Role of Acentric Displacements on the Crystal Structure and Second-Harmonic Generating Properties of RbPbCO3F and CsPbCO3F

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• 作者：T. Thao Tran ; P. Shiv Halasyamani ; James M. Rondinelli
• 刊名：Inorganic Chemistry
• 出版年：2014
• 出版时间：June 16, 2014
• 年：2014
• 卷：53
• 期：12
• 页码：6241-6251
• 全文大小：566K
• 年卷期：v.53,no.12(June 16, 2014)
• ISSN：1520-510X

文摘

Two lead fluorocarbonates, RbPbCO₃F and CsPbCO₃F, were synthesized and characterized. The materials were synthesized through solvothermal and conventional solid-state techniques. RbPbCO₃F and CsPbCO₃F were structurally characterized by single-crystal X-ray diffraction and exhibit three-dimensional (3D) crystal structures consisting of corner-shared PbO₆F₂ polyhedra. For RbPbCO₃F, infrared and ultraviolet鈥搗isible spectroscopy and thermogravimetric and differential thermal analysis measurements were performed. RbPbCO₃F is a new noncentrosymmetric material and crystallizes in the achiral and nonpolar space group P6̅m2 (crystal class 6虆m2). Powder second-harmonic generation (SHG) measurements on RbPbCO₃F and CsPbCO₃F using 1064 nm radiation revealed an SHG efficiency of approximately 250 and 300 脳 伪-SiO₂, respectively. Charge constants d₃₃ of approximately 72 and 94 pm/V were obtained for RbPbCO₃F and CsPbCO₃F, respectively, through converse piezoelectric measurements. Electronic structure calculations indicate that the nonlinear optical response originates from the distorted PbO₆F₂ polyhedra, because of the even鈥搊dd parity mixing of the O 2p states with the nearly spherically symmetric 6s electrons of Pb²⁺. The degree of inversion symmetry breaking is quantified using a mode-polarization vector analysis and is correlated with cation size mismatch, from which it is possible to deduce the acentric properties of 3D alkali-metal fluorocarbonates.