科研之友
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摘要
We present a systematic first-principles study of the structural and vibrational properties of perovskite-structure EuTiO3. Our calculated phonon spectrum of the high-symmetry cubic structural prototype shows strong M-and R-point instabilities, indicating a tendency to symmetry-lowering structural deformations composed of rotations and tilts of the oxygen octahedra. Subsequent explicit study of 14 different octahedral tilt-patterns showed that the I4/mcm, Imma, and R (3) over barc structures, all with antiferrodistortive rotations of the octahedra, have significantly lower total energy than the prototype Pm (3) over barm structure. We discuss the dynamical stability of these structures, and the influence of the antiferrodistortive structural distortions on the vibrational, optical, and magnetic properties of EuTiO3, in the context of recent unexplained experimental observations.
- 出版日期2012-3-26
