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The industrial importance of the U-Al-Si system stems from the fact that during processing the Al-based alloy (containing Si as impurity), used for the cladding of U (fuel in nuclear reactors), undergoes heat treatment which stimulates diffusion between the fuel and the cladding. One of the possible ways to represent the ternary U-Al-Si phase diagram is the construction of an UAl3-USi3 quasi-binary phase diagram. On the one hand, since the UAl3 and USi3 phases are isostructural, an isomorphous phase diagram is expected; on the other hand, some researchers observed a miscibility gap at lower temperatures. During our study of the UAl3-USi3 quasi-binary phase diagram, a new stable U(Alx,Si1 - x)3 phase was identified. The structure of this phase was determined, using a combination of electron crystallography and powder X-ray diffraction methods, as tetragonal [I4/mmm (No.139) space group], with lattice parameters a = b = 8.347 (1), c = 16.808 (96) Å. Its unit cell has 64 atoms and it can be described as an ordered variant of the U(Al,Si)3 solid solution. A Bärnighausen tree was constructed using the original U(Al,Si)3 structure as an aristotype.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S2052520614003801/hw5030sup1.cif
Contains datablock I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S2052520614003801/hw5030Isup2.hkl
Contains datablock I

CCDC reference: 987736

Computing details top

Program(s) used to refine structure: SHELXL97 (Sheldrick, 1997).

(I) top
Crystal data top
Al28Si20U16γ = 90°
Mr = 5125.72V = 1171.1 (5) Å3
a = 8.3471 (10) ÅZ = 4
b = 8.3471 (10) ÅF(000) = 2116
c = 16.809 (6) ÅDx = 7.268 Mg m3
α = 90°T = 293 K
β = 90°
Data collection top
Radiation source: fine-focus sealed tubeRint = 0.000
Graphite monochromatorθmax = 73.8°, θmin = 5.3°
400 measured reflectionsh = 010
400 independent reflectionsk = 07
400 reflections with I > 2σ(I)l = 020
Refinement top
Refinement on F20 restraints
Least-squares matrix: fullPrimary atom site location: structure-invariant direct methods
R[F2 > 2σ(F2)] = 0.032Secondary atom site location: difference Fourier map
wR(F2) = 0.190 w = 1/[σ2(Fo2) + (0.0936P)2]
where P = (Fo2 + 2Fc2)/3
S = 2.03(Δ/σ)max < 0.001
400 reflectionsΔρmax = 5.62 e Å3
1 parametersΔρmin = 3.91 e Å3
Special details top

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
U10.23800.23800.11890.001*
Si10.26040.50000.00000.007*
Al10.00000.24770.25970.003*
Si20.00000.31780.00000.007*
Si30.00000.00000.15170.007*
Al30.50000.50000.12320.003*
Al40.00000.50000.13370.003*
Geometric parameters (Å, º) top
U1—Si32.8633Si2—Si1vi2.6528
U1—Si2i2.8952Si2—Al42.7133
U1—Si22.8952Si2—Al4vi2.7133
U1—Al42.9650Si2—U1viii2.8952
U1—Al4i2.9650Si2—U1xi2.8952
U1—Si1ii2.9681Si2—U1xiii2.8952
U1—Si12.9681Si3—Al1xi2.7516
U1—Al1iii2.9937Si3—Al1xiv2.7516
U1—Al1iv2.9937Si3—Al1i2.7516
U1—Al13.0918Si3—U1i2.8633
U1—Al1i3.0918Si3—U1xi2.8633
U1—Al3v3.0937Si3—U1xiv2.8633
Si1—Si2vi2.6528Al3—Al1xv2.8549
Si1—Si22.6528Al3—Al1xvi2.8549
Si1—Si1ii2.8283Al3—Al1xii2.8549
Si1—Si1vii2.8283Al3—Al1x2.8549
Si1—Al3vi2.8786Al3—Si1xiii2.8787
Si1—Al3v2.8787Al3—Si1vi2.8787
Si1—U1viii2.9681Al3—Si1xvii2.8787
Si1—U1vii2.9681Al3—Si1xviii2.8787
Si1—U1ix2.9681Al3—U1xi3.0937
Al1—Si32.7516Al3—U1xviii3.0937
Al1—Al4iii2.7649Al3—U1xvii3.0937
Al1—Al3x2.8549Al3—U1xix3.0937
Al1—Al1i2.9243Al4—Si2vi2.7133
Al1—Al1xi2.9243Al4—Al1xii2.7649
Al1—Al42.9871Al4—Al1iii2.7649
Al1—U1xii2.9937Al4—U1xix2.9650
Al1—U1iv2.9937Al4—U1xi2.9650
Al1—Al1xii2.9958Al4—U1vii2.9650
Al1—Al1iii2.9958Al4—Al1xix2.9871
Al1—U1xi3.0918
Si3—U1—Si2i79.4U1xii—Al1—U1xi93.1
Si3—U1—Si279.4U1iv—Al1—U1xi173.0
Si2i—U1—Si280.8Al1xii—Al1—U1xi58.9
Si3—U1—Al491.8Al1iii—Al1—U1xi112.7
Si2i—U1—Al4135.9U1—Al1—U1xi80.0
Si2—U1—Al455.1Si1vi—Si2—Si1110.0
Si3—U1—Al4i91.8Si1vi—Si2—Al471.3
Si2i—U1—Al4i55.1Si1—Si2—Al471.3
Si2—U1—Al4i135.9Si1vi—Si2—Al4vi71.3
Al4—U1—Al4i168.9Si1—Si2—Al4vi71.3
Si3—U1—Si1ii133.2Al4—Si2—Al4vi111.8
Si2i—U1—Si1ii53.8Si1vi—Si2—U1viii134.0
Si2—U1—Si1ii91.5Si1—Si2—U1viii64.5
Al4—U1—Si1ii120.2Al4—Si2—U1viii134.5
Al4i—U1—Si1ii63.6Al4vi—Si2—U1viii63.7
Si3—U1—Si1133.2Si1vi—Si2—U1xi64.5
Si2i—U1—Si191.5Si1—Si2—U1xi134.0
Si2—U1—Si153.8Al4—Si2—U1xi63.7
Al4—U1—Si163.6Al4vi—Si2—U1xi134.5
Al4i—U1—Si1120.2U1viii—Si2—U1xi153.4
Si1ii—U1—Si156.9Si1vi—Si2—U1xiii64.5
Si3—U1—Al1iii113.8Si1—Si2—U1xiii134.0
Si2i—U1—Al1iii164.3Al4—Si2—U1xiii134.5
Si2—U1—Al1iii109.2Al4vi—Si2—U1xiii63.7
Al4—U1—Al1iii55.3U1viii—Si2—U1xiii86.7
Al4i—U1—Al1iii113.8U1xi—Si2—U1xiii87.3
Si1ii—U1—Al1iii112.6Si1vi—Si2—U1134.0
Si1—U1—Al1iii85.3Si1—Si2—U164.5
Si3—U1—Al1iv113.8Al4—Si2—U163.7
Si2i—U1—Al1iv109.2Al4vi—Si2—U1134.5
Si2—U1—Al1iv164.3U1viii—Si2—U187.3
Al4—U1—Al1iv113.8U1xi—Si2—U186.7
Al4i—U1—Al1iv55.3U1xiii—Si2—U1153.4
Si1ii—U1—Al1iv85.3Al1xi—Si3—Al164.2
Si1—U1—Al1iv112.6Al1xi—Si3—Al1xiv64.2
Al1iii—U1—Al1iv58.5Al1—Si3—Al1xiv97.4
Si3—U1—Al154.9Al1xi—Si3—Al1i97.4
Si2i—U1—Al1134.0Al1—Si3—Al1i64.2
Si2—U1—Al194.7Al1xiv—Si3—Al1i64.2
Al4—U1—Al159.1Al1xi—Si3—U1i130.4
Al4i—U1—Al1115.3Al1—Si3—U1i130.4
Si1ii—U1—Al1170.8Al1xiv—Si3—U1i66.8
Si1—U1—Al1122.5Al1i—Si3—U1i66.8
Al1iii—U1—Al159.0Al1xi—Si3—U1xi66.8
Al1iv—U1—Al186.9Al1—Si3—U1xi66.8
Si3—U1—Al1i54.9Al1xiv—Si3—U1xi130.4
Si2i—U1—Al1i94.7Al1i—Si3—U1xi130.4
Si2—U1—Al1i134.0U1i—Si3—U1xi157.8
Al4—U1—Al1i115.3Al1xi—Si3—U1xiv66.8
Al4i—U1—Al1i59.1Al1—Si3—U1xiv130.4
Si1ii—U1—Al1i122.5Al1xiv—Si3—U1xiv66.8
Si1—U1—Al1i170.8Al1i—Si3—U1xiv130.4
Al1iii—U1—Al1i86.9U1i—Si3—U1xiv87.9
Al1iv—U1—Al1i59.0U1xi—Si3—U1xiv87.9
Al1—U1—Al1i56.4Al1xi—Si3—U1130.4
Si3—U1—Al3v167.5Al1—Si3—U166.8
Si2i—U1—Al3v109.8Al1xiv—Si3—U1130.4
Si2—U1—Al3v109.8Al1i—Si3—U166.8
Al4—U1—Al3v87.1U1i—Si3—U187.9
Al4i—U1—Al3v87.1U1xi—Si3—U187.9
Si1ii—U1—Al3v56.7U1xiv—Si3—U1157.8
Si1—U1—Al3v56.7Al1xv—Al3—Al1xvi61.6
Al1iii—U1—Al3v55.9Al1xv—Al3—Al1xii61.6
Al1iv—U1—Al3v55.9Al1xvi—Al3—Al1xii92.8
Al1—U1—Al3v114.7Al1xv—Al3—Al1x92.8
Al1i—U1—Al3v114.7Al1xvi—Al3—Al1x61.6
Si2vi—Si1—Si270.0Al1xii—Al3—Al1x61.6
Si2vi—Si1—Si1ii170.0Al1xv—Al3—Si1xiii177.6
Si2—Si1—Si1ii100.0Al1xvi—Al3—Si1xiii119.7
Si2vi—Si1—Si1vii100.0Al1xii—Al3—Si1xiii119.7
Si2—Si1—Si1vii170.0Al1x—Al3—Si1xiii89.6
Si1ii—Si1—Si1vii90.0Al1xv—Al3—Si1vi119.7
Si2vi—Si1—Al3vi124.7Al1xvi—Al3—Si1vi177.6
Si2—Si1—Al3vi124.7Al1xii—Al3—Si1vi89.6
Si1ii—Si1—Al3vi60.6Al1x—Al3—Si1vi119.7
Si1vii—Si1—Al3vi60.6Si1xiii—Al3—Si1vi58.8
Si2vi—Si1—Al3v124.7Al1xv—Al3—Si1xvii119.7
Si2—Si1—Al3v124.7Al1xvi—Al3—Si1xvii89.6
Si1ii—Si1—Al3v60.6Al1xii—Al3—Si1xvii177.6
Si1vii—Si1—Al3v60.6Al1x—Al3—Si1xvii119.7
Al3vi—Si1—Al3v92.0Si1xiii—Al3—Si1xvii58.8
Si2vi—Si1—U1viii111.8Si1vi—Al3—Si1xvii88.0
Si2—Si1—U1viii61.7Al1xv—Al3—Si1xviii89.6
Si1ii—Si1—U1viii61.5Al1xvi—Al3—Si1xviii119.7
Si1vii—Si1—U1viii124.4Al1xii—Al3—Si1xviii119.7
Al3vi—Si1—U1viii63.9Al1x—Al3—Si1xviii177.6
Al3v—Si1—U1viii121.9Si1xiii—Al3—Si1xviii88.0
Si2vi—Si1—U1vii61.7Si1vi—Al3—Si1xviii58.8
Si2—Si1—U1vii111.8Si1xvii—Al3—Si1xviii58.8
Si1ii—Si1—U1vii124.4Al1xv—Al3—U1xi121.9
Si1vii—Si1—U1vii61.5Al1xvi—Al3—U1xi121.9
Al3vi—Si1—U1vii121.9Al1xii—Al3—U1xi60.3
Al3v—Si1—U1vii63.9Al1x—Al3—U1xi60.3
U1viii—Si1—U1vii172.8Si1xiii—Al3—U1xi59.5
Si2vi—Si1—U1111.8Si1vi—Al3—U1xi59.5
Si2—Si1—U161.7Si1xvii—Al3—U1xi118.3
Si1ii—Si1—U161.5Si1xviii—Al3—U1xi118.3
Si1vii—Si1—U1124.4Al1xv—Al3—U1xviii60.3
Al3vi—Si1—U1121.9Al1xvi—Al3—U1xviii60.3
Al3v—Si1—U163.9Al1xii—Al3—U1xviii121.9
U1viii—Si1—U184.6Al1x—Al3—U1xviii121.9
U1vii—Si1—U194.9Si1xiii—Al3—U1xviii118.3
Si2vi—Si1—U1ix61.7Si1vi—Al3—U1xviii118.3
Si2—Si1—U1ix111.8Si1xvii—Al3—U1xviii59.5
Si1ii—Si1—U1ix124.4Si1xviii—Al3—U1xviii59.5
Si1vii—Si1—U1ix61.5U1xi—Al3—U1xviii177.3
Al3vi—Si1—U1ix63.9Al1xv—Al3—U1xvii121.9
Al3v—Si1—U1ix121.9Al1xvi—Al3—U1xvii60.3
U1viii—Si1—U1ix94.9Al1xii—Al3—U1xvii121.9
U1vii—Si1—U1ix84.6Al1x—Al3—U1xvii60.3
U1—Si1—U1ix172.8Si1xiii—Al3—U1xvii59.5
Si3—Al1—Al4iii179.1Si1vi—Al3—U1xvii118.3
Si3—Al1—Al3x84.9Si1xvii—Al3—U1xvii59.5
Al4iii—Al1—Al3x96.0Si1xviii—Al3—U1xvii118.3
Si3—Al1—Al1i57.9U1xi—Al3—U1xvii90.0
Al4iii—Al1—Al1i122.6U1xviii—Al3—U1xvii90.0
Al3x—Al1—Al1i59.2Al1xv—Al3—U1xix60.3
Si3—Al1—Al1xi57.9Al1xvi—Al3—U1xix121.9
Al4iii—Al1—Al1xi122.6Al1xii—Al3—U1xix60.3
Al3x—Al1—Al1xi59.2Al1x—Al3—U1xix121.9
Al1i—Al1—Al1xi90.0Si1xiii—Al3—U1xix118.3
Si3—Al1—Al493.5Si1vi—Al3—U1xix59.5
Al4iii—Al1—Al485.6Si1xvii—Al3—U1xix118.3
Al3x—Al1—Al4178.4Si1xviii—Al3—U1xix59.5
Al1i—Al1—Al4119.9U1xi—Al3—U1xix90.0
Al1xi—Al1—Al4119.9U1xviii—Al3—U1xix90.0
Si3—Al1—U1xii118.7U1xvii—Al3—U1xix177.3
Al4iii—Al1—U1xii61.8Si2—Al4—Si2vi68.2
Al3x—Al1—U1xii63.8Si2—Al4—Al1xii122.5
Al1i—Al1—U1xii123.0Si2vi—Al4—Al1xii122.5
Al1xi—Al1—U1xii60.8Si2—Al4—Al1iii122.5
Al4—Al1—U1xii117.1Si2vi—Al4—Al1iii122.5
Si3—Al1—U1iv118.7Al1xii—Al4—Al1iii99.2
Al4iii—Al1—U1iv61.8Si2—Al4—U161.1
Al3x—Al1—U1iv63.8Si2vi—Al4—U1110.1
Al1i—Al1—U1iv60.8Al1xii—Al4—U1124.4
Al1xi—Al1—U1iv123.0Al1iii—Al4—U162.9
Al4—Al1—U1iv117.1Si2—Al4—U1xix110.1
U1xii—Al1—U1iv93.9Si2vi—Al4—U1xix61.1
Si3—Al1—Al1xii117.1Al1xii—Al4—U1xix62.9
Al4iii—Al1—Al1xii62.3Al1iii—Al4—U1xix124.4
Al3x—Al1—Al1xii125.8U1—Al4—U1xix170.4
Al1i—Al1—Al1xii173.7Si2—Al4—U1xi61.1
Al1xi—Al1—Al1xii90.0Si2vi—Al4—U1xi110.1
Al4—Al1—Al1xii55.1Al1xii—Al4—U1xi62.9
U1xii—Al1—Al1xii62.2Al1iii—Al4—U1xi124.4
U1iv—Al1—Al1xii124.0U1—Al4—U1xi84.1
Si3—Al1—Al1iii117.1U1xix—Al4—U1xi95.1
Al4iii—Al1—Al1iii62.3Si2—Al4—U1vii110.1
Al3x—Al1—Al1iii125.8Si2vi—Al4—U1vii61.1
Al1i—Al1—Al1iii90.0Al1xii—Al4—U1vii124.4
Al1xi—Al1—Al1iii173.7Al1iii—Al4—U1vii62.9
Al4—Al1—Al1iii55.1U1—Al4—U1vii95.1
U1xii—Al1—Al1iii124.0U1xix—Al4—U1vii84.1
U1iv—Al1—Al1iii62.2U1xi—Al4—U1vii170.4
Al1xii—Al1—Al1iii89.3Si2—Al4—Al1xix169.3
Si3—Al1—U158.3Si2vi—Al4—Al1xix101.1
Al4iii—Al1—U1121.1Al1xii—Al4—Al1xix62.6
Al3x—Al1—U1120.6Al1iii—Al4—Al1xix62.6
Al1i—Al1—U161.8U1—Al4—Al1xix125.4
Al1xi—Al1—U1115.8U1xix—Al4—Al1xix62.6
Al4—Al1—U158.4U1xi—Al4—Al1xix125.4
U1xii—Al1—U1173.0U1vii—Al4—Al1xix62.6
U1iv—Al1—U193.1Si2—Al4—Al1101.1
Al1xii—Al1—U1112.7Si2vi—Al4—Al1169.3
Al1iii—Al1—U158.9Al1xii—Al4—Al162.6
Si3—Al1—U1xi58.3Al1iii—Al4—Al162.6
Al4iii—Al1—U1xi121.1U1—Al4—Al162.6
Al3x—Al1—U1xi120.6U1xix—Al4—Al1125.4
Al1i—Al1—U1xi115.8U1xi—Al4—Al162.6
Al1xi—Al1—U1xi61.8U1vii—Al4—Al1125.4
Al4—Al1—U1xi58.4Al1xix—Al4—Al189.7
Symmetry codes: (i) y, x, z; (ii) y1, x, z; (iii) y1/2, x+1/2, z+1/2; (iv) x1/2, y+1/2, z+1/2; (v) x1, y, z; (vi) x, y+1, z; (vii) y, x+1, z; (viii) x, y, z; (ix) y, x+1, z; (x) x+1/2, y+1/2, z+1/2; (xi) y, x, z; (xii) y+1/2, x+1/2, z+1/2; (xiii) y, x, z; (xiv) x, y, z; (xv) x+1/2, y+1/2, z+1/2; (xvi) y+1/2, x+1/2, z+1/2; (xvii) x+1, y, z; (xviii) y+1, x+1, z; (xix) x, y+1, z.
 

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