Three different Ge environments in a new Sr₅CuGe₉O₂₄ phase synthesized at high pressure and high tem­per­ature

In the framework of expanding the range of copper-based compounds in the pyroxene family, we have synthesized at high pressure and high tem­per­ature a powder containing a mixture of a new phase with stoichiometry Sr₅CuGe₉O₂₄ having two identified impurity phases. Electron crystallography showed that the new phase crystallizes in the monoclinic space group P2/c, with unit-cell parameters a = 11.8 Å, b = 8.1 Å, c = 10.3 Å and β = 101.3°. We applied the recently developed low-dose electron diffraction tomography method to solve the structure by direct methods. The obtained structure model contains all 9 independent cation positions and all 13 oxygen positions. A subsequent refinement against powder X-ray diffraction data ascertained the high quality of the structure solution, in particular, the unusual structural arrangement that there are three different environments for Ge in this phase.

Computing details

(I)

Crystal data

CuGe9O24·5(Sr)	β = 101.5972 (13)°
Mr = 1538.9	V = 984.44 (4) Å^3
Monoclinic, P2/c	Z = 2
Hall symbol: -P 2yc	F(000) = 488
a = 11.8817 (3) Å	Dx = 5.192 Mg m^−3
b = 8.19277 (17) Å	Cu Kα1 radiation
c = 10.3237 (2) Å	T = 293 K

Data collection

Bruker D5000 diffractometer	Ge 111 monochromator
Radiation source: sealed X-ray tube	2θmin = 10°, 2θmax = 90.317°, 2θstep = 0.032°

Refinement

Rp = 0.028	0 restraints
Rwp = 0.038	14 constraints
Rexp = 0.024	Weighting scheme based on measured s.u.'s
R(F) = 0.028	(Δ/σ)max = 0.024
2515 data points	Background function: 19 Legendre polynoms
Profile function: Pseudo-Voigt	Preferred orientation correction: none
110 parameters

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

	x	y	z	Uiso*/Ueq
Sr1	1	−0.6469 (8)	0.75	0.007 (2)*
Sr2	0.7559 (4)	0.0316 (5)	0.6837 (4)	0.0047 (16)*
Sr3	0.6505 (4)	−0.5151 (5)	0.6817 (5)	0.0080 (15)*
Ge1	0.8529 (5)	−0.2890 (6)	0.9356 (5)	0.0054 (17)*
Ge2	0.5889 (4)	0.1750 (7)	0.3708 (6)	0.0119 (19)*
Ge3	0.7896 (5)	−0.3288 (7)	0.4766 (5)	0.0072 (16)*
Ge4	0.5412 (4)	−0.1599 (7)	0.4122 (6)	0.0095 (18)*
Ge5	1	−0.2199 (9)	0.75	0.008 (2)*
Cu1	1	0	1	0.006 (3)*
O1	0.797 (2)	−0.305 (3)	0.315 (3)	0.011 (2)*
O2	0.544 (2)	−0.036 (3)	0.630 (3)	0.011 (2)*
O3	0.944 (2)	−0.407 (3)	0.827 (3)	0.011 (2)*
O4	0.647 (2)	−0.325 (3)	0.489 (3)	0.011 (2)*
O5	0.415 (2)	−0.264 (3)	0.469 (3)	0.011 (2)*
O6	0.671 (2)	−0.023 (3)	0.421 (3)	0.011 (2)*
O7	0.5	0.344 (5)	0.25	0.011 (2)*
O8	0.909 (2)	−0.182 (3)	1.065 (3)	0.011 (2)*
O9	0.869 (2)	−0.216 (3)	0.595 (3)	0.011 (2)*
O10	0.716 (2)	−0.276 (3)	0.836 (3)	0.011 (2)*
O11	0.817 (2)	−0.473 (3)	1.026 (2)	0.011 (2)*
O12	0.5	−0.260 (4)	0.25	0.011 (2)*
O13	0.909 (2)	−0.079 (3)	0.820 (3)	0.011 (2)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
?	?	?	?	?	?	?

Geometric parameters (Å, º)

Sr1—O1^i	2.66 (3)	Ge2—O2^vii	1.95 (3)
Sr1—O1^ii	2.66 (3)	Ge2—O2^viii	2.69 (3)
Sr1—O3	2.28 (2)	Ge2—O5^vii	1.82 (3)
Sr1—O3^iii	2.28 (2)	Ge2—O6	1.91 (3)
Sr1—O8^iv	2.44 (3)	Ge2—O7	2.02 (3)
Sr1—O8^v	2.44 (3)	Ge2—O10^viii	1.83 (3)
Sr1—O11^iv	3.01 (2)	Ge3—O1	1.70 (3)
Sr1—O11^v	3.01 (2)	Ge3—O4	1.73 (3)
Sr2—O1^vi	2.61 (3)	Ge3—O6	2.87 (3)
Sr2—O2	2.52 (3)	Ge3—O9	1.67 (3)
Sr2—O5^vii	2.99 (2)	Ge3—O11^v	1.71 (3)
Sr2—O6	2.74 (3)	Ge4—O2	2.46 (3)
Sr2—O6^vi	2.83 (3)	Ge4—O2^vii	1.90 (3)
Sr2—O8^viii	2.69 (3)	Ge4—O4	1.90 (3)
Sr2—O9	2.69 (3)	Ge4—O5	1.92 (3)
Sr2—O10	3.06 (3)	Ge4—O6	1.89 (3)
Sr2—O13	2.25 (2)	Ge4—O12	1.841 (17)
Sr3—O1^ii	2.47 (2)	Ge5—O3	1.91 (3)
Sr3—O4	2.52 (3)	Ge5—O3^iii	1.91 (3)
Sr3—O5^ix	2.41 (3)	Ge5—O9	1.99 (2)
Sr3—O7^vii	2.48 (2)	Ge5—O9^iii	1.99 (2)
Sr3—O10	2.54 (3)	Ge5—O13	1.83 (3)
Sr3—O11^v	2.79 (3)	Ge5—O13^iii	1.83 (3)
Sr3—O12^ix	2.76 (2)	Cu1—O8	2.03 (3)
Ge1—O3	1.96 (3)	Cu1—O8^x	2.03 (3)
Ge1—O8	1.62 (3)	Cu1—O9^iii	2.67 (3)
Ge1—O10	1.74 (3)	Cu1—O9^vi	2.67 (3)
Ge1—O11	1.87 (3)	Cu1—O13	2.05 (2)
Ge1—O13	2.27 (3)	Cu1—O13^x	2.05 (2)
O1^i—Sr1—O1^ii	163.0 (8)	O10—Sr3—O12^ix	119.2 (8)
O1^i—Sr1—O3	124.2 (9)	O11^v—Sr3—O12^ix	134.2 (8)
O1^i—Sr1—O3^iii	72.2 (9)	O3—Ge1—O8	123.4 (12)
O1^i—Sr1—O8^iv	80.3 (9)	O3—Ge1—O10	104.2 (13)
O1^i—Sr1—O8^v	89.9 (9)	O3—Ge1—O11	95.5 (11)
O1^i—Sr1—O11^iv	71.8 (8)	O3—Ge1—O13	79.7 (10)
O1^i—Sr1—O11^v	114.2 (8)	O8—Ge1—O10	129.6 (13)
O1^ii—Sr1—O3	72.2 (9)	O8—Ge1—O11	97.1 (13)
O1^ii—Sr1—O3^iii	124.2 (9)	O8—Ge1—O13	84.6 (12)
O1^ii—Sr1—O8^iv	89.9 (9)	O10—Ge1—O11	93.6 (11)
O1^ii—Sr1—O8^v	80.3 (9)	O10—Ge1—O13	88.9 (11)
O1^ii—Sr1—O11^iv	114.2 (8)	O11—Ge1—O13	175.0 (11)
O1^ii—Sr1—O11^v	71.8 (8)	O2^vii—Ge2—O2^viii	75.0 (10)
O3—Sr1—O3^iii	60.2 (10)	O2^vii—Ge2—O5^vii	93.9 (12)
O3—Sr1—O8^iv	109.7 (9)	O2^vii—Ge2—O6	82.7 (11)
O3—Sr1—O8^v	131.1 (9)	O2^vii—Ge2—O7	94.3 (9)
O3—Sr1—O11^iv	70.4 (8)	O2^vii—Ge2—O10^viii	166.0 (12)
O3—Sr1—O11^v	76.6 (8)	O2^viii—Ge2—O5^vii	167.4 (10)
O3^iii—Sr1—O8^iv	131.1 (9)	O2^viii—Ge2—O6	83.4 (10)
O3^iii—Sr1—O8^v	109.7 (9)	O2^viii—Ge2—O7	74.8 (9)
O3^iii—Sr1—O11^iv	76.6 (8)	O2^viii—Ge2—O10^viii	91.4 (11)
O3^iii—Sr1—O11^v	70.4 (8)	O5^vii—Ge2—O6	101.6 (12)
O8^iv—Sr1—O8^v	109.9 (9)	O5^vii—Ge2—O7	100.4 (10)
O8^iv—Sr1—O11^iv	56.5 (8)	O5^vii—Ge2—O10^viii	99.9 (12)
O8^iv—Sr1—O11^v	158.2 (8)	O6—Ge2—O7	157.9 (11)
O8^v—Sr1—O11^iv	158.2 (8)	O6—Ge2—O10^viii	92.4 (11)
O8^v—Sr1—O11^v	56.5 (8)	O7—Ge2—O10^viii	85.2 (9)
O11^iv—Sr1—O11^v	141.7 (8)	O1—Ge3—O4	108.1 (13)
O1^vi—Sr2—O2	112.0 (8)	O1—Ge3—O6	79.8 (10)
O1^vi—Sr2—O5^vii	76.2 (7)	O1—Ge3—O9	121.9 (13)
O1^vi—Sr2—O6	130.4 (8)	O1—Ge3—O11^v	111.0 (12)
O1^vi—Sr2—O6^vi	68.5 (8)	O4—Ge3—O6	63.2 (11)
O1^vi—Sr2—O8^viii	76.7 (9)	O4—Ge3—O9	110.9 (14)
O1^vi—Sr2—O9	140.2 (8)	O4—Ge3—O11^v	97.1 (12)
O1^vi—Sr2—O10	118.3 (8)	O6—Ge3—O9	81.4 (10)
O1^vi—Sr2—O13	88.7 (8)	O6—Ge3—O11^v	160.0 (10)
O2—Sr2—O5^vii	59.0 (8)	O9—Ge3—O11^v	105.0 (12)
O2—Sr2—O6	65.9 (8)	O2—Ge4—O2^vii	76.7 (10)
O2—Sr2—O6^vi	70.8 (8)	O2—Ge4—O4	91.5 (10)
O2—Sr2—O8^viii	137.4 (8)	O2—Ge4—O5	77.0 (10)
O2—Sr2—O9	107.6 (8)	O2—Ge4—O6	81.5 (11)
O2—Sr2—O10	71.5 (7)	O2—Ge4—O12	165.4 (7)
O2—Sr2—O13	133.8 (9)	O2^vii—Ge4—O4	166.1 (11)
O5^vii—Sr2—O6	60.4 (8)	O2^vii—Ge4—O5	91.8 (11)
O5^vii—Sr2—O6^vi	98.4 (8)	O2^vii—Ge4—O6	84.4 (11)
O5^vii—Sr2—O8^viii	85.3 (8)	O2^vii—Ge4—O12	97.9 (12)
O5^vii—Sr2—O9	129.4 (8)	O4—Ge4—O5	92.7 (11)
O5^vii—Sr2—O10	129.7 (7)	O4—Ge4—O6	86.6 (11)
O5^vii—Sr2—O13	164.0 (8)	O4—Ge4—O12	95.3 (12)
O6—Sr2—O6^vi	136.7 (7)	O5—Ge4—O6	158.4 (12)
O6—Sr2—O8^viii	76.9 (8)	O5—Ge4—O12	89.8 (10)
O6—Sr2—O9	69.6 (8)	O6—Ge4—O12	111.8 (10)
O6—Sr2—O10	108.0 (8)	O3—Ge5—O3^iii	73.4 (12)
O6—Sr2—O13	130.2 (9)	O3—Ge5—O9	93.7 (11)
O6^vi—Sr2—O8^viii	142.8 (8)	O3—Ge5—O9^iii	87.7 (11)
O6^vi—Sr2—O9	124.3 (8)	O3—Ge5—O13	93.2 (12)
O6^vi—Sr2—O10	54.4 (8)	O3—Ge5—O13^iii	163.3 (11)
O6^vi—Sr2—O13	80.4 (9)	O3^iii—Ge5—O9	87.7 (11)
O8^viii—Sr2—O9	76.2 (8)	O3^iii—Ge5—O9^iii	93.7 (11)
O8^viii—Sr2—O10	143.1 (8)	O3^iii—Ge5—O13	163.3 (11)
O8^viii—Sr2—O13	86.1 (9)	O3^iii—Ge5—O13^iii	93.2 (12)
O9—Sr2—O10	71.9 (8)	O9—Ge5—O9^iii	178.3 (11)
O9—Sr2—O13	61.0 (9)	O9—Ge5—O13	83.1 (11)
O10—Sr2—O13	62.4 (8)	O9—Ge5—O13^iii	95.8 (11)
O1^ii—Sr3—O4	135.0 (9)	O9^iii—Ge5—O13	95.8 (11)
O1^ii—Sr3—O5^ix	90.6 (8)	O9^iii—Ge5—O13^iii	83.1 (11)
O1^ii—Sr3—O7^vii	130.0 (8)	O13—Ge5—O13^iii	101.5 (12)
O1^ii—Sr3—O10	91.0 (8)	O8—Cu1—O8^x	180
O1^ii—Sr3—O11^v	78.5 (9)	O8—Cu1—O9^iii	91.1 (10)
O1^ii—Sr3—O12^ix	83.0 (7)	O8—Cu1—O9^vi	88.9 (10)
O4—Sr3—O5^ix	90.1 (9)	O8—Cu1—O13	81.4 (10)
O4—Sr3—O7^vii	88.7 (8)	O8—Cu1—O13^x	98.6 (10)
O4—Sr3—O10	88.5 (9)	O8^x—Cu1—O9^iii	88.9 (10)
O4—Sr3—O11^v	57.9 (8)	O8^x—Cu1—O9^vi	91.1 (10)
O4—Sr3—O12^ix	134.8 (6)	O8^x—Cu1—O13	98.6 (10)
O5^ix—Sr3—O7^vii	116.7 (8)	O8^x—Cu1—O13^x	81.4 (10)
O5^ix—Sr3—O10	178.4 (9)	O9^iii—Cu1—O9^vi	180
O5^ix—Sr3—O11^v	77.1 (9)	O9^iii—Cu1—O13	72.5 (9)
O5^ix—Sr3—O12^ix	61.4 (8)	O9^iii—Cu1—O13^x	107.5 (9)
O7^vii—Sr3—O10	62.5 (8)	O9^vi—Cu1—O13	107.5 (9)
O7^vii—Sr3—O11^v	144.8 (9)	O9^vi—Cu1—O13^x	72.5 (9)
O7^vii—Sr3—O12^ix	76.2 (9)	O13—Cu1—O13^x	180
O10—Sr3—O11^v	102.8 (9)

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