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首页> 外文期刊>Physica, B. Condensed Matter >Vibrational properties and phonon anharmonicity in ZnS_(1-x)Se_x: Inelastic neutron scattering, Raman scattering, X-ray diffraction measurements and lattice dynamical studies
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Vibrational properties and phonon anharmonicity in ZnS_(1-x)Se_x: Inelastic neutron scattering, Raman scattering, X-ray diffraction measurements and lattice dynamical studies

机译：ZnS_（1-x）Se_x的振动性质和声子非谐性：非弹性中子散射，拉曼散射，X射线衍射测量和晶格动力学研究

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Inelastic neutron scattering, Raman and X-ray diffraction measurements coupled with lattice dynamical calculations (employing a semi-empirical transferable potential model) have been carried out to gain a detailed understanding of the peculiar vibrational spectrum exhibited by the mixed crystal ZnS_(1-x)Se_x. Raman scattering measurements performed over a varying range of temperature (100-800 K) and pressure (up to 13 GPa) have confirmed that the additional mode observed in the spectra are visible over the entire range of temperature and pressure. Correlation of the individual motions of atoms (obtained from computed total and partial phonon density of states) with the inelastic neutron scattering measurements (carried out over the entire Brillouin zone) have then indicated that the existence of the additional mode in ZnS_(1-x)Se_x is due to the vibrations of the Se atom being in resonance with that of the S atom. Further, it has been shown that the presence of this additional mode can be tuned by varying the mass of the atom at the Se site. In addition, an analysis of bond-length distribution with increasing Se concentration have elucidated that bond-length spread is not responsible for the presence of the additional mode. An analysis of the peak shifts of the Raman modes with temperature and pressure indicate that the anharmonicity of the vibrational modes increases with increasing compositional disorder. This is attributed to the fact that increasing Se concentration gives rise to a distribution of bond-lengths in ZnS_(1-x)Se_x, which is responsible for this compositional disorder induced anharmonicity. Our computations have thus revealed that mass of the anion is responsible for the presence of additional mode while bond-length distribution gives rise to the existence of compositional disorder induced anharmonicity in ZnS_(1-x)Se_x. Further, it is observed that the contribution of explicit anharmonicity to the total anharmonicity becomes dominant at higher temperatures. This compound also exhibits negative thermal expansion at low temperatures as obtained from our X-ray diffraction measurements as a function of temperature (10-800 K).
机译：已经进行了非弹性中子散射，拉曼和X射线衍射测量以及晶格动力学计算（采用半经验可转移势能模型），以详细了解混合晶体ZnS_（1-x ）性别。在温度（100-800 K）和压力（最高13 GPa）的变化范围内进行的拉曼散射测量已确认，在光谱中观察到的其他模式在温度和压力的整个范围内都是可见的。原子的单个运动（从计算的总声子密度和部分声子态获得）与非弹性中子散射测量值（在整个布里渊区中进行的测量）之间的相关性表明，ZnS_（1-x ）Se_x是由于Se原子的振动与S原子的振动共振引起的。此外，已经表明，可以通过改变Se位点处原子的质量来调节该附加模式的存在。此外，随着硒浓度的增加，键长分布的分析表明，键长扩展与附加模式的存在无关。对拉曼模式的峰值位移随温度和压力的分析表明，振动模式的非谐性随组成无序的增加而增加。这归因于这样一个事实，即硒浓度的增加会导致ZnS_（1-x）Se_x中键长的分布，这是造成这种成分紊乱引起的非谐性的原因。因此，我们的计算表明，阴离子的质量是导致附加模态存在的原因，而键长分布则导致ZnS_（1-x）Se_x中存在由成分无序引起的非谐性。此外，观察到，在较高温度下，显式非谐性对总非谐性的贡献变得占主导。根据我们的X射线衍射测量，该化合物在低温下还表现出负热膨胀，该温度是温度（10-800 K）的函数。

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