压力下CaN_2结构稳定性和电子结构的第一性原理研究  

A first-principles study on the structure stabilities and electronic structures of CaN_2 under pressure

作　　者：余飞[1] 徐明[1] 孙久勋[2,3] 

机构地区：[1]西南民族大学电气信息工程学院,成都610041 [2]电子科技大学应用物理系,成都610054 [3]中国工程物理研究院流体物理研究所冲击波物理与爆轰物理实验室,绵阳621900

出　　处：《原子与分子物理学报》2017年第1期161-168,共8页Journal of Atomic and Molecular Physics

基　　金：国家民委科研项目(14XNZ018)

摘　　要：通过运用基于密度泛函理论的第一性原理计算方法结合广义梯度近似对压力下CaN_2的结构稳定性和电子结构进行了理论研究.对结构稳定性的研究表明,ZnCl_2型结构是CaN_2在环境压力下最稳定的结构,而实验上观察到的CaC_2-I型结构是CaN_2高压下(>8.7 GPa)的稳定性结构.在50 GPa的压力范围内,CaN_2将发生从ZnCl_2型结构到ThC_2型结构再到CaC_2-I型结构的两次压致结构相变,其相变压力分别为0.81 GPa和8.77 GPa.而对电子结构的研究表明ZnCl_2型、ThC_2型和CaC_2-I型三种结构的CaN_2都表现出了金属特征,三种结构CaN_2当中Ca-N键的离子-共价性特征和N原子间的N=N双键特征得到了确认.The structural stabilities and electronic properties of CaN2 under pressure have been investigated by using first - principles plane - wave pseudopotential density functional theory within the generalized gradient approximation （GGA）. The obtained results show that the ZnCl2 - type structure is the ground - state of CaN2 at ambient pressure. The CaC2 -I -type structure observed in experiment, however, becomes the thermodynami- cally preferred phase at high pressures （ 〉 8.77 GPa）. Two pressure - induced phase transitions are found at 0. 81 and 8.77 GPa, from the initial ZnCl2 - type structure （ Space group Pna21 ） through a ThC2 - type structure （Space group C2/c） to a CaC2 -I- type structure （Space group I4/mmm）. Moreover, electronic structure calculations reveal that CaN2 in all three structures are metallic. The covalent - ionic nature of Ca - N bonding and the covalent N = N double bonding in all three CaN2 structures are confirmed.

关 键 词：二氮化钙 高压相变 电子结构 第一性原理 

分 类 号：O414.13[理学—理论物理] O521[理学—物理]