LiNH_2的晶格动力学、介电性质和热力学性质第一性原理研究

Lattice dynamical,dielectric and thermodynamic properties of LiNH_2 from first principles

采用基于密度泛函理论的平面波赝势方法,在局域密度近似下采用线性响应的密度泛函微扰理论计算了LiNH2的晶格动力学、介电性质和热力学性质,得到了布里渊区高对称方向上的声子色散曲线和相应的声子态密度,分析了LiNH2的红外和拉曼活性声子频率,同时给出它的介电张量和玻恩有效电荷张量.研究表明,LiNH2存在小的各向异性,计算所得结果与实验值和其他理论值符合较好.最后,利用得到的声子态密度进一步预测了LiNH2的热力学性质.

The lattice dynamical,dielectric properties and thermodynamic properties of LiNH2 are investigated by first principles calculations.Based on the density functional perturbation theory within the framework of linear response theory,the phonon dispersion curves and the phonon density of phonon states throughout the Brillouin zone are obtained.The calculated frequencies of the Raman active and infrared active modes are compared with previous experimental and theoretical results,and Born effective charge tensor as well as electronic dielectric permittivity tensor is presented.We find that the Born effective charge tensor of LiNH2 has quite small anisotropy.These calculated results are in good agreement with available experimental and theoretical values.Furthermore,the thermodynamic functions are predicted using the phonon density of states.