| 摘 要： | The structural, mechanical, electronic, mechanical anisotropy, and thermal properties of boron nitride(BN) polymorphs, such as B_4 N-4-Ⅰ and B4 N4-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 B_4 N_4-Ⅰ is dynamically and mechanically stable at the pressure of 0 GPa and temperature of 0 K. Anisotropic calculations indicate that both B_4 N_4-Ⅰ and B4 N4-Ⅱ exhibit higher anisotropy of Young's modulus than cubic BN(c-BN). B_4 N_4-Ⅱ and B_4 N_4-Ⅰ present indirect and wide band gaps of 5.32 eV and 4.86 eV, respectively. In addition, B_4 N_4-Ⅰ is more brittle than B_4 N_4-Ⅱ. Moreover, the minimum thermal conductivity,κmin, of B4 N4-Ⅱ at 300 K is 1.92 W/(cm·K), which is slightly higher than those of B_4 N_4-Ⅰ and c-BN(1.84 W/(cm-K) and 1.83 W/(cm-K), respectively. However, κ_(min) of B_4 N_4-Ⅰ is slightly higher than that of c-BN.
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