Synchrotron X-ray and ab initio studies of β-Si3N4

du Boulay, D.; Ishizawa, N.; Atake, T.; Streltsov, V.; Furuya, K.; Munakata, F.

doi:10.1107/S010876810401393X

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Synchrotron X-ray and ab initio studies of β-Si₃N₄

D. du Boulay, N. Ishizawa, T. Atake, V. Streltsov, K. Furuya and F. Munakata

Almost absorption- and extinction-free single-crystal synchrotron X-ray diffraction data were measured at 150, 200 and 295 K for β-Si₃N₄, silicon nitride, at a wavelength of 0.7 Å. The true symmetry of this material has been the subject of minor controversy for several decades. No compelling evidence favouring the low-symmetry P6₃ model was identified in this study.

Keywords: synchrotron X-ray diffraction; ceramic.

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Supporting information

	Crystallographic Information File (CIF) https://doi.org/10.1107/S010876810401393X/av5009sup1.cif Contains datablocks 295K-C, 295K-N, 200K-C, 200K-N, 150K-C, 150K-N
	Structure factor file (CIF format) https://doi.org/10.1107/S010876810401393X/av5009295K-Csup2.hkl Contains datablock 295K-C
	Structure factor file (CIF format) https://doi.org/10.1107/S010876810401393X/av5009200K-Csup3.hkl Contains datablock 200K-C
	Structure factor file (CIF format) https://doi.org/10.1107/S010876810401393X/av5009150K-Csup4.hkl Contains datablock 150K-C

Computing details top

For all compounds, data collection: Diff14A, Vaalsta & Hester 1997; cell refinement: Xtal3.7 LATCON; data reduction: Xtal DIFDAT SORTRF ABSORB ADDREF; program(s) used to solve structure: already known structure; program(s) used to refine structure: Xtal CRYLSQ; molecular graphics: Xtal; software used to prepare material for publication: Xtal BONDLA CIFIO.

Figures top

(295K-C) top

Crystal data top

N₄Si₃	D_x = 3.202 Mg m⁻³
M_r = 140.31	Syn x radiation, λ = 0.75022 Å
Hexagonal, P6₃/m	Cell parameters from 21 reflections
Hall symbol: -p 6c	θ = 45.8–63.9°
a = 7.6044 (1) Å	µ = 1.53 mm⁻¹
c = 2.9063 (1) Å	T = 295 K
V = 145.55 (1) Å³	Spheroid, colourless
Z = 1.5	0.08 × 0.08 × 0.08 × 0.04 (radius) mm
F(000) = 140

Data collection top

PF-BL14A Rigaku 4circle diffractometer	792 reflections with F > .00 sig(F )
Radiation source: Synchrotron	R_int = 0.025
Double Si monochromator	θ_max = 65.0°, θ_min = 3.3°
%w/2%q scans	h = −18→18
Absorption correction: for a sphere ?	k = −18→18
T_min = 0.939, T_max = 0.940	l = −7→7
8577 measured reflections	6 standard reflections every 100 reflections
800 independent reflections	intensity decay: none

Refinement top

Refinement on F	0 constraints
Least-squares matrix: full	Weighting scheme based on measured s.u.'s
R[F² > 2σ(F²)] = 0.020	(Δ/σ)_max = 0.00029
wR(F²) = 0.015	Δρ_max = 0.61 e Å⁻³
S = 2.01	Δρ_min = −0.53 e Å⁻³
796 reflections	Extinction correction: Zachariasen, Eq22 p292 "Cryst. Comp." Munksgaard 1970
16 parameters	Extinction coefficient: 1587 (307)
0 restraints	Absolute structure: see text

Crystal data top

N₄Si₃	Z = 1.5
M_r = 140.31	Syn x radiation, λ = 0.75022 Å
Hexagonal, P6₃/m	µ = 1.53 mm⁻¹
a = 7.6044 (1) Å	T = 295 K
c = 2.9063 (1) Å	0.08 × 0.08 × 0.08 × 0.04 (radius) mm
V = 145.55 (1) Å³

Data collection top

PF-BL14A Rigaku 4circle diffractometer	792 reflections with F > .00 sig(F )
Absorption correction: for a sphere ?	R_int = 0.025
T_min = 0.939, T_max = 0.940	6 standard reflections every 100 reflections
8577 measured reflections	intensity decay: none
800 independent reflections

Refinement top

R[F² > 2σ(F²)] = 0.020	0 restraints
wR(F²) = 0.015	Δρ_max = 0.61 e Å⁻³
S = 2.01	Δρ_min = −0.53 e Å⁻³
796 reflections	Absolute structure: see text
16 parameters

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

	x	y	z	U_iso*/U_eq
Si	0.768477 (16)	0.174557 (15)	0.25000	0.00293 (3)
N1	0.03050 (4)	0.33024 (4)	0.25000	0.00413 (6)
N2	0.66666	0.33333	0.25000	0.00398 (9)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Si	0.00312 (3)	0.00284 (3)	0.00270 (3)	0.00139 (3)	0.00000	0.00000
N1	0.00312 (7)	0.00548 (7)	0.00297 (7)	0.00153 (6)	0.00000	0.00000
N2	0.00332 (7)	0.00332 (7)	0.00530 (12)	0.00166 (4)	0.00000	0.00000

Geometric parameters (Å, º) top

Si—N2	1.7298 (1)	Si—N1	1.7357 (2)
Si—N1	1.7357 (3)	Si—N1	1.7357 (2)

N2—Si—N1	106.602 (13)	Si—N1—Si	123.038 (8)
N2—Si—N1	110.103 (13)	Si—N1—Si	123.038 (8)
N2—Si—N1	110.103 (13)	Si—N1—Si	113.697 (15)
N1—Si—N1	108.024 (12)	Si—N2—Si	119.998 (6)
N1—Si—N1	108.024 (12)	Si—N2—Si	120.002 (5)
N1—Si—N1	113.697 (12)	Si—N2—Si	120.001 (7)

(295K-N) top

Crystal data top

N₄Si₃	D_x = 3.202 Mg m⁻³
M_r = 140.31	Syn x radiation, λ = 0.75022 Å
Hexagonal, P6₃	Cell parameters from 21 reflections
Hall symbol: p 6c	θ = 45.8–63.9°
a = 7.6044 (1) Å	µ = 1.53 mm⁻¹
c = 2.9063 (1) Å	T = 295 K
V = 145.55 (1) Å³	Spheroid, colourless
Z = 1.5	0.08 × 0.08 × 0.08 × 0.04 (radius) mm
F(000) = 140

Data collection top

PF-BL14A Rigaku 4circle diffractometer	792 reflections with F > .00 sig(F )
Radiation source: Synchrotron	R_int = 0.025
Double Si monochromator	θ_max = 65.0°, θ_min = 3.3°
%w/2%q scans	h = −18→18
Absorption correction: for a sphere ?	k = −18→18
T_min = 0.939, T_max = 0.940	l = −7→7
8577 measured reflections	6 standard reflections every 100 reflections
800 independent reflections	intensity decay: none

Refinement top

Refinement on F	0 constraints
Least-squares matrix: full	Weighting scheme based on measured s.u.'s
R[F² > 2σ(F²)] = 0.018	(Δ/σ)_max = 0.001
wR(F²) = 0.014	Δρ_max = 0.53 e Å⁻³
S = 1.88	Δρ_min = −0.48 e Å⁻³
796 reflections	Extinction correction: Zachariasen, Eq22 p292 "Cryst. Comp." Munksgaard 1970
22 parameters	Extinction coefficient: 2099 (391)
0 restraints	Absolute structure: see text

Crystal data top

N₄Si₃	Z = 1.5
M_r = 140.31	Syn x radiation, λ = 0.75022 Å
Hexagonal, P6₃	µ = 1.53 mm⁻¹
a = 7.6044 (1) Å	T = 295 K
c = 2.9063 (1) Å	0.08 × 0.08 × 0.08 × 0.04 (radius) mm
V = 145.55 (1) Å³

Data collection top

PF-BL14A Rigaku 4circle diffractometer	792 reflections with F > .00 sig(F )
Absorption correction: for a sphere ?	R_int = 0.025
T_min = 0.939, T_max = 0.940	6 standard reflections every 100 reflections
8577 measured reflections	intensity decay: none
800 independent reflections

Refinement top

R[F² > 2σ(F²)] = 0.018	0 restraints
wR(F²) = 0.014	Δρ_max = 0.53 e Å⁻³
S = 1.88	Δρ_min = −0.48 e Å⁻³
796 reflections	Absolute structure: see text
22 parameters

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

	x	y	z	U_iso*/U_eq
Si	0.768473 (15)	0.174555 (15)	0.25000	0.00299 (3)
N1	0.03055 (4)	0.33028 (4)	0.2487 (6)	0.00418 (6)
N2	0.66666	0.33333	0.2515 (11)	0.00401 (8)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Si	0.00316 (3)	0.00289 (3)	0.00278 (3)	0.00142 (2)	0.00135 (11)	0.00108 (11)
N1	0.00311 (6)	0.00553 (7)	0.00304 (7)	0.00151 (6)	−0.0011 (3)	−0.0007 (3)
N2	0.00334 (7)	0.00334 (7)	0.00534 (12)	0.00167 (3)	0.00000	0.00000

Geometric parameters (Å, º) top

Si—N2	1.7297 (1)	Si—N1	1.7387 (14)
Si—N1	1.7361 (3)	Si—N1	1.7323 (14)

N2—Si—N1	106.601 (14)	Si—N1—Si	123.22 (8)
N2—Si—N1	110.19 (10)	Si—N1—Si	122.83 (8)
N2—Si—N1	110.00 (10)	Si—N1—Si	113.716 (15)
N1—Si—N1	107.88 (5)	Si—N2—Si	119.997 (4)
N1—Si—N1	108.17 (5)	Si—N2—Si	120.001 (4)
N1—Si—N1	113.72 (4)	Si—N2—Si	120.000 (6)

(200K-C) top

Crystal data top

N₄Si₃	D_x = 3.204 Mg m⁻³
M_r = 140.31	Syn x radiation, λ = 0.75037 Å
Hexagonal, P6₃/m	Cell parameters from 12 reflections
Hall symbol: -p 6c	θ = 52.4–56.0°
a = 7.6015 (3) Å	µ = 1.54 mm⁻¹
c = 2.9061 (1) Å	T = 200 K
V = 145.43 (1) Å³	Irregular, colourless
Z = 1.5	0.04 × 0.03 × 0.02 mm
F(000) = 140

Data collection top

PF-BL14A Rigaku 4circle diffractometer	852 reflections with F > .00 sig(F )
Radiation source: Synchrotron	R_int = 0.028
Double Si monochromator	θ_max = 68.9°, θ_min = 3.3°
%w/2%q scans	h = −18→18
Absorption correction: analytical ?	k = −18→18
T_min = 0.932, T_max = 0.972	l = −7→7
12331 measured reflections	6 standard reflections every 200 reflections
866 independent reflections	intensity decay: none

Refinement top

Refinement on F	0 constraints
Least-squares matrix: full	Weighting scheme based on measured s.u.'s
R[F² > 2σ(F²)] = 0.014	(Δ/σ)_max = 0.001
wR(F²) = 0.011	Δρ_max = 0.45 e Å⁻³
S = 1.89	Δρ_min = −0.37 e Å⁻³
866 reflections	Extinction correction: Zachariasen, Eq22 p292 "Cryst. Comp." Munksgaard 1970
16 parameters	Extinction coefficient: 1296 (439)
0 restraints	Absolute structure: see text

Crystal data top

N₄Si₃	Z = 1.5
M_r = 140.31	Syn x radiation, λ = 0.75037 Å
Hexagonal, P6₃/m	µ = 1.54 mm⁻¹
a = 7.6015 (3) Å	T = 200 K
c = 2.9061 (1) Å	0.04 × 0.03 × 0.02 mm
V = 145.43 (1) Å³

Data collection top

PF-BL14A Rigaku 4circle diffractometer	852 reflections with F > .00 sig(F )
Absorption correction: analytical ?	R_int = 0.028
T_min = 0.932, T_max = 0.972	6 standard reflections every 200 reflections
12331 measured reflections	intensity decay: none
866 independent reflections

Refinement top

R[F² > 2σ(F²)] = 0.014	0 restraints
wR(F²) = 0.011	Δρ_max = 0.45 e Å⁻³
S = 1.89	Δρ_min = −0.37 e Å⁻³
866 reflections	Absolute structure: see text
16 parameters

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

	x	y	z	U_iso*/U_eq
Si	0.768477 (9)	0.174569 (9)	0.25000	0.00286 (2)
N1	0.03049 (2)	0.33026 (3)	0.25000	0.00393 (4)
N2	0.66666	0.33333	0.25000	0.00382 (5)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Si	0.00313 (2)	0.00294 (2)	0.00243 (3)	0.001459 (16)	0.00000	0.00000
N1	0.00322 (4)	0.00502 (4)	0.00283 (4)	0.00153 (3)	0.00000	0.00000
N2	0.00342 (4)	0.00342 (4)	0.00464 (8)	0.00171 (2)	0.00000	0.00000

Geometric parameters (Å, º) top

Si—N2	1.7290 (1)	Si—N1	1.7354 (1)
Si—N1	1.7351 (2)	Si—N1	1.7354 (1)

N2—Si—N1	106.600 (9)	Si—N1—Si	123.032 (5)
N2—Si—N1	110.096 (8)	Si—N1—Si	123.032 (5)
N2—Si—N1	110.096 (8)	Si—N1—Si	113.708 (10)
N1—Si—N1	108.026 (8)	Si—N2—Si	119.998 (5)
N1—Si—N1	108.026 (8)	Si—N2—Si	120.002 (4)
N1—Si—N1	113.708 (8)	Si—N2—Si	120.001 (4)

(200K-N) top

Crystal data top

N₄Si₃	D_x = 3.204 Mg m⁻³
M_r = 140.31	Syn x radiation, λ = 0.75037 Å
Hexagonal, P6₃	Cell parameters from 12 reflections
Hall symbol: p 6c	θ = 52.4–56.0°
a = 7.6015 (3) Å	µ = 1.54 mm⁻¹
c = 2.9061 (1) Å	T = 200 K
V = 145.43 (1) Å³	Irregular, colourless
Z = 1.5	0.04 × 0.03 × 0.02 mm
F(000) = 140

Data collection top

PF-BL14A Rigaku 4circle diffractometer	852 reflections with F > .00 sig(F )
Radiation source: Synchrotron	R_int = 0.028
Double Si monochromator	θ_max = 68.9°, θ_min = 3.3°
%w/2%q scans	h = −18→18
Absorption correction: analytical ?	k = −18→18
T_min = 0.932, T_max = 0.972	l = −7→7
12331 measured reflections	6 standard reflections every 200 reflections
866 independent reflections	intensity decay: none

Refinement top

Refinement on F	0 constraints
Least-squares matrix: full	Weighting scheme based on measured s.u.'s
R[F² > 2σ(F²)] = 0.013	(Δ/σ)_max = 0.004
wR(F²) = 0.011	Δρ_max = 0.38 e Å⁻³
S = 1.76	Δρ_min = −0.34 e Å⁻³
866 reflections	Extinction correction: Zachariasen, Eq22 p292 "Cryst. Comp." Munksgaard 1970
21 parameters	Extinction coefficient: 1600.000
0 restraints	Absolute structure: see text

Crystal data top

N₄Si₃	Z = 1.5
M_r = 140.31	Syn x radiation, λ = 0.75037 Å
Hexagonal, P6₃	µ = 1.54 mm⁻¹
a = 7.6015 (3) Å	T = 200 K
c = 2.9061 (1) Å	0.04 × 0.03 × 0.02 mm
V = 145.43 (1) Å³

Data collection top

PF-BL14A Rigaku 4circle diffractometer	852 reflections with F > .00 sig(F )
Absorption correction: analytical ?	R_int = 0.028
T_min = 0.932, T_max = 0.972	6 standard reflections every 200 reflections
12331 measured reflections	intensity decay: none
866 independent reflections

Refinement top

R[F² > 2σ(F²)] = 0.013	0 restraints
wR(F²) = 0.011	Δρ_max = 0.38 e Å⁻³
S = 1.76	Δρ_min = −0.34 e Å⁻³
866 reflections	Absolute structure: see text
21 parameters

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

	x	y	z	U_iso*/U_eq
Si	0.768482 (9)	0.174583 (9)	0.25000	0.00272 (2)
N1	0.03051 (2)	0.33030 (3)	0.2485 (4)	0.00380 (3)
N2	0.66666	0.33333	0.2469 (9)	0.00366 (6)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Si	0.00298 (2)	0.00279 (2)	0.00230 (2)	0.001377 (14)	0.00009 (11)	0.00006 (11)
N1	0.00307 (4)	0.00486 (4)	0.00277 (4)	0.00146 (3)	−0.0001 (2)	−0.0008 (2)
N2	0.00324 (4)	0.00324 (4)	0.00449 (9)	0.00162 (2)	0.00000	0.00000

Geometric parameters (Å, º) top

Si—N2	1.7290 (1)	Si—N1	1.7352 (2)
Si—N1	1.7319 (10)	Si—N1	1.7390 (10)

N2—Si—N1	110.40 (8)	Si—N1—Si	123.25 (6)
N2—Si—N1	106.599 (9)	Si—N1—Si	113.710 (9)
N2—Si—N1	109.78 (8)	Si—N1—Si	122.82 (6)
N1—Si—N1	108.19 (4)	Si—N2—Si	119.999 (5)
N1—Si—N1	113.71 (3)	Si—N2—Si	119.998 (4)
N1—Si—N1	107.87 (4)	Si—N2—Si	119.995 (5)

(150K-C) top

Crystal data top

N₄Si₃	D_x = 3.204 Mg m⁻³
M_r = 140.31	Syn x radiation, λ = 0.75037 Å
Hexagonal, P6₃/m	Cell parameters from 12 reflections
Hall symbol: -p 6c	θ = 52.3–56.0°
a = 7.6020 (2) Å	µ = 1.54 mm⁻¹
c = 2.9060 (1) Å	T = 150 K
V = 145.44 (1) Å³	Irregular, colourless
Z = 1.5	0.04 × 0.03 × 0.02 mm
F(000) = 140

Data collection top

PF-BL14A Rigaku 4circle diffractometer	786 reflections with F > .00 sig(F )
Radiation source: Synchrotron	R_int = 0.027
Double Si monochromator	θ_max = 65.1°, θ_min = 3.3°
%w/2%q scans	h = −18→18
Absorption correction: analytical ?	k = −18→18
T_min = 0.932, T_max = 0.972	l = −7→7
8549 measured reflections	6 standard reflections every 100 reflections
796 independent reflections	intensity decay: none

Refinement top

Refinement on F	0 constraints
Least-squares matrix: full	Weighting scheme based on measured s.u.'s
R[F² > 2σ(F²)] = 0.014	(Δ/σ)_max = 0.002
wR(F²) = 0.014	Δρ_max = 0.51 e Å⁻³
S = 1.84	Δρ_min = −0.40 e Å⁻³
796 reflections	Extinction correction: Zachariasen, Eq22 p292 "Cryst. Comp." Munksgaard 1970
16 parameters	Extinction coefficient: 2090 (375)
0 restraints	Absolute structure: see text

Crystal data top

N₄Si₃	Z = 1.5
M_r = 140.31	Syn x radiation, λ = 0.75037 Å
Hexagonal, P6₃/m	µ = 1.54 mm⁻¹
a = 7.6020 (2) Å	T = 150 K
c = 2.9060 (1) Å	0.04 × 0.03 × 0.02 mm
V = 145.44 (1) Å³

Data collection top

PF-BL14A Rigaku 4circle diffractometer	786 reflections with F > .00 sig(F )
Absorption correction: analytical ?	R_int = 0.027
T_min = 0.932, T_max = 0.972	6 standard reflections every 100 reflections
8549 measured reflections	intensity decay: none
796 independent reflections

Refinement top

R[F² > 2σ(F²)] = 0.014	0 restraints
wR(F²) = 0.014	Δρ_max = 0.51 e Å⁻³
S = 1.84	Δρ_min = −0.40 e Å⁻³
796 reflections	Absolute structure: see text
16 parameters

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

	x	y	z	U_iso*/U_eq
Si	0.768477 (12)	0.174561 (12)	0.25000	0.00248 (2)
N1	0.03050 (3)	0.33025 (3)	0.25000	0.00352 (5)
N2	0.66666	0.33333	0.25000	0.00343 (7)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Si	0.00272 (3)	0.00255 (3)	0.00211 (3)	0.00127 (2)	0.00000	0.00000
N1	0.00293 (5)	0.00444 (5)	0.00259 (5)	0.00139 (4)	0.00000	0.00000
N2	0.00306 (5)	0.00306 (5)	0.00415 (9)	0.00153 (3)	0.00000	0.00000

Geometric parameters (Å, º) top

Si—N2	1.7292 (1)	Si—N1	1.7354 (1)
Si—N1	1.7352 (2)	Si—N1	1.7354 (1)

N2—Si—N1	106.601 (11)	Si—N1—Si	123.033 (7)
N2—Si—N1	110.098 (10)	Si—N1—Si	123.033 (7)
N2—Si—N1	110.098 (10)	Si—N1—Si	113.708 (12)
N1—Si—N1	108.023 (9)	Si—N2—Si	119.998 (4)
N1—Si—N1	108.023 (9)	Si—N2—Si	120.002 (5)
N1—Si—N1	113.708 (10)	Si—N2—Si	120.001 (4)

(150K-N) top

Crystal data top

N₄Si₃	D_x = 3.204 Mg m⁻³
M_r = 140.31	Syn x radiation, λ = 0.75037 Å
Hexagonal, P6₃	Cell parameters from 12 reflections
Hall symbol: p 6c	θ = 52.3–56.0°
a = 7.6020 (2) Å	µ = 1.54 mm⁻¹
c = 2.9060 (1) Å	T = 150 K
V = 145.44 (1) Å³	Irregular, colourless
Z = 1.5	0.04 × 0.03 × 0.02 mm
F(000) = 140

Data collection top

PF-BL14A Rigaku 4circle diffractometer	787 reflections with F > .00 sig(F )
Radiation source: Synchrotron	R_int = 0.027
Double Si monochromator	θ_max = 65.1°, θ_min = 3.3°
%w/2%q scans	h = −18→18
Absorption correction: analytical ?	k = −18→18
T_min = 0.932, T_max = 0.972	l = −7→7
8549 measured reflections	6 standard reflections every 100 reflections
800 independent reflections	intensity decay: none

Refinement top

Refinement on F	0 constraints
Least-squares matrix: full	Weighting scheme based on measured s.u.'s
R[F² > 2σ(F²)] = 0.015	(Δ/σ)_max = 0.001
wR(F²) = 0.014	Δρ_max = 0.44 e Å⁻³
S = 1.84	Δρ_min = −0.44 e Å⁻³
265 reflections	Extinction correction: Zachariasen, Eq22 p292 "Cryst. Comp." Munksgaard 1970
22 parameters	Extinction coefficient: 384 (489)
0 restraints	Absolute structure: see text

Crystal data top

N₄Si₃	Z = 1.5
M_r = 140.31	Syn x radiation, λ = 0.75037 Å
Hexagonal, P6₃	µ = 1.54 mm⁻¹
a = 7.6020 (2) Å	T = 150 K
c = 2.9060 (1) Å	0.04 × 0.03 × 0.02 mm
V = 145.44 (1) Å³

Data collection top

PF-BL14A Rigaku 4circle diffractometer	787 reflections with F > .00 sig(F )
Absorption correction: analytical ?	R_int = 0.027
T_min = 0.932, T_max = 0.972	6 standard reflections every 100 reflections
8549 measured reflections	intensity decay: none
800 independent reflections

Refinement top

R[F² > 2σ(F²)] = 0.015	0 restraints
wR(F²) = 0.014	Δρ_max = 0.44 e Å⁻³
S = 1.84	Δρ_min = −0.44 e Å⁻³
265 reflections	Absolute structure: see text
22 parameters

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

	x	y	z	U_iso*/U_eq
Si	0.76847 (2)	0.17453 (2)	0.25000	0.00246 (4)
N1	0.03054 (5)	0.33023 (6)	0.2459 (6)	0.00343 (7)
N2	0.66666	0.33333	0.2502 (17)	0.00338 (10)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Si	0.00268 (4)	0.00254 (4)	0.00209 (4)	0.00126 (3)	0.0001 (2)	−0.0002 (2)
N1	0.00287 (8)	0.00428 (9)	0.00252 (9)	0.00133 (7)	0.0000 (4)	0.0009 (4)
N2	0.00304 (8)	0.00304 (8)	0.00406 (14)	0.00152 (4)	0.00000	0.00000

Geometric parameters (Å, º) top

Si—N2	1.7294 (1)	Si—N1	1.7451 (15)
Si—N1	1.7355 (4)	Si—N1	1.7252 (15)

N2—Si—N1	106.602 (18)	Si—N1—Si	123.63 (9)
N2—Si—N1	110.00 (15)	Si—N1—Si	122.42 (9)
N2—Si—N1	110.20 (15)	Si—N1—Si	113.73 (2)
N1—Si—N1	107.56 (6)	Si—N2—Si	119.997 (7)
N1—Si—N1	108.46 (6)	Si—N2—Si	120.002 (6)
N1—Si—N1	113.73 (5)	Si—N2—Si	120.001 (8)

Experimental details

	(295K-C)	(295K-N)	(200K-C)	(200K-N)
Crystal data
Chemical formula	N₄Si₃	N₄Si₃	N₄Si₃	N₄Si₃
M_r	140.31	140.31	140.31	140.31
Crystal system, space group	Hexagonal, P6₃/m	Hexagonal, P6₃	Hexagonal, P6₃/m	Hexagonal, P6₃
Temperature (K)	295	295	200	200
a, c (Å)	7.6044 (1), 2.9063 (1)	7.6044 (1), 2.9063 (1)	7.6015 (3), 2.9061 (1)	7.6015 (3), 2.9061 (1)
V (Å³)	145.55 (1)	145.55 (1)	145.43 (1)	145.43 (1)
Z	1.5	1.5	1.5	1.5
Radiation type	Syn x, λ = 0.75022 Å	Syn x, λ = 0.75022 Å	Syn x, λ = 0.75037 Å	Syn x, λ = 0.75037 Å
µ (mm⁻¹)	1.53	1.53	1.54	1.54
Crystal size (mm)	0.08 × 0.08 × 0.08 × 0.04 (radius)	0.08 × 0.08 × 0.08 × 0.04 (radius)	0.04 × 0.03 × 0.02	0.04 × 0.03 × 0.02

Data collection
Diffractometer	PF-BL14A Rigaku 4circle diffractometer	PF-BL14A Rigaku 4circle diffractometer	PF-BL14A Rigaku 4circle diffractometer	PF-BL14A Rigaku 4circle diffractometer
Absorption correction	For a sphere	For a sphere	Analytical	Analytical
T_min, T_max	0.939, 0.940	0.939, 0.940	0.932, 0.972	0.932, 0.972
No. of measured, independent and observed [F > .00 sig(F )] reflections	8577, 800, 792	8577, 800, 792	12331, 866, 852	12331, 866, 852
R_int	0.025	0.025	0.028	0.028
(sin θ/λ)_max (Å⁻¹)	1.208	1.208	1.243	1.243

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.020, 0.015, 2.01	0.018, 0.014, 1.88	0.014, 0.011, 1.89	0.013, 0.011, 1.76
No. of reflections	796	796	866	866
No. of parameters	16	22	16	21
Δρ_max, Δρ_min (e Å⁻³)	0.61, −0.53	0.53, −0.48	0.45, −0.37	0.38, −0.34
Absolute structure	See text	See text	See text	See text

	(150K-C)	(150K-N)
Crystal data
Chemical formula	N₄Si₃	N₄Si₃
M_r	140.31	140.31
Crystal system, space group	Hexagonal, P6₃/m	Hexagonal, P6₃
Temperature (K)	150	150
a, c (Å)	7.6020 (2), 2.9060 (1)	7.6020 (2), 2.9060 (1)
V (Å³)	145.44 (1)	145.44 (1)
Z	1.5	1.5
Radiation type	Syn x, λ = 0.75037 Å	Syn x, λ = 0.75037 Å
µ (mm⁻¹)	1.54	1.54
Crystal size (mm)	0.04 × 0.03 × 0.02	0.04 × 0.03 × 0.02

Data collection
Diffractometer	PF-BL14A Rigaku 4circle diffractometer	PF-BL14A Rigaku 4circle diffractometer
Absorption correction	Analytical	Analytical
T_min, T_max	0.932, 0.972	0.932, 0.972
No. of measured, independent and observed [F > .00 sig(F )] reflections	8549, 796, 786	8549, 800, 787
R_int	0.027	0.027
(sin θ/λ)_max (Å⁻¹)	1.208	1.208

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.014, 0.014, 1.84	0.015, 0.014, 1.84
No. of reflections	796	265
No. of parameters	16	22
Δρ_max, Δρ_min (e Å⁻³)	0.51, −0.40	0.44, −0.44
Absolute structure	See text	See text

Computer programs: Diff14A, Vaalsta & Hester 1997, Xtal3.7 LATCON, Xtal DIFDAT SORTRF ABSORB ADDREF, already known structure, Xtal CRYLSQ, Xtal BONDLA CIFIO.

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Format		BIBTeX
		EndNote
		RefMan
		Refer
		Medline
		CIF
		SGML
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Format		BIBTeX
		EndNote
		RefMan
		Refer
		Medline
		CIF
		SGML
		Text
		Plain Text