Study of LiBC [Top][Japanese]
(Start 2/17, 2003)(Update 10/20, 2023)
[Outline]
We found the lattice anomaly of LiBC[1][2], HBC[4], C_{6}B_{2}[7] under a, baxis compression and HBC[6], hMgB(hBN type structure)[5][6] under caxis compression.
Lattice constants c for LiBC, HBC, C_{6}B_{2} contract under a, baxis compression.
Lattice constants a(b) for hMgB, HBC contract under caxis compression.
These anomalous behavior show a kind of negative Poisson ratios.
A crystal structure of LiBC is hexagonal (symmetry: P6_{3}/mmc) and BC and Li layered structure (AB stacking).
HBC, hMgB and C_{6}B_{2} are hypothetical compounds.
HBC is the same crystal structure of LiBC.
hMgB is the hexagonalBN crystal structure (P6_{3}/mmc).
LiBC (AB stacking) is semiconductor.
HBC and hMgB are metallic.
The lattice contraction of LiBC, HBC under Pxy = 50 GPa and hMgB under Pz = 50 GPa is about 0.01 A.
This is too small to observe experimentally.
Furthermore, the lattice contraction of aaxis for HBC under Pz = 20 GPa is quite small (0.001 A).
This anomaly of HBC disappears under Pz = 50 GPa.
The lattice contraction of C_{6}B_{2} under Pxy = 50 GPa is about 0.1 A, which is about 1 % of lattice constant c.
A interlayer interaction of C_{6}B_{2} is very weak (related with van der Waals force) and it may be problematic in the DFTLDA calculation.
Further, it is noted that C_{6}B_{2} has a possibility of superconductivity[7].
[Method]
Calculational methods are firstprinciples molecular dynamics (FPMD) using the pseudopotential (NCPS2K[go to other site]) + plane waves and Wien2K [package].
[Related Materials]
HBC[4][6], NaBC, MgBC, MgC_{2}, hMgB[5][6], C_{6}B_{2}[7] etc.
In detail, Please see "references" below.
[Band] structure of LiBC (AB stacking, P6_{3}/mmc symmetry, png [12 kb])
[Band] structure of LiBC (AA stacking, Semimetallic, P6m2 symmetry, png [27.5 kb])
[Band] structure of HBC (AB stacking, P6_{3}/mmc symmetry, png [9.3 kb])
[Band] structure of hMgB (HexagonalBN structure:P6_{3}/mmc symmetry, png [12.2 kb])
(References)
[1] K. Kobayashi and M. Arai, "LiBC and related compounds under high pressure", Physica C 388  389 (2003) 201  202 (LT23).
[2] K. Kobayashi and M. Arai, "Lattice Anomaly of LiBC and Related Compounds under Anisotropic Compression", Journal of the Physical Society of Japan, Vol. 72, No. 2 (2003) 217.
[3] K. Kobayashi, M. Arai and K. Yamamoto, "Electronic and lattice properties of MgB_{2} and related phases under various compression conditions", Journal of the Physical Society of Japan, Vol. 72, No. 11 (2003) 2886:(Related paper).
[4] K. Kobayashi, M. Arai and T. Sasaki, "Lattice Anomalies of MBC (M = H, Li, Na) Under Anisotropic Compression", Trans. MRSJ, Vol. 29, No. 8, 37993802 (2004)[IUMRSICAM2003]:(Related paper).
[5] K. Kobayashi and M. Arai, "Lattice anomaly of MgB(hBN) under anisotropic compression", Mater. Trans., Vol. 45, No. 5, (2004) 1465  1468.
[6] K. Kobayashi and M. Arai, "Lattice anomaly of MgB(hBN) and related compounds under various compression conditions", Molecular Simulation, Vol. 30, No. 13  15 (2004) 981  986 (in Proceedings ICMSCSW2004).
[C_{6}B_{2}](ISS2004)
[7] K. Kobayashi, Y. Zenitani and J. Akimitsu, "FirstPrinciples Study of C_{6}B_{2}", Physica C, Vol. 426431, Part 1. (2005) 374  380 [ISS2004]. < As a result of more accurate calculations, we find that anharmonicity of C_{6}B_{2} is weak (b_{4}/(a_{2})^{2} is about 1).
[8] K. Kobayashi, M. Arai and K. Yamamoto, "FirstPrinciples Study of C_{6}M_{2} (M = B, Al, Mg, Li), C_{7}B and Related Compounds", Mater. Trans., Vol. 47, No. 11 (2006) 2629  2637[AlC_{2}, MgC_{2}, LiC_{2}, LiB_{2}].
[9] K. Kobayashi, M. Arai and K. Yamamoto, "Firstprinciples study of C_{6}B_{2} and related compounds", in proceedings of IWSDRM2005 (STAM, Vol. 7, Supplement 1 (2006) 71  77).
Related [papers] of LiBC (go to other site), of [MgB_{2}]
(Future schedule)
(Previous works)
 JPS meeting (Autumn, 2004, Aomori)
 ICMSCSW2004 (13  15 January, 2004, Tsukuba, Related)
 6th Asian Workshop on FirstPrinciples Electronic Structure Calculations (10 12 November, 2003, Tsukuba)
 IUMRSICAM2003 (8  13 October, 2003, Yokohama)
 JPS meeting (Autumn, 2003, Okayama)
(Related references)
 W. Yang, Z. Li, W. Shi, B. Xie and M. Yang, "On auxetic materials", Journal of Materials Science 39, 2369(2004)[Review](Very useful)
 T. G. J. Chandler, D. Vella, "Validity of Winkler's mattress model for thin elastomeric layers: Beyond Poisson's ratio", arXiv:2010.11133.

 (Related page)
 Information of B, C and [BCcompounds](+ C_{6}B_{2})

 (Useful link)
 Negative Poisson's ratio [materials](Prof. R. Lakes, University of Wisconsin)

 2nd [Workshop] on "Auxetics and Related Systems", Bedlewo (near Poznan), August 1923, 2005
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