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<p>High-pressure Raman spectra of Al-rich phase D (Mg<sub>0.93</sub>Al<sub>0.70</sub>Si<sub>1.29</sub>O<sub>6</sub>H<sub>2.88</sub>) and pure-Mg phase D (Mg<sub>1.03</sub>Si<sub>1.71</sub>O<sub>6</sub>H<sub>3.05</sub>) were measured up to 20 GPa in diamond-anvil cells using argon as a pressure medium. The results show that the intensity of the major 777&#xa0;cm<sup>− 1</sup> band in the Raman spectra of the pure-Mg phase D exhibits a significant intensity reduction within the 18–20 GPa range during compression. However, this band displays a highly linear shift in the Raman spectra of the Al-rich phase D without notable decrease in intensity in the same pressure range. This implies that the pressure stability of the M2 octahedra in the Al-rich phase D is higher than that in the pure-Mg phase D due to the substitution of Al<sup>3+</sup> for Si<sup>4+</sup>. The major OH band at about 2900&#xa0;cm<sup>− 1</sup> in the Raman spectra of the pure-Mg phase D sample shifts continuously toward higher frequencies with increasing pressure due to the pressure-induced transition from straight H bonds to bent ones. Whereas, this transition occurs at pressures above 10 GPa in the Al-rich phase D, indicating that Al<sup>3+</sup> substitution in the crystal structure of phase D can also alter the high-pressure response of hydroxyl ion.</p>

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High-pressure Raman spectroscopy of Al-rich and pure-Mg phase D

  • 期刊论文

  • 发表日期：

    2025年3月13日

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  • Chaowen Xu,
  • Li Zhang,
  • Xiaofeng Lu,
  • Yanhao Lin,
  • Shuo Qu,
  • Shuchang Gao,
  • Fengxia Sun,
  • Ying Li

摘要

High-pressure Raman spectra of Al-rich phase D (Mg0.93Al0.70Si1.29O6H2.88) and pure-Mg phase D (Mg1.03Si1.71O6H3.05) were measured up to 20 GPa in diamond-anvil cells using argon as a pressure medium. The results show that the intensity of the major 777 cm− 1 band in the Raman spectra of the pure-Mg phase D exhibits a significant intensity reduction within the 18–20 GPa range during compression. However, this band displays a highly linear shift in the Raman spectra of the Al-rich phase D without notable decrease in intensity in the same pressure range. This implies that the pressure stability of the M2 octahedra in the Al-rich phase D is higher than that in the pure-Mg phase D due to the substitution of Al3+ for Si4+. The major OH band at about 2900 cm− 1 in the Raman spectra of the pure-Mg phase D sample shifts continuously toward higher frequencies with increasing pressure due to the pressure-induced transition from straight H bonds to bent ones. Whereas, this transition occurs at pressures above 10 GPa in the Al-rich phase D, indicating that Al3+ substitution in the crystal structure of phase D can also alter the high-pressure response of hydroxyl ion.