The crystal structure of new quantum memory-storage material Sc1.368Y0.632SiO5

Iskhakova, L.D.; Ilyukhin, A.B.; Kutovoi, S.A.; Vlasov, V.I.; Zavartsev, Y.D.; Tarasov, V.F.; Eremina, R.M.

doi:10.1107/S2053229619010507

The crystal structure of new quantum memory-storage material Sc_1.368Y_0.632SiO₅

L. D. Iskhakova, A. B. Ilyukhin, S. A. Kutovoi, V. I. Vlasov, Y. D. Zavartsev, V. F. Tarasov and R. M. Eremina

Monoisotopic scandium yttrium oxyorthosilicate crystals as a material for quantum memory storage with high optical quality were grown by the Czochralski method. This material, of composition Sc_1.368Y_0.632SiO₅, is characterized by congruent melting and a melting point 60 K below the temperature for the ideal solid-solution series Y₂SiO₅–Sc₂SiO₅. The structure of the crystals was refined on the basis of high-quality single-crystal X-ray diffraction data. Sc_1.368Y_0.632SiO₅ belongs to B-type RE₂SiO₅ (space group C2/c). Scandium and yttrium cations are distributed among two 8f sites with coordination numbers 7 and 6 for which the occupancy parameters ratios Sc:Y and average bond lengths are, respectively, 0.473:0.527 and RE1—O = 2.305 (2) Å, and 0.895:0.105 and RE2—O = 2.143 (2) Å. It is shown that the character of the occupancy of the positions of the cations with coordination numbers (CN) 6 and 7 for these solid solutions can be approximated by a polynomial dependence, the magnitude of the coefficients of which depends on the difference in the ionic radii of the cations. A preliminary electron paramagnetic resonance (EPR) study shows that activator ions with a large ionic radius at a concentration less than 0.1% occupy a position with CN = 7.

Keywords: scandium yttrium oxyorthosilicate; physicochemical properties; crystal structure; EPR spectroscopy; quantum memory-storage material.

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Supporting information

	Crystallographic Information File (CIF) https://doi.org/10.1107/S2053229619010507/sk3731sup1.cif Contains datablocks global, I
	Structure factor file (CIF format) https://doi.org/10.1107/S2053229619010507/sk3731Isup2.hkl Contains datablock I

CCDC reference: 1942657

Computing details top

Data collection: APEX3 (Bruker, 2018); cell refinement: SAINT (Bruker, 2018); data reduction: SAINT (Bruker, 2018); program(s) used to solve structure: SHELXT (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2018 (Sheldrick, 2015b); molecular graphics: SHELXTL (Bruker, 2018); software used to prepare material for publication: SHELXTL (Bruker, 2018).

Scandium yttrium oxyorthosilicate top

Crystal data top

Sc_1.368Y_0.632SiO₅	F(000) = 859
M_r = 225.75	D_x = 3.868 Mg m⁻³
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2yc	Cell parameters from 5866 reflections
a = 13.9162 (5) Å	θ = 3.0–39.5°
b = 6.5030 (2) Å	µ = 12.00 mm⁻¹
c = 10.0733 (4) Å	T = 150 K
β = 121.721 (1)°	Irregular, colourless
V = 775.43 (5) Å³	0.4 × 0.4 × 0.2 mm
Z = 8

Data collection top

Bruker APEX3 CCD diffractometer	2076 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.062
φ and ω scans	θ_max = 39.5°, θ_min = 3.4°
Absorption correction: multi-scan (SADABS; Krause et al., 2015)	h = −24→24
T_min = 0.061, T_max = 0.279	k = −11→11
9302 measured reflections	l = −18→17
2239 independent reflections

Refinement top

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)] = 0.041	w = 1/[σ²(F_o²) + (0.080P)² + 1.P] where P = (F_o² + 2F_c²)/3
wR(F²) = 0.111	(Δ/σ)_max = 0.001
S = 0.98	Δρ_max = 2.01 e Å⁻³
2239 reflections	Δρ_min = −2.09 e Å⁻³
76 parameters	Extinction correction: SHELXL2018 (Sheldrick, 2015b), Fc^*=kFc[1+0.001xFc²λ³/sin(2θ)]^-1/4
0 restraints	Extinction coefficient: 0.062 (3)

Special details top

Experimental. The following wavelength and cell were deduced by SADABS from the direction cosines etc. They are given here for emergency use only: CELL 0.71079 13.936 6.510 10.089 90.016 121.730 90.037

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. The XRD experimental data were collected on a Bruker SMART APEX3 diffractometer (graphite monochromator, CCD detector, Mo Kα radiation, λ = 0.71073 Å, T = 150 K). Analysis of the reflection conditions confirmed the space group as C2/c, Z = 8. An absorption correction was done using the multi-scan method SADABS (Krause et al., 2015). The structure for Lu₂SiO₅ (Gustafsson et al., 2001) was used for the initial structure solution. All calculations were performed using the SHELXS and SHELXL programs (Sheldrick, 2015). The crystallographic data and refinement parameters are presented in Table 1. It should be noted that attempts to refine the Y and Sc atoms without equal site (EXYZ) constraints resulted in unrealistic atomic displacement parameters.

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

	x	y	z	U_iso*/U_eq	Occ. (<1)
Y1	0.54003 (2)	0.74582 (3)	0.47192 (3)	0.00629 (10)	0.527 (6)
Sc1	0.54003 (2)	0.74582 (3)	0.47192 (3)	0.00629 (10)	0.473 (6)
Y2	0.35953 (3)	0.62123 (5)	0.65961 (3)	0.00489 (11)	0.105 (4)
Sc2	0.35953 (3)	0.62123 (5)	0.65961 (3)	0.00489 (11)	0.895 (4)
Si1	0.31652 (4)	0.09224 (8)	0.69201 (6)	0.00455 (14)
O1	0.41423 (14)	0.0143 (3)	0.86269 (19)	0.0156 (3)
O2	0.37268 (15)	0.2941 (3)	0.6622 (2)	0.0141 (3)
O3	0.20114 (13)	0.1458 (2)	0.68586 (18)	0.0088 (3)
O4	0.29676 (14)	−0.0798 (2)	0.56393 (18)	0.0102 (3)
O5	0.48321 (12)	0.5961 (2)	0.60705 (17)	0.0070 (2)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Y1	0.00721 (14)	0.00781 (14)	0.00637 (14)	−0.00038 (6)	0.00531 (10)	−0.00201 (6)
Sc1	0.00721 (14)	0.00781 (14)	0.00637 (14)	−0.00038 (6)	0.00531 (10)	−0.00201 (6)
Y2	0.00639 (15)	0.00717 (15)	0.00306 (14)	0.00008 (8)	0.00383 (11)	0.00083 (8)
Sc2	0.00639 (15)	0.00717 (15)	0.00306 (14)	0.00008 (8)	0.00383 (11)	0.00083 (8)
Si1	0.0061 (2)	0.0053 (2)	0.0032 (2)	0.00027 (14)	0.00305 (17)	0.00030 (14)
O1	0.0107 (6)	0.0269 (8)	0.0069 (6)	0.0076 (6)	0.0031 (5)	0.0067 (5)
O2	0.0135 (6)	0.0088 (6)	0.0249 (9)	−0.0036 (5)	0.0135 (6)	0.0012 (6)
O3	0.0075 (5)	0.0130 (6)	0.0085 (6)	0.0013 (4)	0.0059 (5)	0.0010 (4)
O4	0.0129 (6)	0.0100 (5)	0.0079 (5)	−0.0002 (5)	0.0058 (5)	−0.0038 (4)
O5	0.0085 (5)	0.0100 (5)	0.0056 (5)	−0.0001 (4)	0.0058 (4)	0.0013 (4)

Geometric parameters (Å, º) top

Y1—O5	2.1349 (14)	Y2—O3^vi	2.1316 (15)
Y1—O1ⁱ	2.1641 (19)	Y2—O2	2.1341 (18)
Y1—O3ⁱⁱ	2.2391 (15)	Y2—O4^vii	2.1415 (17)
Y1—O2ⁱⁱⁱ	2.2571 (18)	Y2—O4^viii	2.1733 (16)
Y1—O1^iv	2.2614 (18)	Y2—O5^v	2.2208 (15)
Y1—O5ⁱⁱⁱ	2.3262 (15)	Y2—Si1^vii	3.1705 (6)
Y1—O2ⁱ	2.754 (2)	Y2—Y2^v	3.3339 (6)
Y1—Si1ⁱ	3.0840 (6)	Y2—Si1^viii	3.3690 (6)
Y1—Y2^v	3.3063 (4)	Y2—Y2^ix	3.4828 (6)
Y1—Si1ⁱⁱⁱ	3.3597 (6)	Si1—O3	1.6120 (16)
Y1—Y2ⁱⁱⁱ	3.3695 (4)	Si1—O1	1.6136 (16)
Y1—Si1ⁱⁱ	3.4274 (6)	Si1—O4	1.6184 (15)
Y2—O5	2.0561 (15)	Si1—O2	1.6343 (17)

O5—Y1—O1ⁱ	100.43 (6)	O3^vi—Y2—Y2^v	113.71 (4)
O5—Y1—O3ⁱⁱ	76.88 (6)	O2—Y2—Y2^v	85.70 (5)
O1ⁱ—Y1—O3ⁱⁱ	146.27 (6)	O4^vii—Y2—Y2^v	109.24 (4)
O5—Y1—O2ⁱⁱⁱ	145.64 (6)	O4^viii—Y2—Y2^v	144.42 (4)
O1ⁱ—Y1—O2ⁱⁱⁱ	108.94 (7)	O5^v—Y2—Y2^v	37.04 (4)
O3ⁱⁱ—Y1—O2ⁱⁱⁱ	87.77 (6)	Si1^vii—Y2—Y2^v	100.045 (11)
O5—Y1—O1^iv	86.41 (6)	Y1^v—Y2—Y2^v	72.819 (10)
O1ⁱ—Y1—O1^iv	69.95 (7)	O5—Y2—Si1^viii	86.62 (4)
O3ⁱⁱ—Y1—O1^iv	76.33 (6)	O3^vi—Y2—Si1^viii	116.77 (4)
O2ⁱⁱⁱ—Y1—O1^iv	119.88 (6)	O2—Y2—Si1^viii	67.20 (5)
O5—Y1—O5ⁱⁱⁱ	75.56 (6)	O4^vii—Y2—Si1^viii	90.10 (4)
O1ⁱ—Y1—O5ⁱⁱⁱ	125.83 (6)	O4^viii—Y2—Si1^viii	23.26 (4)
O3ⁱⁱ—Y1—O5ⁱⁱⁱ	86.58 (5)	O5^v—Y2—Si1^viii	148.18 (4)
O2ⁱⁱⁱ—Y1—O5ⁱⁱⁱ	72.97 (6)	Si1^vii—Y2—Si1^viii	115.724 (13)
O1^iv—Y1—O5ⁱⁱⁱ	157.61 (6)	Y1^v—Y2—Si1^viii	157.784 (14)
O5—Y1—O2ⁱ	107.65 (6)	Y2^v—Y2—Si1^viii	124.750 (15)
O1ⁱ—Y1—O2ⁱ	61.04 (6)	O5—Y2—Y1ⁱⁱⁱ	42.78 (4)
O3ⁱⁱ—Y1—O2ⁱ	152.30 (5)	O3^vi—Y2—Y1ⁱⁱⁱ	138.22 (4)
O2ⁱⁱⁱ—Y1—O2ⁱ	73.25 (7)	O2—Y2—Y1ⁱⁱⁱ	41.25 (5)
O1^iv—Y1—O2ⁱ	130.56 (6)	O4^vii—Y2—Y1ⁱⁱⁱ	128.42 (4)
O5ⁱⁱⁱ—Y1—O2ⁱ	68.89 (5)	O4^viii—Y2—Y1ⁱⁱⁱ	84.31 (4)
O5—Y1—Si1ⁱ	101.83 (4)	O5^v—Y2—Y1ⁱⁱⁱ	88.99 (4)
O1ⁱ—Y1—Si1ⁱ	29.73 (4)	Si1^vii—Y2—Y1ⁱⁱⁱ	149.841 (14)
O3ⁱⁱ—Y1—Si1ⁱ	175.81 (4)	Y1^v—Y2—Y1ⁱⁱⁱ	126.661 (11)
O2ⁱⁱⁱ—Y1—Si1ⁱ	95.37 (5)	Y2^v—Y2—Y1ⁱⁱⁱ	66.734 (8)
O1^iv—Y1—Si1ⁱ	99.66 (5)	Si1^viii—Y2—Y1ⁱⁱⁱ	61.147 (11)
O5ⁱⁱⁱ—Y1—Si1ⁱ	96.99 (4)	O5—Y2—Y2^ix	104.20 (4)
O2ⁱ—Y1—Si1ⁱ	31.88 (4)	O3^vi—Y2—Y2^ix	98.49 (4)
O5—Y1—Y2^v	41.60 (4)	O2—Y2—Y2^ix	121.23 (5)
O1ⁱ—Y1—Y2^v	119.93 (5)	O4^vii—Y2—Y2^ix	36.49 (4)
O3ⁱⁱ—Y1—Y2^v	39.64 (4)	O4^viii—Y2—Y2^ix	35.87 (4)
O2ⁱⁱⁱ—Y1—Y2^v	126.94 (5)	O5^v—Y2—Y2^ix	155.46 (4)
O1^iv—Y1—Y2^v	64.72 (5)	Si1^vii—Y2—Y2^ix	60.627 (13)
O5ⁱⁱⁱ—Y1—Y2^v	92.89 (4)	Y1^v—Y2—Y2^ix	124.528 (14)
O2ⁱ—Y1—Y2^v	148.78 (4)	Y2^v—Y2—Y2^ix	135.245 (15)
Si1ⁱ—Y1—Y2^v	137.552 (13)	Si1^viii—Y2—Y2^ix	55.097 (12)
O5—Y1—Si1ⁱⁱⁱ	166.24 (4)	Y1ⁱⁱⁱ—Y2—Y2^ix	108.682 (13)
O1ⁱ—Y1—Si1ⁱⁱⁱ	93.15 (5)	O3—Si1—O1	111.91 (9)
O3ⁱⁱ—Y1—Si1ⁱⁱⁱ	90.63 (4)	O3—Si1—O4	111.74 (9)
O2ⁱⁱⁱ—Y1—Si1ⁱⁱⁱ	25.30 (4)	O1—Si1—O4	109.09 (9)
O1^iv—Y1—Si1ⁱⁱⁱ	96.33 (5)	O3—Si1—O2	112.47 (9)
O5ⁱⁱⁱ—Y1—Si1ⁱⁱⁱ	98.24 (4)	O1—Si1—O2	103.39 (10)
O2ⁱ—Y1—Si1ⁱⁱⁱ	80.78 (4)	O4—Si1—O2	107.83 (9)
Si1ⁱ—Y1—Si1ⁱⁱⁱ	91.025 (16)	O3—Si1—Y1^x	117.82 (6)
Y2^v—Y1—Si1ⁱⁱⁱ	128.233 (13)	O1—Si1—Y1^x	41.69 (7)
O5—Y1—Y2ⁱⁱⁱ	107.28 (4)	O4—Si1—Y1^x	129.19 (6)
O1ⁱ—Y1—Y2ⁱⁱⁱ	134.64 (5)	O2—Si1—Y1^x	62.86 (7)
O3ⁱⁱ—Y1—Y2ⁱⁱⁱ	76.13 (4)	O3—Si1—Y2^xi	116.29 (6)
O2ⁱⁱⁱ—Y1—Y2ⁱⁱⁱ	38.56 (4)	O1—Si1—Y2^xi	72.98 (7)
O1^iv—Y1—Y2ⁱⁱⁱ	145.32 (5)	O4—Si1—Y2^xi	38.01 (6)
O5ⁱⁱⁱ—Y1—Y2ⁱⁱⁱ	36.89 (4)	O2—Si1—Y2^xi	128.51 (7)
O2ⁱ—Y1—Y2ⁱⁱⁱ	76.49 (3)	Y1^x—Si1—Y2^xi	105.651 (17)
Si1ⁱ—Y1—Y2ⁱⁱⁱ	108.053 (13)	O3—Si1—Y1ⁱⁱⁱ	138.64 (6)
Y2^v—Y1—Y2ⁱⁱⁱ	104.472 (9)	O1—Si1—Y1ⁱⁱⁱ	103.68 (7)
Si1ⁱⁱⁱ—Y1—Y2ⁱⁱⁱ	63.400 (11)	O4—Si1—Y1ⁱⁱⁱ	73.78 (6)
O5—Y1—Si1ⁱⁱ	96.94 (4)	O2—Si1—Y1ⁱⁱⁱ	36.18 (7)
O1ⁱ—Y1—Si1ⁱⁱ	150.67 (5)	Y1^x—Si1—Y1ⁱⁱⁱ	76.588 (14)
O3ⁱⁱ—Y1—Si1ⁱⁱ	22.67 (4)	Y2^xi—Si1—Y1ⁱⁱⁱ	93.387 (15)
O2ⁱⁱⁱ—Y1—Si1ⁱⁱ	65.12 (5)	O3—Si1—Y2^viii	83.66 (6)
O1^iv—Y1—Si1ⁱⁱ	87.88 (5)	O1—Si1—Y2^viii	136.92 (8)
O5ⁱⁱⁱ—Y1—Si1ⁱⁱ	81.35 (4)	O4—Si1—Y2^viii	32.02 (6)
O2ⁱ—Y1—Si1ⁱⁱ	134.30 (4)	O2—Si1—Y2^viii	106.95 (7)
Si1ⁱ—Y1—Si1ⁱⁱ	160.129 (19)	Y1^x—Si1—Y2^viii	158.163 (19)
Y2^v—Y1—Si1ⁱⁱ	62.239 (11)	Y2^xi—Si1—Y2^viii	64.276 (13)
Si1ⁱⁱⁱ—Y1—Si1ⁱⁱ	69.770 (15)	Y1ⁱⁱⁱ—Si1—Y2^viii	84.489 (13)
Y2ⁱⁱⁱ—Y1—Si1ⁱⁱ	59.418 (11)	O3—Si1—Y1^xii	32.38 (6)
O5—Y2—O3^vi	154.24 (6)	O1—Si1—Y1^xii	144.23 (7)
O5—Y2—O2	81.14 (6)	O4—Si1—Y1^xii	91.34 (6)
O3^vi—Y2—O2	97.47 (6)	O2—Si1—Y1^xii	97.46 (7)
O5—Y2—O4^vii	98.91 (6)	Y1^x—Si1—Y1^xii	137.855 (18)
O3^vi—Y2—O4^vii	92.07 (6)	Y2^xi—Si1—Y1^xii	115.049 (17)
O2—Y2—O4^vii	157.29 (7)	Y1ⁱⁱⁱ—Si1—Y1^xii	110.232 (15)
O5—Y2—O4^viii	103.92 (6)	Y2^viii—Si1—Y1^xii	59.436 (11)
O3^vi—Y2—O4^viii	101.60 (6)	Si1—O1—Y1^x	108.57 (10)
O2—Y2—O4^viii	85.52 (7)	Si1—O1—Y1^xiii	141.32 (11)
O4^vii—Y2—O4^viii	72.36 (7)	Y1^x—O1—Y1^xiii	110.05 (7)
O5—Y2—O5^v	76.95 (6)	Si1—O2—Y2	139.18 (11)
O3^vi—Y2—O5^v	77.34 (6)	Si1—O2—Y1ⁱⁱⁱ	118.51 (10)
O2—Y2—O5^v	83.30 (7)	Y2—O2—Y1ⁱⁱⁱ	100.19 (7)
O4^vii—Y2—O5^v	119.01 (6)	Si1—O2—Y1^x	85.26 (8)
O4^viii—Y2—O5^v	168.51 (6)	Y2—O2—Y1^x	97.12 (7)
O5—Y2—Si1^vii	109.40 (4)	Y1ⁱⁱⁱ—O2—Y1^x	105.46 (7)
O3^vi—Y2—Si1^vii	71.56 (4)	Si1—O3—Y2^xiv	136.44 (9)
O2—Y2—Si1^vii	168.91 (5)	Si1—O3—Y1^xii	124.95 (9)
O4^vii—Y2—Si1^vii	27.74 (4)	Y2^xiv—O3—Y1^xii	98.28 (6)
O4^viii—Y2—Si1^vii	94.94 (4)	Si1—O4—Y2^xi	114.25 (9)
O5^v—Y2—Si1^vii	95.53 (4)	Si1—O4—Y2^viii	124.73 (9)
O5—Y2—Y1^v	113.05 (4)	Y2^xi—O4—Y2^viii	107.64 (7)
O3^vi—Y2—Y1^v	42.08 (4)	Y2—O5—Y1	140.24 (8)
O2—Y2—Y1^v	104.33 (5)	Y2—O5—Y2^v	102.36 (6)
O4^vii—Y2—Y1^v	96.57 (4)	Y1—O5—Y2^v	98.75 (6)
O4^viii—Y2—Y1^v	142.71 (4)	Y2—O5—Y1ⁱⁱⁱ	100.33 (6)
O5^v—Y2—Y1^v	39.66 (4)	Y1—O5—Y1ⁱⁱⁱ	104.44 (6)
Si1^vii—Y2—Y1^v	68.834 (12)	Y2^v—O5—Y1ⁱⁱⁱ	108.34 (6)
O5—Y2—Y2^v	40.59 (4)

Symmetry codes: (i) x, −y+1, z−1/2; (ii) x+1/2, y+1/2, z; (iii) −x+1, −y+1, −z+1; (iv) −x+1, y+1, −z+3/2; (v) −x+1, y, −z+3/2; (vi) −x+1/2, y+1/2, −z+3/2; (vii) x, y+1, z; (viii) −x+1/2, −y+1/2, −z+1; (ix) −x+1/2, −y+3/2, −z+1; (x) x, −y+1, z+1/2; (xi) x, y−1, z; (xii) x−1/2, y−1/2, z; (xiii) −x+1, y−1, −z+3/2; (xiv) −x+1/2, y−1/2, −z+3/2.

Atom positions, occupancy parameters and isotropic displacement parameters (Å^-3) top

Atom	Occupancy parameter (µ)	x	y	z	U_iso/U_eq
Sc1/Y1	0.473 (6)/0.527 (6)	0.54003 (2)	0.74582 (3)	0.47192 (3)	0.00629 (10)
Sc2/Y2	0.895 (4)/0.105 (4)	0.35953 (3)	0.62123 (5)	0.65961 (3)	0.00489 (11)
Si	1	0.31652 (4)	0.09224 (8)	0.69201 (6)	0.00455 (14)
O1	1	0.41423 (14)	0.0143 (3)	0.86269 (19)	0.0156 (3)
O2	1	0.37268 (15)	0.2941 (3)	0.6622 (2)	0.0141 (3)
O3	1	0.20114 (13)	0.1458 (2)	0.68586 (18)	0.0088 (3)
O4	1	0.29676 (14)	-0.0798 (2)	0.56393 (18)	0.0102 (3)
O5	1	0.48321 (12)	0.5961 (2)	0.60705 (17)	0.0070 (2)

Bond lengths (Å) and angles (°) in Sc_1.368Y_0.632SiO₅ RE1 is Sc1/Y1 and RE2 is Sc2/Y1. top

Sc/Y polyhedron		SiO₄ tetrahedra
Sc1/Y1—O5	2.1349 (14)	Si1—O3	1.6120 (16)
Sc1/Y1—O1	2.1641 (19)	Si1—O1	1.6136 (16)
Sc1/Y1—O3	2.2391 (15)	Si1—O4	1.6184 (15)
Sc1/Y1—O2	2.2571 (18)	Si1—O2	1.6343 (17)
Sc1/Y1—O1	2.2614 (18)	Average	1.620 (2)
Sc1/Y1—O5	2.3262 (15)
Sc1/Y1—O2	2.754 (2)	O1—Si1—O3	111.91 (9)
Average	2.305 (2)	O3—Si1—O4	111.74 (9)
		O1—Si1—O4	109.09 (9)
Sc2/Y1—O5	2.0561 (15)	O2—Si1—O3	112.47 (9)
Sc2/Y1—O3	2.1316 (15)	O1—Si1—O2	103.39 (10)
Sc2/Y1—O2	2.1341 (18)	O2—Si1—O4	107.83 (9)
Sc2/Y1—O4	2.1415 (17)	Average	109.4 (1)
Sc2/Y1—O4	2.1733 (16)
Sc2/Y1—O5	2.2208 (15)
Average	2.143 (2)

Occupancy site in RE1_2-_xRE2_xSiO₅ structures and polyhedra distortion data top

Composition	Δr	µ (CN7)	µ (CN6)	R_av(CN7)	Δr(CN7)	D(CN7)	R_av(CN6)	Δr(CN6)	D(CN6)	Reference
Sc₂SiO₅	–	1	1	2.276	0.992	1.8× 10^-2	2.132	0.175	8× 10^-4	Alba et al. (2009)
Er₂SiO₅	-	1	1	2.347	0.417	2.6× 10^-3	2.258	0.082	1.3× 10^-4	Phanon et al. (2008)
Lu₂SiO₅	-	1	1	2.324	0.454	3.16× 10^-3	2.228	0.096	1.75× 10^-4	Gustafsson et al. (2001)
Y₂SiO₅	-	1	1	2.360	0.406	2.38× 10^-3	2.272	0.076	1.2× 10^-4	Li (1999)
Lu_1.82Y_0.18SiO₅	0.039	0.116Y/0.884Lu	0.072Y/0.938Lu	2.322	0.452	3.2× 10^-3	2.232	0.115	2.5× 10^-4	Ding et al. (2014)
Lu_1.404Y_0.596SiO₅	0.039	0.361Y/0.639Lu	0.223Y/0.777Lu	2.333	0.456	3.2× 10^-3	2.236	0.104	2.2× 10^-4	Ding et al. (2014)
Lu₀₉₆Y_1.04SiO₅	0.039	0.613Y/0.387Lu	0.423Y/0.577Lu	2.341	0.439	2.8× 10^-3	2.246	0.103	2.1× 10^-4	Ding et al. (2014)
Lu_0.61Y_1.39SiO₅	0.039	0.775Y/0.225Lu	0.619Y/0.381Lu	2.349	0.426	2.7× 10^-3	2.252	0.100	2.2× 10^-4	Ding et al. (2014)
Lu_0.194Y_1.806SiO₅	0.039	0.93Y/0.07Lu	0.875/0.125	2.354	0.409	2.4× 10^-3	2.260	0.077	1.4× 10^-4	Ding et al. (2014)
Lu_1.50Sc_0.50SiO₅	0.116	0.93Lu/0.07Sc	0.57Lu//0.43Sc	2.309	0.469	3.7× 10^-3	2.183	0.105	2.4× 10^-4	Ben Yahia et al. (2011)
Lu_1.23Sc_0.77SiO₅	0.116	0.82Lu/0.18Sc	0.41Lu//0.59Sc	2.309	0.499	4.3× 10^-3	2.170	0.136	7.9× 10^-4	Ben Yahia et al. (2011)
Lu_1.12Sc_0.88SiO₅	0.116	0.773Lu/0.227Sc	0.346Lu//0.654Sc	2.303	0.526	4.8× 10^-3	2.166	0.141	3.9× 10^-4	Ben Yahia et al. (2011)
Sc_1.368Y_0.632SiO₅	0.155	0.527Y/0.473Sc	0.105Y/0.895Sc	2.305	0.619	6.97× 10^-3	2.143	0.165	5.34× 10^-4	*
Sc₁.₉₃₁Tm₀.₀₆₉SiO₅	0.135	0.069Tm/0.931Sc	0Tm/100Sc	2.276	0.878	1.46× 10^-2	2.121	0.179	6.8× 10^-4	Rodewald et al. (2012)
Sc₁.₉₅₅Yb₀.₀₄₅SiO₅	0.123	0.045Yb/0.955Sc	0Yb/100Sc	2.282	0.901	1.52× 10^-2	2.128	0.175	6.6× 10^-4	Rodewald et al. (2012)
Lu_1.923Ce_0.077SiO₅	0.149	0.069Ce/0.931Lu	0.003Ce/0.997Lu	**	**	**	**	**	**	Buryi et al. (2016)

Notes: (*) this work; (**) data in Buryi et al. (2016) are absent.

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