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首页> 外文期刊>Journal of Physics, D. Applied Physics: A Europhysics Journal >Investigation of structural, vibrational and ferroic properties of AgNbO3 at room temperature using neutron diffraction, Raman scattering and density-functional theory
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Investigation of structural, vibrational and ferroic properties of AgNbO3 at room temperature using neutron diffraction, Raman scattering and density-functional theory

机译：利用中子衍射，拉曼散射和密度泛函理论研究AgNbO3在室温下的结构，振动和铁磁性

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摘要

We perform a comprehensive study of the structural, lattice dynamical and ferroic properties of the room temperature phase of AgNbO3 using a combination of neutron diffraction, Raman spectroscopy and first-principles density functional theory. The Rietveld analysis of neutron diffraction data indicates that AgNbO3 at room temperature crystallizes in an orthorombic structure with noncentrosymmetric Pmc2(1) space group symmetry. The zone-center phonon mode frequencies of Pmc2(1) and Pbcm phases of AgNbO3 are computed and are found to be in good agreement with experimentally obtained Raman mode frequencies. Computed frequencies for both space groups are found to be very close. However, computed modes with frequencies 488 and 846 cm(-1) are found to be Raman-active for the Pmc2(1) phase while Raman inactive for Pbcm phase. The computed potential energy surfaces and Born effective charges of the ions suggest that the primary contribution to ferroic properties of AgNbO3 come from Nb and O ions only. Furthermore the calculated potential energy profiles suggest competing ferroic and antiferrodistortive instabilities in AgNbO3 are primarily due to the off-centering of Nb ions and rotations of NbO6 octahedra, respectively.
机译：我们结合中子衍射，拉曼光谱和第一原理密度泛函理论对AgNbO3室温相的结构，晶格动力学和铁素体性质进行了全面研究。中子衍射数据的Rietveld分析表明，室温下AgNbO3在具有非中心对称Pmc2（1）空间群对称性的正交结构中结晶。计算了Pmc2（1）的区域中心声子模频率和AgNbO3的Pbcm相，发现与实验获得的拉曼模频率非常吻合。发现两个空间组的计算频率非常接近。但是，发现频率为488和846 cm（-1）的计算模式对Pmc2（1）相具有拉曼活性，而对Pbcm相则不具有拉曼活性。计算出的离子的势能面和Born有效电荷表明，AgNbO3对铁性能的主要贡献仅来自Nb和O离子。此外，计算出的势能曲线表明，AgNbO3中竞争性的铁性和反铁畸变的不稳定性主要是由于Nb离子偏心和NbO6八面体的旋转。

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