A first-principles study of uniaxial compression of boron carbide doped by aluminum in intercosahedral chain

DOI: 10.62564/M4-VB1846

Vladyslav Bilyi, Oleksandr Vasiliev

Frantsevich Institute for Problems of Materials Science National Academy of Science of Ukraine


Boron carbide is a widely used impact-resistant ceramic due to its hardness, low density, and high Hugonio elastic limit, but it is prone to amorphization under high non-hydrostatic loads. Fanchini [1] suggested that the cause of amorphization lies in the (B₁₂)C-C-C boron carbide polytype, namely in the intercosahedral C-C-C chain. Previously, we determined [2] that the substitution of aluminum in the center of the chain is possible, and the most likely configuration is (B₁₂)C^Al^C. In this work, we consider the simulation of uniaxial compression along the intercosahedral chain of (B₁₂)C^Al^C and (B₁₂)C-C-C. For both configurations, we calculate the dependence of uniaxial stress on uniaxial strain and determine the maximum uniaxial stress and elastic strain values. We used a slightly modified method of uniaxial compressing that was described in [3]. The simulation was performed using the Quantum Espresso software package. A 2x2x1 unit cells of (B₁₂)C-C-C hexagonal supercell was constructed along the intercosahedral chain. All central carbon atoms were changed to aluminum and shifted in the same direction. Compression simulations were performed with a step size of 0.01 of the uniaxial elastic strain. Parameters used in the calculation include: kinetic energy cutoff for wavefunctions of 100 Ry, convergence criteria of $10^{-6}$ Ry for the self-consistent field and $10^{-3}$ Ry/Bohr for forces on the atoms, gamma point only for Brillouin zone, and gaussian spreading of $10^{-4}$ Ry. Our results show that the introduction of aluminum into the chain of (B₁₂)C-C-C polytype leads to a decrease in the maximum elastic strain (from 0.24 to 0.17) and the maximum uniaxial stress (from 161 GPa to 94 GPa) that the system can withstand.  Consequently, the (B₁₂)C^Al^C configuration has lower mechanical properties compared to the (B₁₂)C-C-C polytype of boron carbide. No mechanism for improving the characteristics of boron carbide was identified.

Keywords
First-principles, Boron carbide, Amorphization, Boron carbide doping

Acknowledgments
Not provided

References
[1] G. Fanchini, J. W. McCauley, and M. Chhowalla, ‘Behavior of Disordered Boron Carbide under Stress’, Phys. Rev. Lett., 2006. V. 97, No. 3, P. 035502. [2] O. Vasiliev, V. Bilyi, Y. Zaulychnyy, and V. Kartuzov, ‘Ground states in B4C-Al system’, presented at the HighMatTech-2023, Kyiv, Ukraine, Oct. 2023. [3] S. Aryal, P. Rulis, and W. Y. Ching, ‘Mechanism for amorphization of boron carbide B₄C under uniaxial compression’, Phys. Rev. B 2011. V. 84, No. 18, P. 184112.