中文摘要：

采用第一原理框架下的平面波＋赝势方法,对Ge_3N_4的三种新结构进行了计算.计算结果表明四方、单斜和正交结构的氮化锗满足力学和热力学稳定条件,都可以稳定存在.o-Ge_3N_4的抗剪切能力和硬度都是三者之中最高的.本文得到了三种相的声子谱,即介电函数、能量损失谱和光吸收谱;研究发现在可见光区域三相的吸收都很弱,主要呈现出紫外吸收特征.介电函数虚部的峰值是由N-2p轨道的电子向Ge-4s和4p轨道跃迁形成的.声子谱表现出N原子和Ge原子杂化的特征.此外,也成功地得到了静态介电常数和离子体频率.

英文摘要：

The first-principles calculation was carried out for the novel Ge_3N_4 compounds through the planewave pseudo-potential method.The results showed that the tetragonal,monoclinic and orthorhombic structures can retain their stabilities at 0GPa.o-Ge_3N_4 has the highest tensile resistance and hardness among the three phases.The phonon dispersion,dielectric function,energy loss function and optical absorption are successfully obtained.Ge_3N_4 have weak absorptions in the visible light region,and the UV absorption characters are strong.The peak of the imaginary dielectric function is mainly contributed by the electron transitions from the N-2p band to the Ge-4sand 4p bands.The phonon dispersion curves reflect the characters between hybridization of N and Ge.Besides,the static dielectric constant and plasma frequency of t-Ge_3N_4,m-Ge_3N_4 and o-Ge_3N_4 are also obtained.