Crystal structure refinements of stoichiometric Ni₃Se₂ and NiSe

Single crystals of Ni₃Se₂ (trinickel diselenide) and NiSe (nickel selenide) with stoichiometric chemical com­positions were grown in evacuated silica-glass tubes. The chemical com­positions of the single crystals of Ni₃Se₂ and NiSe were determined by scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM/EDS). The crystal structures of Ni₃Se₂ [rhombohedral, space group R32, a = 6.02813 (13), c = 7.24883 (16) Å, Z = 3] and NiSe [hexa­gonal, space group P6₃/mmc, a = 3.66147 (10), c = 5.35766 (16) Å, Z = 2] were analyzed by single-crystal X-ray diffraction and refined to yield R values of 0.020 and 0.018 for 117 and 85 unique reflections, respectively, with F_o > 4σ(F_o). R32 is a Sohncke type of space group where enanti­omeric structures can exist; the single-domain structure obtained by the refinement was confirmed to be correct by a Flack parameter of −0.05 (2). The existence of Ni—Ni bonds was confirmed in both com­pounds, in addition to the Ni—Se bonds. The value of the atomic displacement parameter (mean-square displacement) of each atom in NiSe was larger than that in Ni₃Se₂. The larger amplitude of the atoms in NiSe corresponds to longer Ni—Se and Ni—Ni bond lengths in NiSe than in Ni₃Se₂. The Debye temperatures, θ_D, estimated from observed mean-square displacements for Ni and Se in Ni₃Se₂, were 322 and 298 K, respectively, while those for Ni and Se in NiSe were 246 and 241 K, respectively. The existence of large cavities in the structure and the weak bonding force are likely responsible for the brittle and soft nature of the NiSe crystal.

Computing details

For both structures, data collection: CrysAlis PRO (Rigaku OD, 2019); cell refinement: CrysAlis PRO (Rigaku OD, 2019); data reduction: CrysAlis PRO (Rigaku OD, 2019); program(s) used to solve structure: OLEX2 (Dolomanov et al., 2009) and SHELXT2018 (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2018 (Sheldrick, 2015b); molecular graphics: VESTA (Momma & Izumi, 2011); software used to prepare material for publication: SHELXL2018 (Sheldrick, 2015b).

Trinickel diselenide (I)

Crystal data

Ni3Se2	Dx = 7.295 Mg m^−3
Mr = 334.05	Mo Kα radiation, λ = 0.71073 Å
Hexagonal, R32:H	Cell parameters from 5172 reflections
Hall symbol: R 3 2"	θ = 4.8–27.1°
a = 6.02813 (13) Å	µ = 41.99 mm^−1
c = 7.24883 (16) Å	T = 293 K
V = 228.12 (1) Å^3	Block, silver
Z = 3	0.12 × 0.09 × 0.08 mm
F(000) = 456

Data collection

Rigaku SuperNova Single Source diffractometer with a HyPix3000 detector	117 independent reflections
Mirror monochromator	117 reflections with I > 2σ(I)
Detector resolution: 10.0000 pixels mm^-1	Rint = 0.047
ω scans	θmax = 27.0°, θmin = 4.8°
Absorption correction: gaussian (CrysAlis PRO; Rigaku OD, 2019)	h = −7→7
Tmin = 0.056, Tmax = 0.135	k = −7→7
5554 measured reflections	l = −9→9

Refinement

Refinement on F^2	0 restraints
Least-squares matrix: full	w = 1/[σ^2(Fo^2) + (0.0318P)^2 + 1.1728P] where P = (Fo^2 + 2Fc^2)/3
R[F^2 > 2σ(F^2)] = 0.020	(Δ/σ)max < 0.001
wR(F^2) = 0.052	Δρmax = 1.15 e Å^−3
S = 1.37	Δρmin = −1.59 e Å^−3
117 reflections	Absolute structure: Flack x determined using 42 quotients [(I+)-(I-)]/[(I+)+(I-)] (Parsons et al., 2013)
9 parameters	Absolute structure parameter: −0.049 (19)

Special details

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

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

	x	y	z	Uiso*/Ueq
Se1	0.000000	0.000000	−0.25999 (13)	0.0061 (4)
Ni1	−0.2469 (2)	0.000000	0.000000	0.0070 (4)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Se1	0.0057 (5)	0.0057 (5)	0.0069 (6)	0.0029 (2)	0.000	0.000
Ni1	0.0062 (5)	0.0076 (7)	0.0075 (6)	0.0038 (3)	−0.0007 (2)	−0.0015 (4)

Geometric parameters (Å, º)

Se1—Ni1^i	2.3748 (8)	Se1—Ni1	2.4013 (10)
Se1—Ni1^ii	2.3748 (8)	Ni1—Ni1^iv	2.577 (2)
Se1—Ni1^iii	2.3748 (8)	Ni1—Ni1^v	2.577 (2)
Se1—Ni1^iv	2.4012 (10)	Ni1—Ni1^i	2.5795 (8)
Se1—Ni1^v	2.4012 (10)	Ni1—Ni1^vi	2.5795 (8)
Ni1^i—Se1—Ni1^ii	115.139 (17)	Se1^viii—Ni1—Ni1^iv	100.96 (2)
Ni1^i—Se1—Ni1^iii	115.138 (17)	Se1^ix—Ni1—Ni1^iv	57.54 (2)
Ni1^ii—Se1—Ni1^iii	115.138 (16)	Se1—Ni1—Ni1^iv	57.54 (2)
Ni1^i—Se1—Ni1^iv	125.03 (2)	Se1^vii—Ni1—Ni1^v	100.96 (2)
Ni1^ii—Se1—Ni1^iv	65.38 (2)	Se1^viii—Ni1—Ni1^v	157.35 (3)
Ni1^iii—Se1—Ni1^iv	111.71 (3)	Se1^ix—Ni1—Ni1^v	57.54 (2)
Ni1^i—Se1—Ni1^v	111.71 (3)	Se1—Ni1—Ni1^v	57.54 (2)
Ni1^ii—Se1—Ni1^v	125.02 (2)	Ni1^iv—Ni1—Ni1^v	60.0
Ni1^iii—Se1—Ni1^v	65.38 (2)	Se1^vii—Ni1—Ni1^i	57.81 (5)
Ni1^iv—Se1—Ni1^v	64.92 (5)	Se1^viii—Ni1—Ni1^i	98.23 (3)
Ni1^i—Se1—Ni1	65.38 (2)	Se1^ix—Ni1—Ni1^i	157.37 (5)
Ni1^ii—Se1—Ni1	111.71 (3)	Se1—Ni1—Ni1^i	56.82 (2)
Ni1^iii—Se1—Ni1	125.03 (2)	Ni1^iv—Ni1—Ni1^i	110.49 (5)
Ni1^iv—Se1—Ni1	64.92 (5)	Ni1^v—Ni1—Ni1^i	100.08 (2)
Ni1^v—Se1—Ni1	64.92 (5)	Se1^vii—Ni1—Ni1^vi	98.23 (3)
Se1^vii—Ni1—Se1^viii	100.03 (5)	Se1^viii—Ni1—Ni1^vi	57.81 (5)
Se1^vii—Ni1—Se1^ix	125.03 (2)	Se1^ix—Ni1—Ni1^vi	56.82 (2)
Se1^viii—Ni1—Se1^ix	102.855 (10)	Se1—Ni1—Ni1^vi	157.38 (5)
Se1^vii—Ni1—Se1	102.855 (10)	Ni1^iv—Ni1—Ni1^vi	100.08 (2)
Se1^viii—Ni1—Se1	125.03 (2)	Ni1^v—Ni1—Ni1^vi	110.49 (5)
Se1^ix—Ni1—Se1	103.41 (6)	Ni1^i—Ni1—Ni1^vi	144.71 (8)
Se1^vii—Ni1—Ni1^iv	157.35 (3)

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

Nickel selenide (II)

Crystal data

NiSe	Dx = 7.350 Mg m^−3
Mr = 137.67	Mo Kα radiation, λ = 0.71073 Å
Hexagonal, P63/mmc	Cell parameters from 2443 reflections
Hall symbol: -P 6c 2c	θ = 3.8–39.7°
a = 3.66147 (10) Å	µ = 43.98 mm^−1
c = 5.35766 (16) Å	T = 293 K
V = 62.20 (1) Å^3	Plate, silver
Z = 2	0.13 × 0.11 × 0.03 mm
F(000) = 124

Data collection

Rigaku SuperNova Single Source diffractometer with a HyPix3000 detector	91 independent reflections
Mirror monochromator	85 reflections with I > 2σ(I)
Detector resolution: 10.0000 pixels mm^-1	Rint = 0.054
ω scans	θmax = 39.7°, θmin = 3.8°
Absorption correction: gaussian (CrysAlis PRO; Rigaku OD, 2019)	h = −6→6
Tmin = 0.040, Tmax = 0.349	k = −6→6
2898 measured reflections	l = −9→9

Refinement

Refinement on F^2	5 parameters
Least-squares matrix: full	0 restraints
R[F^2 > 2σ(F^2)] = 0.018	w = 1/[σ^2(Fo^2) + (0.0278P)^2] where P = (Fo^2 + 2Fc^2)/3
wR(F^2) = 0.043	(Δ/σ)max < 0.001
S = 1.24	Δρmax = 1.23 e Å^−3
91 reflections	Δρmin = −1.73 e Å^−3

Special details

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

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

	x	y	z	Uiso*/Ueq
Se1	0.333333	0.666667	0.250000	0.00930 (13)
Ni2	0.000000	0.000000	0.000000	0.01201 (15)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Se1	0.00730 (14)	0.00730 (14)	0.01331 (18)	0.00365 (7)	0.000	0.000
Ni2	0.01180 (17)	0.01180 (17)	0.0124 (2)	0.00590 (9)	0.000	0.000

Geometric parameters (Å, º)

Se1—Ni2^i	2.5026 (1)	Se1—Ni2^iv	2.5026 (1)
Se1—Ni2^ii	2.5026 (1)	Se1—Ni2^v	2.5026 (1)
Se1—Ni2^iii	2.5026 (1)	Ni2—Ni2^v	2.6788 (1)
Se1—Ni2	2.5026 (1)	Ni2—Ni2^vi	2.6788 (1)
Ni2^i—Se1—Ni2^ii	64.717 (2)	Se1^viii—Ni2—Se1^x	85.968 (1)
Ni2^i—Se1—Ni2^iii	94.032 (1)	Se1—Ni2—Se1^x	85.968 (1)
Ni2^ii—Se1—Ni2^iii	130.033 (1)	Se1^ix—Ni2—Se1^x	94.032 (1)
Ni2^i—Se1—Ni2	130.033 (1)	Se1^vii—Ni2—Se1^xi	85.968 (1)
Ni2^ii—Se1—Ni2	94.032 (1)	Se1^viii—Ni2—Se1^xi	94.032 (1)
Ni2^iii—Se1—Ni2	130.033 (1)	Se1—Ni2—Se1^xi	94.032 (1)
Ni2^i—Se1—Ni2^iv	130.033 (1)	Se1^ix—Ni2—Se1^xi	85.968 (1)
Ni2^ii—Se1—Ni2^iv	94.032 (1)	Se1^x—Ni2—Se1^xi	180.0
Ni2^iii—Se1—Ni2^iv	64.717 (2)	Se1^vii—Ni2—Ni2^v	122.359 (1)
Ni2—Se1—Ni2^iv	94.032 (1)	Se1^viii—Ni2—Ni2^v	57.641 (1)
Ni2^i—Se1—Ni2^v	94.032 (1)	Se1—Ni2—Ni2^v	57.641 (1)
Ni2^ii—Se1—Ni2^v	130.033 (1)	Se1^ix—Ni2—Ni2^v	122.359 (1)
Ni2^iii—Se1—Ni2^v	94.032 (1)	Se1^x—Ni2—Ni2^v	122.359 (1)
Ni2—Se1—Ni2^v	64.717 (2)	Se1^xi—Ni2—Ni2^v	57.641 (1)
Ni2^iv—Se1—Ni2^v	130.033 (1)	Se1^vii—Ni2—Ni2^vi	57.641 (1)
Se1^vii—Ni2—Se1^viii	180.0	Se1^viii—Ni2—Ni2^vi	122.359 (1)
Se1^vii—Ni2—Se1	85.968 (1)	Se1—Ni2—Ni2^vi	122.359 (1)
Se1^viii—Ni2—Se1	94.032 (1)	Se1^ix—Ni2—Ni2^vi	57.641 (1)
Se1^vii—Ni2—Se1^ix	94.032 (1)	Se1^x—Ni2—Ni2^vi	57.641 (1)
Se1^viii—Ni2—Se1^ix	85.968 (1)	Se1^xi—Ni2—Ni2^vi	122.359 (1)
Se1—Ni2—Se1^ix	180.0	Ni2^v—Ni2—Ni2^vi	180.0
Se1^vii—Ni2—Se1^x	94.032 (1)

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