Abstract
The structural, mechanical, electronic, mechanical anisotropy, and thermal properties of boron nitride (BN) polymorphs, such as B4N4-I and B4N4-II, are investigated under ambient pressure utilizing first-principles generalized gradient approximation calculations using an ultrasoft pseudopotential scheme. The phonon spectra and elastic constants reveal that B4N4-I is dynamically and mechanically stable at the pressure of 0 GPa and temperature of 0 K. Anisotropic calculations indicate that both B4N4-I and B4N4-II exhibit higher anisotropy of Young’s modulus than cubic BN (c-BN). B4N4-II and B4N4-I present indirect and wide band gaps of 5.32 eV and 4.86 eV, respectively. In addition, B4N4-I is more brittle than B4N4-II. Moreover, the minimum thermal conductivity, κmin, of B4N4-II at 300 K is 1.92 W/(cm·K), which is slightly higher than those of B4N4-I and c-BN (1.84 W/(cm·K) and 1.83 W/(cm·K), respectively. However, κmin of B4N4-I is slightly higher than that of c-BN.
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