Theoretical Insight into the Structural Stability of KZnB3O6 Polymorphs with Different BOx Polyhedral Networks

详细信息    查看全文

• 作者：Lei Yang ; Weiliu Fan ; Yanlu Li ; Honggang Sun ; Lei Wei ; Xiufeng Cheng ; Xian Zhao
• 刊名：Inorganic Chemistry
• 出版年：2012
• 出版时间：June 18, 2012
• 年：2012
• 卷：51
• 期：12
• 页码：6762-6770
• 全文大小：535K
• 年卷期：v.51,no.12(June 18, 2012)
• ISSN：1520-510X

文摘

In general, the presence of shared edges of polyhedra for high-valence low-coordinated small cations is rarely seen except under extreme conditions such as high pressure. However, the ambient-pressure synthesis of KZnB₃O₆ built of edge-sharing BO₄ tetrahedra is contrary to this. By investigating the molecular dynamics, lattice dynamics, and electronic properties via density functional theory, we studied the origin of the phase stability of the edge-sharing (es) and 鈥渃orner-sharing (cs)鈥?KZnB₃O₆. Lattice dynamics results show that there are no phonon anomalies that could lead to the instability of es-KZnB₃O₆, which is consistent with molecular dynamics analysis. For 鈥渃s-KZnB₃O₆鈥? a soft mode at the G point in the phonon dispersion is identified that reflects the dynamic instability with respect to small distortions. Eigenvector analysis of the soft mode of 鈥渃s-KZnB₃O₆鈥?indicates that the instability comes from the linkage of ZnO₅ polyhedra rather than BO_x polyhedra. Electronic property calculation indicates that the edge-sharing BO₄ polyhedra connected by the longest B鈥揙 蟽 bonds provide a solid framework for es-KZnB₃O₆. In the case of 鈥渃s-KZnB₃O₆鈥? the overlong Zn鈥揙 bond possesses the smallest covalent nature and the least orbital overlap among the bonds in a ZnO₅ polyhedron, and these two features of the electronic structure reduce the stability of 鈥渃s-KZnB₃O₆鈥?compared to es-KZnB₃O₆. The electronic property calculation further confirms the results obtained from lattice dynamics analysis.