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A new high-pressure phase of NiSi has been synthesized in a multi-anvil press by quenching samples to room temperature from 1223–1310 K at 17.5 GPa and then recovering them to atmospheric pressure. The crystal structure of this recovered material has been determined from X-ray powder diffraction data; the resulting fractional coordinates are in good agreement with those obtained from an ab initio computer simulation. The structure, in which each atom is six-fold coordinated by atoms of the other kind, is orthorhombic (space group Pmmn) with a = 3.27, b = 3.03, c = 4.70 Å. This orthorhombic phase of NiSi may be considered as a ferroelastic distortion of the hypothetical tetragonal (space group P4/nmm) NiSi structure that was predicted to be the most stable phase (at 0 K) for pressures between 23 and 61 GPa in an earlier ab initio study by Vočadlo, Wood & Dobson [J. Appl. Cryst. (2012), 45, 186–196]. Further ab initio simulations have now shown that, with increasing pressure (at 0 K), NiSi is predicted to exist in the following polymorphs: (i) the MnP structure; (ii) the new orthorhombic structure with space group Pmmn; and (iii) the CsCl structure. Experimentally, all of these structures have now been observed and, in addition, a fourth polymorph, an [epsilon]-FeSi-structured phase of NiSi (never the most thermodynamically stable phase in athermal ab initio simulations), may be readily synthesized at high pressure (P) and temperature (T). On the basis of both experiments and computer simulations it is therefore now clear that the phase diagram of NiSi at high P and T is complex. The simulated free-energy differences between different structures are often very small (<10 meV atom−1) and there is also the possibility of two displacive ferroelastic phase transformations, the first between structures with Pmmn and P4/nmm symmetry, and the second from P4/nmm to a different orthorhombic phase of NiSi with space group Pbma. A complete understanding of the NiSi phase diagram (which may be of relevance to both planetary cores and the use of thin films of NiSi in semiconductor technology) can, therefore, only come via in situ experiments at simultaneous high P and high T.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0021889812047085/ks5332sup1.cif
Contains datablocks global, XU1279_R2_overall, XU1279_R2_phase_1, XU1279_R2_phase_2, XU1279_R2_phase_3, XU1279_R2_p_01

txt

Text file https://doi.org/10.1107/S0021889812047085/ks5332sup2.txt
Data used to plot Fig 4

Computing details top

(XU1279_R2_phase_1) top
Crystal data top
Al2O3V = 254.96 (2) Å3
Mr = 101.96Z = 6
Trigonal, R3c? radiation, λ = 1.788996 Å
a = 4.7603 (3) Å?, ? × ? × ? mm
c = 12.9920 (11) Å
Data collection top
2θmin = 10.04°, 2θmax = 154.013°, 2θstep = 0.017°
Refinement top
Least-squares matrix: full8470 data points
Rp = 0.063Profile function: CW Profile function number 4 with 15 terms Pseudovoigt profile coefficients as parameterized in P. Thompson, D.E. Cox & J.B. Hastings (1987). J. Appl. Cryst.,20,79-83. Asymmetry correction of L.W. Finger, D.E. Cox & A. P. Jephcoat (1994). J. Appl. Cryst.,27,892-900. Microstrain broadening by P.W. Stephens, (1999). J. Appl. Cryst.,32,281-289. #1(GU) = 54.305 #2(GV) = 219.376 #3(GW) = -52.688 #4(GP) = 0.100 #5(LX) = 0.000 #6(ptec) = 0.00 #7(trns) = 0.00 #8(shft) = -12.6047 #9(sfec) = 0.00 #10(S/L) = 0.0220 #11(H/L) = 0.0220 #12(eta) = 1.0000 #13(S400 ) = 3.5E+00 #14(S004 ) = 1.4E-03 #15(S202 ) = -1.5E-01 #16(S301 ) = 0.0E+00 Peak tails are ignored where the intensity is below 0.0050 times the peak Aniso. broadening axis 0.0 0.0 1.0, CW Profile function number 4 with 14 terms Pseudovoigt profile coefficients as parameterized in P. Thompson, D.E. Cox & J.B. Hastings (1987). J. Appl. Cryst.,20,79-83. Asymmetry correction of L.W. Finger, D.E. Cox & A. P. Jephcoat (1994). J. Appl. Cryst.,27,892-900. Microstrain broadening by P.W. Stephens, (1999). J. Appl. Cryst.,32,281-289. #1(GU) = 79.594 #2(GV) = -80.203 #3(GW) = 25.598 #4(GP) = 0.100 #5(LX) = 1.015 #6(ptec) = 0.00 #7(trns) = 0.00 #8(shft) = -12.6047 #9(sfec) = 0.00 #10(S/L) = 0.0220 #11(H/L) = 0.0220 #12(eta) = 0.9981 #13(S400 ) = 7.9E-01 #14(S220 ) = 1.1E-01 Peak tails are ignored where the intensity is below 0.0050 times the peak Aniso. broadening axis 0.0 0.0 1.0, CW Profile function number 4 with 18 terms Pseudovoigt profile coefficients as parameterized in P. Thompson, D.E. Cox & J.B. Hastings (1987). J. Appl. Cryst.,20,79-83. Asymmetry correction of L.W. Finger, D.E. Cox & A. P. Jephcoat (1994). J. Appl. Cryst.,27,892-900. Microstrain broadening by P.W. Stephens, (1999). J. Appl. Cryst.,32,281-289. #1(GU) = 0.000 #2(GV) = 105.376 #3(GW) = -11.214 #4(GP) = 0.100 #5(LX) = 0.000 #6(ptec) = 0.00 #7(trns) = 0.00 #8(shft) = -12.6047 #9(sfec) = 0.00 #10(S/L) = 0.0220 #11(H/L) = 0.0220 #12(eta) = 0.9955 #13(S400 ) = 2.8E+02 #14(S040 ) = 5.0E+02 #15(S004 ) = 6.2E-01 #16(S220 ) = -2.2E+02 #17(S202 ) = 1.4E+01 #18(S022 ) = 7.1E+00 Peak tails are ignored where the intensity is below 0.0050 times the peak Aniso. broadening axis 0.0 0.0 1.0
Rwp = 0.08748 parameters
Rexp = 0.0350 restraints
R(F2) = 0.03692(Δ/σ)max = 0.02
χ2 = 6.350Background function: GSAS Background function number 1 with 10 terms. Shifted Chebyshev function of 1st kind 1: 561.830 2: -452.611 3: 272.417 4: -148.634 5: 93.9376 6: -81.8660 7: 65.6109 8: -32.8739 9: 24.8376 10: -14.2220
Crystal data top
Al2O3V = 254.96 (2) Å3
Mr = 101.96Z = 6
Trigonal, R3c? radiation, λ = 1.788996 Å
a = 4.7603 (3) Å?, ? × ? × ? mm
c = 12.9920 (11) Å
Data collection top
2θmin = 10.04°, 2θmax = 154.013°, 2θstep = 0.017°
Refinement top
Rp = 0.063χ2 = 6.350
Rwp = 0.0878470 data points
Rexp = 0.03548 parameters
R(F2) = 0.036920 restraints
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
Al0.00.00.352190.00337
O0.693690.00.250.00367
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Al0.003380.003380.003350.001690.00.0
O0.003590.003320.003940.001610.00350.007
Geometric parameters (Å, º) top
Al—Ali2.6553 (2)Al—Oviii1.8548 (1)
Al—Alii2.7917 (2)Al—Oix1.8548 (1)
Al—Aliii2.7917 (2)Al—Ox1.8548 (1)
Al—Aliv2.7917 (2)O—Alxi1.9720 (1)
Al—Ov1.9720 (1)O—Alxii1.9720 (1)
Al—Ovi1.9720 (1)O—Aliii1.8548 (1)
Al—Ovii1.9720 (1)O—Alxiii1.8548 (1)
Ali—Al—Aliv79.8916 (11)Alxv—Al—Ovii41.5328 (12)
Ali—Al—Alxiv79.8916 (11)Alxv—Al—Oxvi143.9647 (3)
Ali—Al—Alxv79.8916 (11)Alxv—Al—Oxvii97.9548 (8)
Ali—Al—Ov47.682 (3)Alxv—Al—Oxviii44.826 (3)
Ali—Al—Ovi47.682 (3)Ov—Al—Ovi79.636 (5)
Ali—Al—Ovii47.682 (3)Ov—Al—Ovii79.636 (5)
Ali—Al—Oxvi116.849 (3)Ov—Al—Oxvi86.359 (4)
Ali—Al—Oxvii116.849 (3)Ov—Al—Oxvii164.2123 (6)
Ali—Al—Oxviii116.849 (3)Ov—Al—Oxviii90.769 (4)
Aliv—Al—Alxiv116.9874 (7)Ovi—Al—Ovii79.636 (5)
Aliv—Al—Alxv116.9874 (7)Ovi—Al—Oxvi90.769 (4)
Aliv—Al—Ov41.5328 (12)Ovi—Al—Oxvii86.359 (4)
Aliv—Al—Ovi83.2140 (12)Ovi—Al—Oxviii164.2123 (6)
Aliv—Al—Ovii120.814 (4)Ovii—Al—Oxvi164.2122 (6)
Aliv—Al—Oxvi44.826 (3)Ovii—Al—Oxvii90.769 (4)
Aliv—Al—Oxvii143.9648 (3)Ovii—Al—Oxviii86.359 (4)
Aliv—Al—Oxviii97.9548 (8)Oxvi—Al—Oxvii101.188 (3)
Alxiv—Al—Alxv116.9874 (7)Oxvi—Al—Oxviii101.188 (3)
Alxiv—Al—Ov120.814 (4)Oxvii—Al—Oxviii101.188 (3)
Alxiv—Al—Ovi41.5328 (12)Alxi—O—Alxii84.636 (7)
Alxiv—Al—Ovii83.2140 (12)Alxi—O—Alxiv93.641 (4)
Alxiv—Al—Oxvi97.9548 (8)Alxi—O—Alxiii132.1928 (15)
Alxiv—Al—Oxvii44.826 (3)Alxii—O—Alxiv132.1928 (15)
Alxiv—Al—Oxviii143.9648 (3)Alxii—O—Alxiii93.641 (4)
Alxv—Al—Ov83.2140 (12)Alxiv—O—Alxiii120.3833 (15)
Alxv—Al—Ovi120.814 (4)
Symmetry codes: (i) xy, y, z+1/2; (ii) x4/3, y5/3, z2/3; (iii) x1/3, y5/3, z2/3; (iv) x1/3, y2/3, z2/3; (v) x1, y, z; (vi) y, xy1, z; (vii) yx+1, x+1, z; (viii) yx+1/3, y1/3, z+1/6; (ix) y+1/3, x+2/3, z+1/6; (x) x2/3, xy1/3, z+1/6; (xi) x+1, y, z; (xii) xy+1, y, z+1/2; (xiii) yx+2/3, y+1/3, z1/6; (xiv) x+2/3, y2/3, z2/3; (xv) x+2/3, y+1/3, z2/3; (xvi) yx+1/3, y1/3, z11/6; (xvii) y+1/3, x+2/3, z11/6; (xviii) x2/3, xy1/3, z11/6.
(XU1279_R2_phase_2) top
Crystal data top
NiSiV = 90.93 (1) Å3
Mr = 86.79Z = 4
Cubic, P213? radiation, λ = 1.788996 Å
a = 4.49678 (5) Å?, ? × ? × ? mm
Data collection top
2θmin = 10.04°, 2θmax = 154.013°, 2θstep = 0.017°
Refinement top
Least-squares matrix: full8470 data points
Rp = 0.063Profile function: CW Profile function number 4 with 15 terms Pseudovoigt profile coefficients as parameterized in P. Thompson, D.E. Cox & J.B. Hastings (1987). J. Appl. Cryst.,20,79-83. Asymmetry correction of L.W. Finger, D.E. Cox & A. P. Jephcoat (1994). J. Appl. Cryst.,27,892-900. Microstrain broadening by P.W. Stephens, (1999). J. Appl. Cryst.,32,281-289. #1(GU) = 54.305 #2(GV) = 219.376 #3(GW) = -52.688 #4(GP) = 0.100 #5(LX) = 0.000 #6(ptec) = 0.00 #7(trns) = 0.00 #8(shft) = -12.6047 #9(sfec) = 0.00 #10(S/L) = 0.0220 #11(H/L) = 0.0220 #12(eta) = 1.0000 #13(S400 ) = 3.5E+00 #14(S004 ) = 1.4E-03 #15(S202 ) = -1.5E-01 #16(S301 ) = 0.0E+00 Peak tails are ignored where the intensity is below 0.0050 times the peak Aniso. broadening axis 0.0 0.0 1.0, CW Profile function number 4 with 14 terms Pseudovoigt profile coefficients as parameterized in P. Thompson, D.E. Cox & J.B. Hastings (1987). J. Appl. Cryst.,20,79-83. Asymmetry correction of L.W. Finger, D.E. Cox & A. P. Jephcoat (1994). J. Appl. Cryst.,27,892-900. Microstrain broadening by P.W. Stephens, (1999). J. Appl. Cryst.,32,281-289. #1(GU) = 79.594 #2(GV) = -80.203 #3(GW) = 25.598 #4(GP) = 0.100 #5(LX) = 1.015 #6(ptec) = 0.00 #7(trns) = 0.00 #8(shft) = -12.6047 #9(sfec) = 0.00 #10(S/L) = 0.0220 #11(H/L) = 0.0220 #12(eta) = 0.9981 #13(S400 ) = 7.9E-01 #14(S220 ) = 1.1E-01 Peak tails are ignored where the intensity is below 0.0050 times the peak Aniso. broadening axis 0.0 0.0 1.0, CW Profile function number 4 with 18 terms Pseudovoigt profile coefficients as parameterized in P. Thompson, D.E. Cox & J.B. Hastings (1987). J. Appl. Cryst.,20,79-83. Asymmetry correction of L.W. Finger, D.E. Cox & A. P. Jephcoat (1994). J. Appl. Cryst.,27,892-900. Microstrain broadening by P.W. Stephens, (1999). J. Appl. Cryst.,32,281-289. #1(GU) = 0.000 #2(GV) = 105.376 #3(GW) = -11.214 #4(GP) = 0.100 #5(LX) = 0.000 #6(ptec) = 0.00 #7(trns) = 0.00 #8(shft) = -12.6047 #9(sfec) = 0.00 #10(S/L) = 0.0220 #11(H/L) = 0.0220 #12(eta) = 0.9955 #13(S400 ) = 2.8E+02 #14(S040 ) = 5.0E+02 #15(S004 ) = 6.2E-01 #16(S220 ) = -2.2E+02 #17(S202 ) = 1.4E+01 #18(S022 ) = 7.1E+00 Peak tails are ignored where the intensity is below 0.0050 times the peak Aniso. broadening axis 0.0 0.0 1.0
Rwp = 0.08748 parameters
Rexp = 0.0350 restraints
R(F2) = 0.03692(Δ/σ)max = 0.02
χ2 = 6.350Background function: GSAS Background function number 1 with 10 terms. Shifted Chebyshev function of 1st kind 1: 561.830 2: -452.611 3: 272.417 4: -148.634 5: 93.9376 6: -81.8660 7: 65.6109 8: -32.8739 9: 24.8376 10: -14.2220
Crystal data top
NiSiV = 90.93 (1) Å3
Mr = 86.79Z = 4
Cubic, P213? radiation, λ = 1.788996 Å
a = 4.49678 (5) Å?, ? × ? × ? mm
Data collection top
2θmin = 10.04°, 2θmax = 154.013°, 2θstep = 0.017°
Refinement top
Rp = 0.063χ2 = 6.350
Rwp = 0.0878470 data points
Rexp = 0.03548 parameters
R(F2) = 0.036920 restraints
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
Ni10.1470 (9)0.1470 (9)0.1470 (9)0.0167 (16)*
Si10.1399 (12)0.1399 (12)0.1399 (12)0.0167 (16)*
Geometric parameters (Å, º) top
Ni1—Ni1i2.7679 (12)Si1—Ni12.234 (9)
Ni1—Ni1ii2.7679 (12)Si1—Ni1x2.474 (8)
Ni1—Ni1iii2.7679 (12)Si1—Ni1i2.415 (7)
Ni1—Ni1iv2.7679 (12)Si1—Ni1xi2.474 (8)
Ni1—Ni1v2.7679 (12)Si1—Ni1iii2.415 (7)
Ni1—Ni1vi2.7679 (12)Si1—Ni1xii2.474 (8)
Ni1—Si12.234 (9)Si1—Ni1v2.415 (7)
Ni1—Si1vii2.474 (8)Si1—Si1x2.7602 (10)
Ni1—Si1ii2.415 (7)Si1—Si1vii2.7602 (10)
Ni1—Si1viii2.474 (8)Si1—Si1xi2.7602 (10)
Ni1—Si1iv2.415 (7)Si1—Si1viii2.7602 (10)
Ni1—Si1ix2.474 (8)Si1—Si1xii2.7602 (10)
Ni1—Si1vi2.415 (7)Si1—Si1ix2.7602 (10)
Si1—Ni1—Si1vii71.58 (16)Ni1—Si1—Ni1x139.76 (14)
Si1—Ni1—Si1ii138.71 (13)Ni1—Si1—Ni1i73.0 (2)
Si1—Ni1—Si1viii71.58 (16)Ni1—Si1—Ni1xi139.76 (14)
Si1—Ni1—Si1iv138.71 (13)Ni1—Si1—Ni1iii73.0 (2)
Si1—Ni1—Si1ix71.58 (16)Ni1—Si1—Ni1xii139.76 (14)
Si1—Ni1—Si1vi138.71 (13)Ni1—Si1—Ni1v73.0 (2)
Si1vii—Ni1—Si1ii133.8 (2)Ni1x—Si1—Ni1i133.8 (2)
Si1vii—Ni1—Si1viii110.50 (15)Ni1x—Si1—Ni1xi68.0 (2)
Si1vii—Ni1—Si1iv112.5 (4)Ni1x—Si1—Ni1iii68.96 (9)
Si1vii—Ni1—Si1ix110.50 (15)Ni1x—Si1—Ni1xii68.0 (2)
Si1vii—Ni1—Si1vi68.74 (10)Ni1x—Si1—Ni1v109.8 (3)
Si1ii—Ni1—Si1viii68.74 (10)Ni1i—Si1—Ni1xi109.8 (3)
Si1ii—Ni1—Si1iv69.7 (2)Ni1i—Si1—Ni1iii111.79 (19)
Si1ii—Ni1—Si1ix112.5 (4)Ni1i—Si1—Ni1xii68.96 (9)
Si1ii—Ni1—Si1vi69.7 (2)Ni1i—Si1—Ni1v111.79 (19)
Si1viii—Ni1—Si1iv133.8 (2)Ni1xi—Si1—Ni1iii133.8 (2)
Si1viii—Ni1—Si1ix110.50 (15)Ni1xi—Si1—Ni1xii68.0 (2)
Si1viii—Ni1—Si1vi112.5 (4)Ni1xi—Si1—Ni1v68.96 (9)
Si1iv—Ni1—Si1ix68.74 (10)Ni1iii—Si1—Ni1xii109.8 (3)
Si1iv—Ni1—Si1vi69.7 (2)Ni1iii—Si1—Ni1v111.79 (19)
Si1ix—Ni1—Si1vi133.8 (2)Ni1xii—Si1—Ni1v133.8 (2)
Symmetry codes: (i) x1/2, y+1/2, z; (ii) x+1/2, y+1/2, z; (iii) z, x1/2, y+1/2; (iv) z, x+1/2, y+1/2; (v) y+1/2, z, x1/2; (vi) y+1/2, z, x+1/2; (vii) x+1/2, y1/2, z; (viii) z, x+1/2, y1/2; (ix) y1/2, z, x+1/2; (x) x1/2, y1/2, z; (xi) z, x1/2, y1/2; (xii) y1/2, z, x1/2.
(XU1279_R2_phase_3) top
Crystal data top
NiSic = 4.69776 (6) Å
Mr = 86.79V = 46.54 (1) Å3
Orthorhombic, PmmnZ = 2
a = 3.27350 (15) Å? radiation, λ = 1.788996 Å
b = 3.02662 (12) Å?, ? × ? × ? mm
Data collection top
2θmin = 10.04°, 2θmax = 154.013°, 2θstep = 0.017°
Refinement top
Least-squares matrix: full8470 data points
Rp = 0.063Profile function: CW Profile function number 4 with 15 terms Pseudovoigt profile coefficients as parameterized in P. Thompson, D.E. Cox & J.B. Hastings (1987). J. Appl. Cryst.,20,79-83. Asymmetry correction of L.W. Finger, D.E. Cox & A. P. Jephcoat (1994). J. Appl. Cryst.,27,892-900. Microstrain broadening by P.W. Stephens, (1999). J. Appl. Cryst.,32,281-289. #1(GU) = 54.305 #2(GV) = 219.376 #3(GW) = -52.688 #4(GP) = 0.100 #5(LX) = 0.000 #6(ptec) = 0.00 #7(trns) = 0.00 #8(shft) = -12.6047 #9(sfec) = 0.00 #10(S/L) = 0.0220 #11(H/L) = 0.0220 #12(eta) = 1.0000 #13(S400 ) = 3.5E+00 #14(S004 ) = 1.4E-03 #15(S202 ) = -1.5E-01 #16(S301 ) = 0.0E+00 Peak tails are ignored where the intensity is below 0.0050 times the peak Aniso. broadening axis 0.0 0.0 1.0, CW Profile function number 4 with 14 terms Pseudovoigt profile coefficients as parameterized in P. Thompson, D.E. Cox & J.B. Hastings (1987). J. Appl. Cryst.,20,79-83. Asymmetry correction of L.W. Finger, D.E. Cox & A. P. Jephcoat (1994). J. Appl. Cryst.,27,892-900. Microstrain broadening by P.W. Stephens, (1999). J. Appl. Cryst.,32,281-289. #1(GU) = 79.594 #2(GV) = -80.203 #3(GW) = 25.598 #4(GP) = 0.100 #5(LX) = 1.015 #6(ptec) = 0.00 #7(trns) = 0.00 #8(shft) = -12.6047 #9(sfec) = 0.00 #10(S/L) = 0.0220 #11(H/L) = 0.0220 #12(eta) = 0.9981 #13(S400 ) = 7.9E-01 #14(S220 ) = 1.1E-01 Peak tails are ignored where the intensity is below 0.0050 times the peak Aniso. broadening axis 0.0 0.0 1.0, CW Profile function number 4 with 18 terms Pseudovoigt profile coefficients as parameterized in P. Thompson, D.E. Cox & J.B. Hastings (1987). J. Appl. Cryst.,20,79-83. Asymmetry correction of L.W. Finger, D.E. Cox & A. P. Jephcoat (1994). J. Appl. Cryst.,27,892-900. Microstrain broadening by P.W. Stephens, (1999). J. Appl. Cryst.,32,281-289. #1(GU) = 0.000 #2(GV) = 105.376 #3(GW) = -11.214 #4(GP) = 0.100 #5(LX) = 0.000 #6(ptec) = 0.00 #7(trns) = 0.00 #8(shft) = -12.6047 #9(sfec) = 0.00 #10(S/L) = 0.0220 #11(H/L) = 0.0220 #12(eta) = 0.9955 #13(S400 ) = 2.8E+02 #14(S040 ) = 5.0E+02 #15(S004 ) = 6.2E-01 #16(S220 ) = -2.2E+02 #17(S202 ) = 1.4E+01 #18(S022 ) = 7.1E+00 Peak tails are ignored where the intensity is below 0.0050 times the peak Aniso. broadening axis 0.0 0.0 1.0
Rwp = 0.08748 parameters
Rexp = 0.0350 restraints
R(F2) = 0.03692(Δ/σ)max = 0.02
χ2 = 6.350Background function: GSAS Background function number 1 with 10 terms. Shifted Chebyshev function of 1st kind 1: 561.830 2: -452.611 3: 272.417 4: -148.634 5: 93.9376 6: -81.8660 7: 65.6109 8: -32.8739 9: 24.8376 10: -14.2220
Crystal data top
NiSic = 4.69776 (6) Å
Mr = 86.79V = 46.54 (1) Å3
Orthorhombic, PmmnZ = 2
a = 3.27350 (15) Å? radiation, λ = 1.788996 Å
b = 3.02662 (12) Å?, ? × ? × ? mm
Data collection top
2θmin = 10.04°, 2θmax = 154.013°, 2θstep = 0.017°
Refinement top
Rp = 0.063χ2 = 6.350
Rwp = 0.0878470 data points
Rexp = 0.03548 parameters
R(F2) = 0.036920 restraints
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
NI10.250.250.34422 (19)0.0200 (9)*
SI20.250.250.8423 (9)0.0200 (9)*
Geometric parameters (Å, º) top
NI1—NI1i3.2735 (2)SI2—NI12.340 (4)
NI1—NI1ii3.0266 (1)SI2—NI1x2.358 (4)
NI1—NI1iii3.0266 (1)SI2—NI1v2.3951 (14)
NI1—NI1iv3.2735 (2)SI2—NI1vi2.3951 (14)
NI1—NI1v2.6667 (10)SI2—NI1vii2.3951 (14)
NI1—NI1vi2.6667 (10)SI2—NI1viii2.3951 (14)
NI1—NI1vii2.6667 (10)SI2—SI2i3.2735 (2)
NI1—NI1viii2.6667 (10)SI2—SI2ii3.0266 (1)
NI1—SI2ix2.358 (4)SI2—SI2iii3.0266 (1)
NI1—SI22.340 (4)SI2—SI2iv3.2735 (2)
NI1—SI2v2.3951 (14)SI2—SI2xi2.677 (4)
NI1—SI2vi2.3951 (14)SI2—SI2xii2.677 (4)
NI1—SI2vii2.3951 (14)SI2—SI2xiii2.677 (4)
NI1—SI2viii2.3951 (14)SI2—SI2xiv2.677 (4)
SI2ix—NI1—SI2180.0NI1—SI2—NI1x180.0
SI2ix—NI1—SI2v68.54 (8)NI1—SI2—NI1v68.54 (8)
SI2ix—NI1—SI2vi68.54 (8)NI1—SI2—NI1vi68.54 (8)
SI2ix—NI1—SI2vii68.54 (8)NI1—SI2—NI1vii68.54 (8)
SI2ix—NI1—SI2viii68.54 (8)NI1—SI2—NI1viii68.54 (8)
SI2—NI1—SI2v111.46 (8)NI1x—SI2—NI1v111.46 (8)
SI2—NI1—SI2vi111.46 (8)NI1x—SI2—NI1vi111.46 (8)
SI2—NI1—SI2vii111.46 (8)NI1x—SI2—NI1vii111.46 (8)
SI2—NI1—SI2viii111.46 (8)NI1x—SI2—NI1viii111.46 (8)
SI2v—NI1—SI2vi78.37 (5)NI1v—SI2—NI1vi78.37 (5)
SI2v—NI1—SI2vii86.22 (6)NI1v—SI2—NI1vii86.22 (6)
SI2v—NI1—SI2viii137.09 (17)NI1v—SI2—NI1viii137.09 (17)
SI2vi—NI1—SI2vii137.09 (17)NI1vi—SI2—NI1vii137.09 (17)
SI2vi—NI1—SI2viii86.22 (6)NI1vi—SI2—NI1viii86.22 (6)
SI2vii—NI1—SI2viii78.37 (5)NI1vii—SI2—NI1viii78.37 (5)
Symmetry codes: (i) x1, y, z; (ii) x, y1, z; (iii) x, y+1, z; (iv) x+1, y, z; (v) x, y, z+1; (vi) x, y+1, z+1; (vii) x+1, y, z+1; (viii) x+1, y+1, z+1; (ix) x, y, z1; (x) x, y, z+1; (xi) x, y, z+2; (xii) x, y+1, z+2; (xiii) x+1, y, z+2; (xiv) x+1, y+1, z+2.

Experimental details

(XU1279_R2_phase_1)(XU1279_R2_phase_2)(XU1279_R2_phase_3)
Crystal data
Chemical formulaAl2O3NiSiNiSi
Mr101.9686.7986.79
Crystal system, space groupTrigonal, R3cCubic, P213Orthorhombic, Pmmn
Temperature (K)???
a, b, c (Å)4.7603 (3), 4.76029, 12.9920 (11)4.49678 (5), 4.49678, 4.496783.27350 (15), 3.02662 (12), 4.69776 (6)
α, β, γ (°)90, 90, 12090, 90, 9090, 90, 90
V3)254.96 (2)90.93 (1)46.54 (1)
Z642
Radiation type?, λ = 1.788996 Å?, λ = 1.788996 Å?, λ = 1.788996 Å
Specimen shape, size (mm)?, ? × ? × ??, ? × ? × ??, ? × ? × ?
Data collection
Diffractometer???
Specimen mounting???
Data collection mode???
Scan method???
2θ values (°)2θmin = 10.04 2θmax = 154.013 2θstep = 0.0172θmin = 10.04 2θmax = 154.013 2θstep = 0.0172θmin = 10.04 2θmax = 154.013 2θstep = 0.017
Refinement
R factors and goodness of fitRp = 0.063, Rwp = 0.087, Rexp = 0.035, R(F2) = 0.03692, χ2 = 6.350Rp = 0.063, Rwp = 0.087, Rexp = 0.035, R(F2) = 0.03692, χ2 = 6.350Rp = 0.063, Rwp = 0.087, Rexp = 0.035, R(F2) = 0.03692, χ2 = 6.350
No. of data points847084708470
No. of parameters484848

Computer programs: GSAS.

 

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