppens, Leiserowitz & Rabinovich, 1965)	3220 reflections with I ≥ 3σ(I)
T_min = 0.144, T_max = 0.380	R_int = 0.107
32768 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.033	204 parameters
wR(F²) = 0.041	0 restraints
S = 0.98	Δρ_max = 4.65 e Å⁻³
4470 reflections	Δρ_min = −4.70 e Å⁻³

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
Dy(1)	0.94853 (4)	0.33132 (4)	0.11643 (2)	0.00588 (9)
Dy(2)	0.88556 (4)	0.09387 (4)	0.35971 (2)	0.00579 (9)
Dy(3)	0.37254 (4)	0.78116 (4)	0.36895 (2)	0.00749 (9)
Dy(4)	0.66787 (4)	0.82973 (4)	0.10747 (2)	0.00742 (9)
Si(1)	0.1553 (2)	0.8528 (2)	0.1164 (1)	0.0048 (3)
Si(2)	0.4873 (3)	0.3370 (2)	0.1759 (1)	0.0061 (3)
Si(3)	0.3777 (3)	0.2743 (2)	0.4048 (1)	0.0064 (3)
Si(4)	0.1433 (3)	0.3702 (2)	0.6180 (1)	0.0056 (3)
O(1)	0.6418 (6)	0.4938 (6)	0.1256 (3)	0.0076 (7)
O(2)	0.6179 (7)	0.1419 (6)	0.2095 (4)	0.0120 (8)
O(3)	0.2978 (7)	0.2990 (7)	0.0947 (3)	0.0097 (8)
O(4)	0.4055 (6)	0.4283 (6)	0.3065 (3)	0.0072 (7)
O(5)	0.5836 (7)	0.1702 (6)	0.4454 (4)	0.0090 (8)
O(6)	0.2276 (6)	0.0965 (6)	0.3755 (4)	0.0100 (8)
O(7)	0.2885 (7)	0.4229 (6)	0.5118 (3)	0.0093 (8)
O(8)	0.2841 (7)	0.2167 (7)	0.6875 (4)	0.0118 (8)
O(9)	0.9629 (7)	0.2255 (6)	0.5700 (4)	0.0113 (8)
O(10)	0.0732 (7)	0.5777 (6)	0.6854 (4)	0.0109 (8)
O(11)	0.2411 (7)	0.9129 (7)	0.9994 (3)	0.0111 (8)
O(12)	0.3462 (6)	0.7886 (7)	0.1888 (4)	0.0095 (8)
O(13)	0.9982 (6)	0.6683 (6)	0.0809 (3)	0.0077 (8)
O(14)	0.0029 (6)	0.0165 (6)	0.1830 (3)	0.0075 (7)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Dy(1)	0.0081 (1)	0.0071 (1)	0.0026 (1)	−0.00055 (9)	0.00044 (9)	0.00098 (9)
Dy(2)	0.0061 (1)	0.0076 (1)	0.0037 (1)	−0.00091 (9)	0.00145 (9)	0.00084 (9)
Dy(3)	0.0078 (1)	0.0126 (1)	0.0020 (1)	0.0012 (1)	0.00071 (9)	−0.00059 (9)
Dy(4)	0.0100 (1)	0.0072 (1)	0.0054 (1)	0.00030 (9)	0.00416 (9)	0.00193 (9)
Si(1)	0.0049 (7)	0.0072 (7)	0.0024 (6)	−0.0016 (5)	0.0017 (5)	0.0014 (5)
Si(2)	0.0075 (7)	0.0070 (7)	0.0039 (7)	−0.0010 (5)	0.0007 (5)	0.0026 (5)
Si(3)	0.0073 (7)	0.0070 (7)	0.0050 (7)	−0.0016 (5)	0.0001 (5)	0.0016 (5)
Si(4)	0.0060 (7)	0.0044 (6)	0.0063 (7)	−0.0014 (5)	0.0001 (5)	0.0005 (5)
O(1)	0.006 (2)	0.011 (2)	0.005 (2)	0.003 (1)	0.001 (1)	0.001 (1)
O(2)	0.019 (2)	0.007 (2)	0.010 (2)	0.003 (2)	−0.002 (2)	0.002 (1)
O(3)	0.009 (2)	0.019 (2)	0.002 (2)	−0.002 (2)	−0.001 (1)	0.002 (1)
O(4)	0.011 (2)	0.010 (2)	0.001 (2)	−0.004 (1)	0.000 (1)	0.003 (1)
O(5)	0.008 (2)	0.014 (2)	0.005 (2)	−0.004 (1)	0.001 (1)	0.004 (1)
O(6)	0.005 (2)	0.010 (2)	0.014 (2)	0.002 (1)	−0.002 (2)	−0.006 (2)
O(7)	0.013 (2)	0.010 (2)	0.005 (2)	−0.002 (2)	0.006 (1)	−0.004 (1)
O(8)	0.006 (2)	0.016 (2)	0.015 (2)	0.003 (2)	0.000 (2)	0.004 (2)
O(9)	0.014 (2)	0.011 (2)	0.008 (2)	−0.006 (2)	−0.004 (2)	0.001 (1)
O(10)	0.017 (2)	0.010 (2)	0.006 (2)	0.005 (2)	−0.001 (2)	0.000 (1)
O(11)	0.019 (2)	0.010 (2)	0.003 (2)	−0.008 (2)	0.006 (2)	−0.003 (1)
O(12)	0.006 (2)	0.016 (2)	0.007 (2)	−0.004 (2)	0.000 (1)	0.000 (1)
O(13)	0.006 (2)	0.008 (2)	0.008 (2)	−0.006 (1)	0.001 (1)	−0.003 (1)
O(14)	0.008 (2)	0.006 (2)	0.008 (2)	−0.002 (1)	−0.001 (1)	0.001 (1)

Geometric parameters (Å, º) top

Dy(1)—O(1)	2.325 (2)	Dy(4)—O(2)^vi	2.367 (4)
Dy(1)—O(2)	2.789 (3)	Dy(4)—O(3)^vii	2.537 (4)
Dy(1)—O(3)ⁱ	2.343 (1)	Dy(4)—O(8)ⁱⁱ	2.531 (5)
Dy(1)—O(10)ⁱⁱ	2.427 (4)	Dy(4)—O(11)^viii	2.295 (4)
Dy(1)—O(11)ⁱⁱ	2.380 (3)	Dy(4)—O(12)	2.374 (2)
Dy(1)—O(13)	2.333 (4)	Dy(4)—O(13)	2.475 (2)
Dy(1)—O(13)ⁱⁱⁱ	2.410 (4)	Dy(4)—O(14)^ix	2.629 (2)
Dy(1)—O(14)ⁱ	2.336 (4)	Si(1)—O(11)^x	1.602 (4)
Dy(2)—O(2)	2.558 (3)	Si(1)—O(12)	1.610 (3)
Dy(2)—O(5)	2.313 (2)	Si(1)—O(13)^xi	1.616 (3)
Dy(2)—O(6)ⁱ	2.267 (4)	Si(1)—O(14)^vi	1.673 (3)
Dy(2)—O(8)^iv	2.354 (4)	Si(2)—O(1)	1.600 (4)
Dy(2)—O(9)	2.656 (4)	Si(2)—O(2)	1.652 (4)
Dy(2)—O(9)^v	2.571 (4)	Si(2)—O(3)	1.582 (3)
Dy(2)—O(10)ⁱⁱ	2.304 (4)	Si(2)—O(4)	1.744 (4)
Dy(2)—O(14)ⁱ	2.304 (4)	Si(3)—O(4)	1.635 (4)
Dy(3)—O(4)	2.429 (4)	Si(3)—O(5)	1.630 (3)
Dy(3)—O(5)ⁱⁱ	2.250 (4)	Si(3)—O(6)	1.542 (3)
Dy(3)—O(6)^vi	2.328 (4)	Si(3)—O(7)	1.688 (4)
Dy(3)—O(8)ⁱⁱ	2.381 (1)	Si(4)—O(7)	1.665 (4)
Dy(3)—O(9)ⁱⁱ	2.348 (1)	Si(4)—O(8)	1.665 (4)
Dy(3)—O(12)	2.181 (4)	Si(4)—O(9)^xi	1.588 (3)
Dy(4)—O(1)	2.267 (4)	Si(4)—O(10)	1.630 (4)

O(11)^x—Si(1)—O(12)	106.8 (3)	O(4)—Si(3)—O(6)	114.4 (2)
O(11)^x—Si(1)—O(13)^xi	103.1 (2)	O(4)—Si(3)—O(7)	103.3 (2)
O(11)^x—Si(1)—O(14)^vi	116.8 (2)	O(5)—Si(3)—O(6)	104.8 (2)
O(12)—Si(1)—O(13)^xi	113.6 (2)	O(5)—Si(3)—O(7)	109.0 (2)
O(12)—Si(1)—O(14)^vi	114.9 (2)	O(6)—Si(3)—O(7)	109.7 (2)
O(13)^xi—Si(1)—O(14)^vi	101.1 (2)	O(7)—Si(4)—O(8)	103.2 (2)
O(1)—Si(2)—O(2)	107.6 (2)	O(7)—Si(4)—O(9)^xi	107.6 (2)
O(1)—Si(2)—O(3)	109.4 (2)	O(7)—Si(4)—O(10)	110.2 (2)
O(1)—Si(2)—O(4)	111.0 (2)	O(8)—Si(4)—O(9)^xi	102.7 (2)
O(2)—Si(2)—O(3)	118.8 (3)	O(8)—Si(4)—O(10)	117.2 (2)
O(2)—Si(2)—O(4)	100.6 (2)	O(9)^xi—Si(4)—O(10)	114.8 (3)
O(3)—Si(2)—O(4)	109.1 (2)	Si(2)—O(4)—Si(3)	119.7 (3)
O(4)—Si(3)—O(5)	115.7 (2)	Si(3)—O(7)—Si(4)	131.4 (3)

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

Experimental details

Crystal data
Chemical formula	Dy₂Si₂O₇
M_r	493.17
Crystal system, space group	Triclinic, P1
Temperature (K)	293
a, b, c (Å)	6.6158 (2), 6.6604 (2), 12.0551 (4)
α, β, γ (°)	94.373 (2), 90.836 (2), 91.512 (2)
V (Å³)	529.39
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	28.45
Crystal size (mm)	0.11 × 0.10 × 0.05

Data collection
Diffractometer	Nonius KappaCCD diffractometer
Absorption correction	Gaussian (Coppens, Leiserowitz & Rabinovich, 1965)
T_min, T_max	0.144, 0.380
No. of measured, independent and observed [I ≥ 3σ(I)] reflections	32768, 4470, 3220
R_int	0.107
(sin θ/λ)_max (Å⁻¹)	0.809

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.033, 0.041, 0.98
No. of reflections	4470
No. of parameters	204
Δρ_max, Δρ_min (e Å⁻³)	4.65, −4.70

Computer programs: COLLECT (Nonius, 1997), SUNY Buffalo DATAP77, SHELXTL PC Siemens, SUNY Buffalo LINEX77, Shape Software ATOMS, ORTEP-3 for Windows.

Selected geometric parameters (Å, º) top

Dy(1)—O(1)	2.325 (2)	Dy(2)—O(14)ⁱ	2.304 (4)
Dy(1)—O(2)	2.789 (3)	Dy(3)—O(4)	2.429 (4)
Dy(1)—O(3)ⁱ	2.343 (1)	Dy(3)—O(5)ⁱⁱ	2.250 (4)
Dy(1)—O(10)ⁱⁱ	2.427 (4)	Dy(3)—O(6)^vi	2.328 (4)
Dy(1)—O(11)ⁱⁱ	2.380 (3)	Dy(3)—O(8)ⁱⁱ	2.381 (1)
Dy(1)—O(13)	2.333 (4)	Dy(3)—O(9)ⁱⁱ	2.348 (1)
Dy(1)—O(13)ⁱⁱⁱ	2.410 (4)	Dy(3)—O(12)	2.181 (4)
Dy(1)—O(14)ⁱ	2.336 (4)	Dy(4)—O(1)	2.267 (4)
Dy(2)—O(2)	2.558 (3)	Dy(4)—O(2)^vi	2.367 (4)
Dy(2)—O(5)	2.313 (2)	Dy(4)—O(3)^vii	2.537 (4)
Dy(2)—O(6)ⁱ	2.267 (4)	Dy(4)—O(8)ⁱⁱ	2.531 (5)
Dy(2)—O(8)^iv	2.354 (4)	Dy(4)—O(11)^viii	2.295 (4)
Dy(2)—O(9)	2.656 (4)	Dy(4)—O(12)	2.374 (2)
Dy(2)—O(9)^v	2.571 (4)	Dy(4)—O(13)	2.475 (2)
Dy(2)—O(10)ⁱⁱ	2.304 (4)	Dy(4)—O(14)^ix	2.629 (2)

O(11)^x—Si(1)—O(12)	106.8 (3)	O(4)—Si(3)—O(6)	114.4 (2)
O(11)^x—Si(1)—O(13)^xi	103.1 (2)	O(4)—Si(3)—O(7)	103.3 (2)
O(11)^x—Si(1)—O(14)^vi	116.8 (2)	O(5)—Si(3)—O(6)	104.8 (2)
O(12)—Si(1)—O(13)^xi	113.6 (2)	O(5)—Si(3)—O(7)	109.0 (2)
O(12)—Si(1)—O(14)^vi	114.9 (2)	O(6)—Si(3)—O(7)	109.7 (2)
O(13)^xi—Si(1)—O(14)^vi	101.1 (2)	O(7)—Si(4)—O(8)	103.2 (2)
O(1)—Si(2)—O(2)	107.6 (2)	O(7)—Si(4)—O(9)^xi	107.6 (2)
O(1)—Si(2)—O(3)	109.4 (2)	O(7)—Si(4)—O(10)	110.2 (2)
O(1)—Si(2)—O(4)	111.0 (2)	O(8)—Si(4)—O(9)^xi	102.7 (2)
O(2)—Si(2)—O(3)	118.8 (3)	O(8)—Si(4)—O(10)	117.2 (2)
O(2)—Si(2)—O(4)	100.6 (2)	O(9)^xi—Si(4)—O(10)	114.8 (3)
O(3)—Si(2)—O(4)	109.1 (2)	Si(2)—O(4)—Si(3)	119.7 (3)
O(4)—Si(3)—O(5)	115.7 (2)	Si(3)—O(7)—Si(4)	131.4 (3)

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