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首页> 外文期刊>Physical review >Inelastic neutron scattering studies of phonon spectra, and simulations of pressure-induced amorphization in tungstates AWO_4 (A = Ba, Sr, Ca, and Pb)
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Inelastic neutron scattering studies of phonon spectra, and simulations of pressure-induced amorphization in tungstates AWO_4 (A = Ba, Sr, Ca, and Pb)

机译：声子光谱的非弹性中子散射研究，以及在钨态AWO_4（A = Ba，Sr，Ca和Pb）中压力诱导的非晶化的模拟

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摘要

Lattice dynamics and high-pressure phase transitions in AWO_4 (A = Ba, Sr, Ca, and Pb) have been investigated using inelastic neutron scattering experiments, ab initio density functional theory calculations, and extensive molecular dynamics simulations. The vibrational modes that are internal to WO_4 tetrahedra occur at the highest energies consistent with the relative stability of WO_4 tetrahedra. The neutron data and the ab initio calculations are found to be in excellent agreement. The neutron and structural data are used to develop and validate an interatomic potential model. The model is used for classical molecular dynamics simulations to study their response to high pressure. We have calculated the enthalpies of the scheelite and fergusonite phases as a function of pressure, which confirms that the scheelite to fergusonite transition is second order in nature. With increase in pressure, there is a gradual change in the AO_8 polyhedra, while there is no apparent change in the WO_4 tetrahedra. We found that all the four tungstates amorphize at high pressure. This is in good agreement with available experimental observations which show amorphization at around 45 GPa in BaWO_4 and 40 GPa in CaWO_4. Further molecular dynamics simulations at high pressure and high temperature indicate that application of pressure at higher temperature hastens the process of amorphization. On amorphization, there is an abrupt increase in the coordination of the W atom while the bisdisphenoids around the A atom are considerably distorted. The pair-correlation functions of the various atom pairs corroborate these observations. Our observations aid in predicting the pressure of amorphization in SrWO_4 and PbWO_4.
机译：使用非弹性中子散射实验，从头算密度函数理论计算以及广泛的分子动力学模拟，研究了AWO_4（A = Ba，Sr，Ca和Pb）中的晶格动力学和高压相变。 WO_4四面体内部的振动模式以与WO_4四面体的相对稳定性一致的最高能量出现。发现中子数据和从头算是非常一致的。中子和结构数据用于开发和验证原子间电势模型。该模型用于经典分子动力学模拟，以研究其对高压的响应。我们已经计算出白钨矿和白铁矿相的焓是压力的函数，这证实白钨石到白铁矿的过渡本质上是二阶的。随着压力的增加，AO_8多面体逐渐发生变化，而WO_4四面体没有明显变化。我们发现所有四个钨酸盐都在高压下非晶化。这与现有的实验观察结果非常吻合，后者显示BaWO_4中约45 GPa和CaWO_4中约40 GPa非晶化。在高压和高温下的进一步分子动力学模拟表明，在高温下施加压力会加速非晶化过程。在非晶化过程中，W原子的配位突然增加，而A原子周围的双双蝶形化合物却大大变形。各种原子对的成对相关函数证实了这些观察结果。我们的观察有助于预测SrWO_4和PbWO_4中非晶化的压力。

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  • 来源
    《Physical review》 |2015年第9期|094304.1-094304.8|共8页
  • 作者

    Prabhatasree Goel; M. K. Gupta; R. Mittal; S. Rols; S. N. Achary; A. K. Tyagi; S. L. Chaplot;

  • 作者单位

    Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400085, India;

    Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400085, India;

    Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400085, India;

    Institut Laue-Langevin, BP 156, 38042 Grenoble Cedex 9, France;

    Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400085, India;

    Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400085, India;

    Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400085, India;

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  • 关键词

    general studies of phase transitions;

    机译：相变的一般研究;

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