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The binary phase diagram of Cu–Si is unexpectedly complex in the vicinity of Cu3+xSi. The low-temperature region contains three closely related incommensurately modulated phases denoted, in order of increasing temperature of stability, η′′′, η′′ and η′. The structure analysis of η′ has been reported previously [Palatinus et al. (2011). Inorg. Chem. 50, 3743]. Here the structure model for the phases η′′ and η′′′ is reported. The structures could be solved in superspace, but no superspace structure model could be constructed due to the complexity of the modulation functions. Therefore, the structures were described in a supercell approximation, which involved a 4 × 4 × 3 supercell for the η′′ phase and a 14 × 14 × 3 supercell for the η′′′ phase. Both structures are very similar and differ only by a subtle symmetry lowering from η′′ to η′′′. A comparison of the structure models of η′′ and η′′′ with the reported structure of η′ suggests that the reported structure model of η′ contains an incorrect assignment of atomic types.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S2052520617006163/bp5097sup1.cif
Contains datablocks global, eta1, eta2

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S2052520617006163/bp5097eta1sup2.hkl
Contains datablock eta1

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S2052520617006163/bp5097eta2sup3.hkl
Contains datablock eta2

CCDC references: 1545784; 1545785

Computing details top

For both structures, data collection: Bruker SAINT, v. 8.34A; cell refinement: Bruker SAINT, v. 8.34A; data reduction: Bruker SAINT, v. 8.34A, SADABS (Sheldrick 1996); program(s) used to solve structure: Supeflip (Palatinus and Chapuis, 2007); program(s) used to refine structure: Jana2006 (Petricek et al., 2014).

(eta1) top
Crystal data top
Cu3.313SiDx = 7.563 Mg m3
Mr = 238.6Mo Kα radiation, λ = 0.71073 Å
Trigonal, P31cCell parameters from 1361 reflections
Hall symbol: -P 3;-2cθ = 5.6–28.9°
a = 16.2448 (4) ŵ = 33.35 mm1
c = 44.017 (8) ÅT = 743 K
V = 10060 (2) Å3Irregular, metallic gray
Z = 1920.16 × 0.13 × 0.09 mm
F(000) = 21132
Data collection top
KappaCCD (Bruker-Nonius)
diffractometer
624 reflections with I > 3σ(I)
Graphite monochromatorRint = 0.240
phi–scanθmax = 30.4°, θmin = 2.7°
Absorption correction: multi-scan
SADABS (J.Appl.Cryst.48 (2015). )
h = 2322
Tmin = 0.420, Tmax = 0.746k = 2323
25292 measured reflectionsl = 6261
4996 independent reflections
Refinement top
Refinement on F0 restraints
R[F2 > 2σ(F2)] = 0.150282 constraints
wR(F2) = 0.159Weighting scheme based on measured s.u.'s w = 1/(σ2(F) + 0.0001F2)
S = 2.35(Δ/σ)max = 0.003
4996 reflectionsΔρmax = 13.76 e Å3
6 parametersΔρmin = 14.71 e Å3
Special details top

Refinement. In reality incommensurately modulated structure. Model obtained by solution of a large supercell. Coordinates fixed to values from solution, isotropic displacement parameters refined, but fixed to be constant in each crystallographicaly independent layer. Reflections limited only to main reflections and satellites of the incommensurate structure.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/UeqOcc. (<1)
Cu020010.3304880.4205530.0216410.0264 (4)*
Cu020020.3501990.1473120.0247880.0264 (4)*
Cu020030.6707820.0903320.0233230.0264 (4)*
Cu020040.8296690.9166230.0249260.0264 (4)*
Cu020050.5528510.1529520.026120.0264 (4)*
Cu020060.3333330.6666670.0241150.0264 (4)*
Cu020070.1484190.3555040.0273230.0264 (4)*
Cu020080.3767040.0040080.0279710.0264 (4)*
Cu020090.150830.5514750.0299660.0264 (4)*
Cu020100.9080290.0815610.031210.0264 (4)*
Cu020110.6666670.3333330.0304430.0264 (4)*
Cu03001000.0535690.0190 (3)*
Cu030020.2527090.2598150.0549540.0190 (3)*
Cu030030.5038120.2587870.0554810.0190 (3)*
Cu030040.2666950.5108910.0549930.0190 (3)*
Cu030050.5108990.0020510.0559460.0190 (3)*
Cu030060.2425291.0001120.0564450.0190 (3)*
Cu040010.0853960.4192950.07940.0184 (4)*
Cu040020.3299060.165640.0820230.0184 (4)*
Cu040030.3328620.4181980.0832940.0184 (4)*
Cu040040.0869410.1690490.0854570.0184 (4)*
Cu040050.5802910.1657540.0849930.0184 (4)*
Cu040060.3333330.6666670.0878670.0184 (4)*
Cu05001000.1102090.0190 (3)*
Cu050020.2423120.4874960.1103660.0190 (3)*
Cu050030.7537740.2433120.1106870.0190 (3)*
Cu050040.7414110.0031010.1113050.0190 (3)*
Cu050050.4923420.4995520.1115250.0190 (3)*
Cu050060.260311.0005110.1121330.0190 (3)*
Cu060010.4314540.0886620.1354670.0264 (4)*
Cu060020.2159520.6093820.137460.0264 (4)*
Cu060030.1550290.3127040.1391010.0264 (4)*
Cu060040.6104460.2175920.1403020.0264 (4)*
Cu060050.0890340.428840.1411280.0264 (4)*
Cu060060.3192420.1568510.1426990.0264 (4)*
Cu060070.6635120.0893420.1426780.0264 (4)*
Cu060080.3358950.4280340.1445270.0264 (4)*
Cu080010.6666670.3333330.1896420.0264 (4)*
Cu080020.1806210.0859330.1897410.0264 (4)*
Cu080030.3333330.6666670.1909370.0264 (4)*
Cu080040.4101020.5617120.1892820.0264 (4)*
Cu080050.0821270.1721190.1904330.0264 (4)*
Cu080060.4147490.0871430.1925050.0264 (4)*
Cu080070.2096130.3570230.193020.0264 (4)*
Cu080080.5965190.1503570.1934810.0264 (4)*
Cu080090.6198490.9964590.1943640.0264 (4)*
Cu080100.7912240.1457810.1966530.0264 (4)*
Cu080110.0913530.41310.19860.0264 (4)*
Cu090010.2520890.0052360.2209010.0190 (3)*
Cu09002000.2217250.0190 (3)*
Cu090030.5086360.2451790.2223730.0190 (3)*
Cu090040.2516880.5097330.2222950.0190 (3)*
Cu090050.4871960.0009960.2223680.0190 (3)*
Cu090060.7557640.0029120.2229330.0190 (3)*
Cu100010.1622380.0811190.250.0184 (4)*
Cu100020.1664640.5832320.250.0184 (4)*
Cu100030.6666670.3333330.250.0184 (4)*
Cu100040.1674640.3349280.250.0184 (4)*
Cu100050.4157340.0841710.2537360.0184 (4)*
Si010010.2474760.9999890.9991020.034 (9)*
Si010020.7417250.2506170.9990760.034 (9)*
Si010030.5000.034 (9)*
Si010040000.034 (9)*
Si040010.4178570.0814040.0786610.007 (3)*
Si040020.1625220.3312680.0814250.007 (3)*
Si040030.6702390.0832530.0840130.007 (3)*
Si040040.9183130.0816660.0846440.007 (3)*
Si040050.1673560.5844880.0855880.007 (3)*
Si040060.6666670.3333330.0898630.007 (3)*
Si070010.752411.0014340.1668930.007 (3)*
Si070020.4957080.001570.1654410.007 (3)*
Si070030.2536511.9928310.1677310.007 (3)*
Si070040.2472270.4997510.1671690.007 (3)*
Si070050.4942070.2436470.1656640.007 (3)*
Si07006000.1686190.007 (3)*
Si100010.5829140.1658280.250.034 (9)*
Si100020.082960.165920.250.034 (9)*
Si100030.3333330.6666670.250.034 (9)*
Si100040.3324320.1662160.250.034 (9)*
Si100050.0819150.4166040.2544740.034 (9)*
Cur1a0.0048250.1272750.1350.0264 (4)*0.1667
Cur1/1a0.1439120.0358540.1350.0264 (4)*0.1667
Cur1/2a0.0841170.1494340.1350.0264 (4)*0.1667
Cur1/3a0.0919250.0565010.1350.0264 (4)*0.1667
Cur1/4a0.140930.1145150.1350.0264 (4)*0.1667
Cur1b0.0048250.1272750.1350.0264 (4)*0.1667
Cur1/1b0.1439120.0358540.1350.0264 (4)*0.1667
Cur1/2b0.0841170.1494340.1350.0264 (4)*0.1667
Cur1/3b0.0919250.0565010.1350.0264 (4)*0.1667
Cur1/4b0.140930.1145150.1350.0264 (4)*0.1667
(eta2) top
Crystal data top
Cu3.311SiDx = 7.519 Mg m3
Mr = 238.5Mo Kα radiation, λ = 0.71073 Å
Trigonal, P3Cell parameters from 2251 reflections
Hall symbol: -P 3θ = 5.6–28.2°
a = 56.9800 (3) ŵ = 33.35 mm1
c = 44.055 (2) ÅT = 393 K
V = 123870 (6) Å3Irregular, metallic gray
Z = 23520.16 × 0.13 × 0.09 mm
F(000) = 258780
Data collection top
KappaCCD (Bruker-Nonius)
diffractometer
1471 reflections with I > 3σ(I)
Graphite monochromatorRint = 0.139
phi–scanθmax = 29.3°, θmin = 2.0°
Absorption correction: multi-scan
SADABS (J.Appl.Cryst.48 (2015). )
h = 7777
Tmin = 0.420, Tmax = 0.746k = 7777
25518 measured reflectionsl = 6059
4920 independent reflections
Refinement top
Refinement on F0 restraints
R[F2 > 2σ(F2)] = 0.1196777 constraints
wR(F2) = 0.137Weighting scheme based on measured s.u.'s w = 1/(σ2(F) + 0.0001F2)
S = 2.93(Δ/σ)max = 0.001
4920 reflectionsΔρmax = 12.91 e Å3
6 parametersΔρmin = 17.54 e Å3
Special details top

Refinement. In reality incommensurately modulated structure. Model obtained by solution of a large supercell. Coordinates fixed to values from solution, isotropic displacement parameters refined, but fixed to be constant in each crystallographicaly independent layer. Reflections limited only to main reflections and satellites of the incommensurate structure.

 

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