四方和正交以及单斜相K_(0.5)Na_(0.5)NbO_3的结构稳定性和电子结构的第一性原理研究  

First-principles study of structural stability and electronic properties of tetragonal and orthorhombic as well as monoclinic K_(0.5)Na_(0.5)NbO_3

作　　者：刘士余[1] 余大书[1] 吕跃凯[1] 李德军[1] 曹茂盛[2] 

机构地区：[1]天津师范大学物理与电子信息学院,天津300387 [2]北京理工大学材料科学与工程学院,北京100081

出　　处：《物理学报》2013年第17期425-431,共7页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:11104203;11075116;51272176;51072024;51132002);天津师范大学引进人才基金(批准号:5RL100)资助的课题~~

摘　　要：采用基于密度泛函理论框架下的第一性原理超原胞方法和虚晶近似方法,在局域密度近似和广义梯度近似下,对四方和正交以及单斜相K0.5Na0.5NbO3的能量和原子结构以及电子结构进行了系统的研究.计算结果表明三种K0.5Na0.5NbO3相的能量差别较小,这与实验上它们之间容易发生相转化是一致的.进一步发现单斜相的能量比四方相和正交相低,说明单斜相结构更加稳定,并且理论计算的结构参数与实验值符合得很好.电子结构结果也表明单斜相的键合作用比四方相和正交相键合作用更强,进一步说明单斜相结构更加稳定.The energetic stability, structural and electronic properties of tetragonal, orthorhombic, as well as monoclinic Ko.sNao.sNbO3 are systematically studied using first-principles supercell model and virtual crystal approximation based on density functional theory with local density approximation and generalized gradient approximation. Our calculated results show that the total energy differences among the three Ko.5Nao.5YbO3 phases are small, which are well consistent with the easy phase equilibrium at the phase boundary in the experiments. Furthermore, we also find that the total energy of the monoclinic phase is lower than that of the other two phases, which suggests that the monoclinic structure is energetically more stable than the others. Moreover, the calculated structural parameters are in good agreement with experimental values. In addition, the electronic structure results show that the bonding interaction in the monoclinic structure is stronger than that in the other structures, also indicating that the monoclinic structure is the most stable one.

关 键 词：铌酸钾钠 四方相 单斜相 密度泛函理论 

分 类 号：O469[理学—凝聚态物理]