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首页> 外文期刊>Acta Crystallographica, Section B. Structural science, crystal engineering and materials >Ferroelectric glycine silver nitrate: a single-crystal neutron diffraction study
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Ferroelectric glycine silver nitrate: a single-crystal neutron diffraction study

机译:铁电甘氨酸硝酸银:单晶中子衍射研究

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摘要

Protonated crystals of glycine silver nitrate (C_4H_(10)Ag_2N_4O_(10)) undergo a displacive kind of structural phase transition to a ferroelectric phase at 218 K. Glycine silver nitrate (GSN) is a light-sensitive crystal. Single-crystal X-ray diffraction investigations are difficult to perform on these crystals due to the problem of crystal deterioration on prolonged exposure to X- rays. To circumvent this problem, single-crystal neutron diffraction investigations were performed. We report here the crystal structure of GSN in a ferroelectric phase. The final R value for the refined structure at 150 K is 0.059. A comparison of the low-temperature structure with the room- temperature structure throws some light on the mechanism of the structural phase change in this crystal. We have attempted to explain the structural transition in GSN within the framework of the vibronic theory of ferroelectricity, suggesting-that the second-order Jahn-Teller (pseudo-Jahn- Teller) behavior of the Ag+ ion in GSN leads to structural distortion at low temperature (218 K).
机译:甘氨酸硝酸银(C_4H_(10)Ag_2N_4O_(10))的质子化晶体在218 K下发生位移型结构相转变为铁电相。甘氨酸硝酸银(GSN)是一种光敏晶体。由于长时间暴露于X射线会导致晶体劣化的问题,因此难以对这些晶体进行单晶X射线衍射研究。为了解决这个问题,进行了单晶中子衍射研究。我们在这里报告铁电相中GSN的晶体结构。精制结构在150 K时的最终R值为0.059。低温结构与室温结构的比较为该晶体中结构相变的机理提供了一些启示。我们试图在铁电振动理论的框架内解释GSN中的结构转变,这表明-GSN中Ag +离子的二阶Jahn-Teller(pseudo-Jahn-Teller)行为会导致低位结构畸变温度(218 K)。

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