新型超硬材料R3m-BC2N的弹性及其各向异性的研究

本文运用基于密度泛函理论框架下的第一性原理平面波超软赝势方法首先计算了R3m-BC2N的弹性普适各向异性指数A^U及各向异性分数比AB，AG，表明R3m-BC2N是弹性各向异性材料．然后研究了不同晶向上的拉伸与剪切的应力应变曲线．由于其各向异性，在1000]和0001]晶向上R3m-BC2N显脆性，而在（O001）0010]晶向上材料具有较强的韧性．接着利用声学波速计算得到传播方向为0001]，（0001）上的热导率，显示了此材料的热导率各向异性．最后计算其电子结构，得到其禁带宽度为3．756eV．综上，所有研究都为实验合成R3m—BC2N提供了一定的理论基础．

Investigations of elastic and anisotropic of new superhard material R3m-BCeN

Firstly, based on the first-principles density functional theory with plane wave psuedopotential methods, the elastic universal anisotropic index A^U, percent anisotropy AB and AG of R3m-BC2N are calculated. It is found that R3m-BC2N is elastic anisotropic materials. Secondly, due to its anisotropic, R3m-BC2N is brittle in the 1000] and 0001] direction, whereas it has strong toughness in the （0001）0001] direction. Next, we obtain the thermal conductivity in the 0001] and （0001） direction by using the acoustic velocities, it shows that R3m-BC2N appear the thermal conductivity anisotropic. In the last, we calculate electronic structure of R3m-BC2N, and band gap is 3.756 eV. In summary, the studies of R3m-BC2N provide a theoretical basis for experimental synthesis R3m-BC2N.