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首页> 外文期刊>Physical review >Phonon quarticity induced by changes in phonon-tracked hybridization during lattice expansion and its stabilization of rutile TiO_2
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Phonon quarticity induced by changes in phonon-tracked hybridization during lattice expansion and its stabilization of rutile TiO_2

机译：晶格扩展过程中声子跟踪杂交的变化引起的声子四次性及其金红石型TiO_2的稳定

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摘要

Although the rutile structure of TiO_2 is stable at high temperatures, the conventional quasiharmonic approximation predicts that several acoustic phonons decrease anomalously to zero frequency with thermal expansion, incorrectly predicting a structural collapse at temperatures well below 1000 K. Inelastic neutron scattering was used to measure the temperature dependence of the phonon density of states (DOS) of rutile TiO_2 from 300 to 1373 K. Surprisingly, these anomalous acoustic phonons were found to increase in frequency with temperature. First-principles calculations showed that with lattice expansion, the potentials for the anomalous acoustic phonons transform from quadratic to quartic, stabilizing the rutile phase at high temperatures. In these modes, the vibrational displacements of adjacent Ti and O atoms cause variations in hybridization of 3d electrons of Ti and 2p electrons of O atoms. With thermal expansion, the energy variation in this "phonon-tracked hybridization" flattens the bottom of the interatomic potential well between Ti and O atoms, and induces a quarticity in the phonon potential.
机译：尽管TiO_2的金红石结构在高温下是稳定的，但传统的准谐波近似预测，随着热膨胀，几个声子会异常降低至零频率，错误地预测了远低于1000 K的温度下的结构坍塌。非弹性中子散射被用于测量金红石型TiO_2的声子态密度（DOS）在300到1373 K之间与温度有关。令人惊讶的是，发现这些异常声声子的频率随温度增加。第一性原理计算表明，随着晶格扩展，异常声子的势能从二次变为四次，从而在高温下稳定了金红石相。在这些模式下，相邻的Ti和O原子的振动位移引起Ti的3d电子和O原子的2p电子的杂化变化。随着热膨胀，这种“声子跟踪的杂化”中的能量变化使Ti和O原子之间的原子间势阱底部变平，并引起声子势的四次性。

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  • 来源
    《Physical review》 |2015年第5期|054304.1-054304.7|共7页
  • 作者

    Tian Lan; C. W. Li; O. Hellman; D. S. Kim; J. A. Munoz; H. Smith; D. L. Abernathy; B. Fultz;

  • 作者单位

    Department of Applied Physics and Materials Science, California Institute of Technology, Pasadena, California 91125, USA;

    Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA;

    Department of Applied Physics and Materials Science, California Institute of Technology, Pasadena, California 91125, USA;

    Department of Applied Physics and Materials Science, California Institute of Technology, Pasadena, California 91125, USA;

    Department of Applied Physics and Materials Science, California Institute of Technology, Pasadena, California 91125, USA;

    Department of Applied Physics and Materials Science, California Institute of Technology, Pasadena, California 91125, USA;

    Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA;

    Department of Applied Physics and Materials Science, California Institute of Technology, Pasadena, California 91125, USA;

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  • 正文语种 eng
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  • 关键词

    anharmonic lattice modes; thermal properties of crystalline solids;

    机译：非调和晶格模式结晶固体的热性质;

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