压力下NaN_3结构稳定性、力学性质和电子结构的理论研究

采用基于密度泛函理论的从头算平面波超软贋势方法研究了压力对NaN_3结构稳定性、力学性能以及电子结构的影响.对能量和力学参量的计算结果表明,R-3m结构是NaN_3在零压下的稳定性结构.随着压力的增加,在5 GPa的压力范围内NaN_3会发生从R-3m结构到C2/m结构的结构相变,而C2/m结构的NaN_3在压力超过20 GPa以后也不能够保持稳定.该结果与实验研究结果间取得了很好的一致.此外,对电子结构的研究表明,常压下两种结构NaN_3都表现出了绝缘体的性质.随着压力的增加,C2/m结构NaN_3的价带和导带宽度都略有增加,而带隙宽度略有减小.

Theoretical research on structure stabilities, mechanical properties and electronic structures of NaN3 under pressure

The structural stabilities, mechanical properties and electronic structures of NaN3 under pressure were investigated using the first-principle plane-wave ultrasoft pseudopotential methods based on the density functional theory. The calculated results show that R-3m structure is the stable structure of NaN3 at atmospheric pressure. As the pressure increases, NaN3 undergoes a pressure-induced phase transition from R-3m structure to C2/m structure and the transition pressure is less than 5 GPa. Once the pressure exceeds 20 GPa, C2/m structure NaN3 could not keep stable. Our results agree well with previous experimental results. Moreover, electronic structure calculations reveal that R-3m and C2/m structure NaN3 are isolator. For C2/m structure NaN3, with the increase of pressure, the valence band and conduction band become broader and the band gap values tend to decrease.