高压对氮化硼纳米管的几何结构、电子结构和光学性质的影响

Effect of high pressures on structural,electronic and optical properties of BN nanotube

运用密度泛函理论平面波赝势方法(PWP)和广义梯度近似(GGA),计算研究了纳米管BN(5,5)在不同压力条件下的几何结构、电子结构和光学性质.在高压条件下管口形状发生了较大的变化.与闪锌矿结构BN比较分析发现两种结构间存在一些性质上的差异:首先,在外压力作用下,BN(5,5)纳米管的带隙随压力增大而减小,变化率为-0·01795eV/GPa,而闪锌矿结构BN随压力增大而增大;其次光吸收谱在压力条件下,没有和闪锌矿结构BN一样发生“蓝移”,相反在红外方向有所拓展;但纳米管BN(5,5)电子的转移方向和立方BN相同,与BP(5,5)相反.通过分析电子态密度图,纳米管BN(5,5)有较强的离子性,随着压力的增大离子性减弱.

The structural, electronic and optical properties of BN （5,5） nanotube under high pressures were studied by means of quantum-mechanical calculations based on the density functional theory and pseudopotential method. It was found that the geometric structure has large distortion under pressures. Differences exist between BN （5,5） nanotube and zinc blende structure BN： firstly, the band gap of BN （5,5） nanotube increases with pressure with a slope of -0.01795eV/GPa; secondly, the absorption spectrum does not ＂blue shift＂, but stretches in the direction of infrared ; yet these two structures have same electronic transfer direction. The electron density map indicated that BN （5,5） has stronger ionicity, which weakens with pressure increasing.