Literature DB >> 22904703

Boron carbide, B(13-x)C(2-y) (x = 0.12, y = 0.01).

Oksana Sologub1, Yuichi Michiue, Takao Mori.   

Abstract

Boron carbide phases exist over a widely varying compos-itional range B(12+x)C(3-x) (0.06 < x < 1.7). One idealized structure corresponds to the B(13)C(2) composition (space group R-3m) and contains one icosa-hedral B(12) unit and one linear C-B-C chain. The B(12) units are composed of crystallographically distinct B atoms B(P) (polar, B1) and B(Eq) (equatorial, B2). Boron icosa-hedra are inter-connected by C atoms via their B(Eq) atoms, forming layers parallel to (001), while the B(12) units of the adjacent layers are linked through inter-icosa-hedral B(P)-B(P) bonds. The unique B atom (B(C)) connects the two C atoms of adjacent layers, forming a C-B-C chain along [001]. Depending on the carbon concentration, the carbon and B(P) sites exhibit mixed B/C occupancies to varying degrees; besides, the B(C) site shows partial occupancy. The decrease in carbon content was reported to be realized via an increasing number of chainless unit cells. On the basis of X-ray single-crystal refinement, we have concluded that the unit cell of the given boron-rich crystal contains following structural units: [B(12)] and [B(11)C] icosa-hedra (about 96 and 4%, respectively) and C-B-C chains (87%). Besides, there is a fraction of unit cells (13%) with the B atom located against the triangular face of a neighboring icosa-hedron formed by B(Eq) (B2) thus rendering the formula B(0.87)(B(0.98)C(0.02))(12)(B(0.13)C(0.87))(2) for the current boron carbide crystal.

Entities:  

Year:  2012        PMID： 22904703      PMCID： PMC3414096          DOI： 10.1107/S1600536812033132

Source DB:  PubMed          Journal:  Acta Crystallogr Sect E Struct Rep Online        ISSN： 1600-5368


Related literature

For X-ray/neutron diffraction studies on boron carbide, see: Yakel (1975 ▶); Will et al. (1979 ▶); Larson (1986 ▶); Kwei & Morosin (1996 ▶). For the boron carbide homogeneity field, see: Bouchacourt & Thevenot (1985 ▶); Gosset & Colin (1991 ▶). For electronic structure and bonding properties, see: Domnich et al. (2011 ▶); Balakrishnarajan et al. (2007 ▶). For electronic properties and charge transport, see: Werheit (2009 ▶).

Experimental

Crystal data

C1.99B12.88 M = 163.14 Trigonal, a = 5.6530 (8) Å c = 12.156 (4) Å V = 336.42 (17) Å3 Z = 3 Mo Kα radiation μ = 0.10 mm−1 T = 293 K 0.45 × 0.30 × 0.21 mm

Data collection

Rigaku AFC 7R diffractometer 1489 measured reflections 284 independent reflections 184 reflections with I > 2σ(I) R int = 0.151 3 standard reflections every 150 reflections intensity decay: none

Refinement

R[F 2 > 2σ(F 2)] = 0.046 wR(F 2) = 0.109 S = 1.03 284 reflections 22 parameters 1 restraint Δρmax = 0.55 e Å−3 Δρmin = −0.37 e Å−3 Data collection: Rigaku/AFC Diffractometer Control Software (Rigaku, 1998 ▶); cell refinement: Rigaku/AFC Diffractometer Control Software; data reduction: TEXSAN (Molecular Structure Corporation, 1998 ▶); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: ATOMS (Dowty, 1999 ▶); software used to prepare material for publication: SHELXL97 and WinGX (Farrugia, 1999 ▶). Crystal structure: contains datablock(s) global, I. DOI: 10.1107/S1600536812033132/ru2039sup1.cif Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536812033132/ru2039Isup2.hkl Additional supplementary materials: crystallographic information; 3D view; checkCIF report
C1.99B12.88Dx = 2.416 Mg m−3
Mr = 163.14Mo Kα radiation, λ = 0.71073 Å
Trigonal, R3mCell parameters from 20 reflections
Hall symbol: -R 3 2"θ = 8–50°
a = 5.6530 (8) ŵ = 0.10 mm−1
c = 12.156 (4) ÅT = 293 K
V = 336.42 (17) Å3Prism, black
Z = 30.45 × 0.3 × 0.21 mm
F(000) = 229
Rigaku AFC 7R diffractometerθmax = 39.8°, θmin = 4.5°
ω–2θ scansh = −10→8
1489 measured reflectionsk = 0→10
284 independent reflectionsl = −21→21
184 reflections with I > 2σ(I)3 standard reflections every 150 reflections
Rint = 0.151 intensity decay: none
Refinement on F222 parameters
Least-squares matrix: full1 restraint
R[F2 > 2σ(F2)] = 0.046w = 1/[σ2(Fo2) + (0.0481P)2 + 0.3407P] where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.109(Δ/σ)max = 0.002
S = 1.03Δρmax = 0.55 e Å−3
284 reflectionsΔρmin = −0.37 e Å−3
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.
xyzUiso*/UeqOcc. (<1)
B10.44092 (16)0.55908 (16)0.05298 (12)0.0053 (3)0.958 (4)
C110.44092 (16)0.55908 (16)0.05298 (12)0.0053 (3)0.042 (4)
B20.50336 (16)0.49664 (16)0.19232 (11)0.0054 (3)
B30000.0118 (8)0.87
C1000.1177 (5)0.0071 (8)0.87 (2)
B11000.079 (4)0.0071 (8)0.13 (2)
U11U22U33U12U13U23
B10.0056 (4)0.0056 (4)0.0047 (5)0.0028 (5)−0.0001 (2)0.0001 (2)
C110.0056 (4)0.0056 (4)0.0047 (5)0.0028 (5)−0.0001 (2)0.0001 (2)
B20.0046 (4)0.0046 (4)0.0059 (5)0.0015 (4)−0.0003 (2)0.0003 (2)
B30.0099 (11)0.0099 (11)0.016 (2)0.0049 (6)00
C10.0041 (6)0.0041 (6)0.013 (2)0.0021 (3)00
B110.0041 (6)0.0041 (6)0.013 (2)0.0021 (3)00
B1—C11i1.731 (3)B2—B1ii1.8091 (15)
B1—B1i1.731 (3)B2—C11iii1.8091 (15)
B1—B21.801 (2)B2—B1iii1.8091 (15)
B1—B2ii1.8091 (15)B3—B110.96 (5)
B1—B2iii1.8091 (15)B3—B11vii0.96 (5)
B1—B1iv1.825 (3)B3—C1vii1.430 (6)
B1—C11iv1.825 (3)B3—C11.430 (6)
B1—C11v1.825 (3)C1—B2vi1.6239 (19)
B1—B1v1.825 (3)C1—B2iii1.6239 (19)
B2—C1vi1.6239 (19)C1—B2viii1.6239 (19)
B2—B11vi1.77 (2)B11—B2vi1.77 (2)
B2—B2iii1.7778 (17)B11—B2iii1.77 (2)
B2—B2ii1.7778 (17)B11—B2viii1.77 (2)
B2—C11ii1.8091 (15)B11—B11vii1.92 (9)
C11i—B1—B1i0.00 (8)B11vi—B2—C11ii108.5 (11)
C11i—B1—B2118.22 (14)B2iii—B2—C11ii108.78 (7)
B1i—B1—B2118.22 (14)B2ii—B2—C11ii60.26 (7)
C11i—B1—B2ii121.45 (8)B1—B2—C11ii110.05 (9)
B1i—B1—B2ii121.45 (8)C1vi—B2—B1ii121.07 (19)
B2—B1—B2ii59.01 (5)B11vi—B2—B1ii108.5 (11)
C11i—B1—B2iii121.45 (8)B2iii—B2—B1ii108.78 (7)
B1i—B1—B2iii121.45 (8)B2ii—B2—B1ii60.26 (7)
B2—B1—B2iii59.01 (5)B1—B2—B1ii110.05 (9)
B2ii—B1—B2iii105.68 (11)C11ii—B2—B1ii0.00 (11)
C11i—B1—B1iv125.36 (8)C1vi—B2—C11iii121.07 (19)
B1i—B1—B1iv125.36 (8)B11vi—B2—C11iii108.5 (11)
B2—B1—B1iv107.10 (6)B2iii—B2—C11iii60.26 (7)
B2ii—B1—B1iv107.02 (6)B2ii—B2—C11iii108.78 (7)
B2iii—B1—B1iv59.72 (5)B1—B2—C11iii110.05 (9)
C11i—B1—C11iv125.36 (8)C11ii—B2—C11iii60.56 (11)
B1i—B1—C11iv125.36 (8)B1ii—B2—C11iii60.56 (11)
B2—B1—C11iv107.10 (6)C1vi—B2—B1iii121.07 (19)
B2ii—B1—C11iv107.02 (6)B11vi—B2—B1iii108.5 (11)
B2iii—B1—C11iv59.72 (5)B2iii—B2—B1iii60.26 (7)
B1iv—B1—C11iv0.00 (9)B2ii—B2—B1iii108.78 (7)
C11i—B1—C11v125.36 (8)B1—B2—B1iii110.05 (9)
B1i—B1—C11v125.36 (8)C11ii—B2—B1iii60.56 (11)
B2—B1—C11v107.10 (6)B1ii—B2—B1iii60.56 (11)
B2ii—B1—C11v59.72 (5)C11iii—B2—B1iii0.00 (4)
B2iii—B1—C11v107.02 (6)B11—B3—B11vii180.0000 (10)
B1iv—B1—C11v60B11—B3—C1vii180.0000 (10)
C11iv—B1—C11v60B11vii—B3—C1vii0.0000 (10)
C11i—B1—B1v125.36 (8)B11—B3—C10.0000 (10)
B1i—B1—B1v125.36 (8)B11vii—B3—C1180.0000 (10)
B2—B1—B1v107.10 (6)C1vii—B3—C1180
B2ii—B1—B1v59.72 (5)B3—C1—B2vi100.1 (2)
B2iii—B1—B1v107.02 (6)B3—C1—B2iii100.1 (2)
B1iv—B1—B1v60B2vi—C1—B2iii117.01 (13)
C11iv—B1—B1v60B3—C1—B2viii100.1 (2)
C11v—B1—B1v0.00 (10)B2vi—C1—B2viii117.01 (13)
C1vi—B2—B11vi15.1 (12)B2iii—C1—B2viii117.01 (13)
C1vi—B2—B2iii121.49 (7)B3—B11—B2vi115.2 (13)
B11vi—B2—B2iii125.0 (2)B3—B11—B2iii115.2 (13)
C1vi—B2—B2ii121.49 (7)B2vi—B11—B2iii103.2 (16)
B11vi—B2—B2ii125.0 (2)B3—B11—B2viii115.2 (13)
B2iii—B2—B2ii108.39 (8)B2vi—B11—B2viii103.2 (16)
C1vi—B2—B1119.9 (2)B2iii—B11—B2viii103.2 (16)
B11vi—B2—B1135.0 (14)B3—B11—B11vii0.0000 (10)
B2iii—B2—B160.73 (7)B2vi—B11—B11vii115.2 (13)
B2ii—B2—B160.73 (7)B2iii—B11—B11vii115.2 (13)
C1vi—B2—C11ii121.07 (19)B2viii—B11—B11vii115.2 (13)
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