中文摘要：

采用基于密度泛函理论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系统研究了三方相和四方相PbZr_（0.5）Ti_（0.5）O_3的能量稳定性、原子结构以及电子结构.计算结果表明三方相的能量比四方相低,说明三方相结构更加稳定,并且发现利用广义梯度近似计算的结构参数与实验值符合得更好.电子结构表明,两种相的Ti/Zr的3d电子和O的2p电子间存在明显的轨道杂化,并且Ti-O之间的作用比Zr-O作用更强;Pb的6s和5d电子与O的2s和2p电子也分别存在轨道杂化.而三方相中Pb的5d电子与O的2s电子杂化比四方相更强,进一步说明三方相比四方相结构更加稳定.

英文摘要：

The energetic stability,the structural and the electronic properties of rhombohedral and tetragonal PbZr_（0.5）Ti_（0.5）O_2 are systematically investigated by the first-principles plane-wave pseudopotential and the virtual crystal approximation（VCA） based on the density functional theory,within the frameworks of local density approximation（LDA） and generalized gradient approximation（GGA）.Our calculation results show that the total energy of the rhombohedral phase is lower than that of the tetragonal phase,which suggests that the rhombohedral structure is more energetically stable than the tetragonal one.Furthermore,the structural parameters calculated in the GGA are well consistent with experimental values.From the analysis of electronic structure,we can find the strong hybridization between Ti/Zr d and O 2p both in two phases.Furthermore the hybridization between Ti-0 is stronger than that between Zr-O;there also exists the hybridization between Pb s,d and O 2s,2p.Moreover,the hybridization between Pb 5d and O 2s in the rhombohedral phase is stronger than that in the tetragonal phase,which indicates that the rhombohedral phase is more stable than the tetragonal phase.