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First-Order Isostructural Phase Transition Induced by High Pressure in Fe(IO3)3
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2020-03-29 , DOI: 10.1021/acs.jpcc.0c02080 Akun Liang 1 , Saqib Rahman 2 , Hajra Saqib 3 , Placida Rodriguez-Hernandez 4 , Alfonso Muñoz 4 , Gwilherm Nénert 5 , Ibraheem Yousef 6 , Catalin Popescu 6 , Daniel Errandonea 1
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2020-03-29 , DOI: 10.1021/acs.jpcc.0c02080 Akun Liang 1 , Saqib Rahman 2 , Hajra Saqib 3 , Placida Rodriguez-Hernandez 4 , Alfonso Muñoz 4 , Gwilherm Nénert 5 , Ibraheem Yousef 6 , Catalin Popescu 6 , Daniel Errandonea 1
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The high-pressure (HP) behavior of Fe(IO3)3 was studied up to 35 GPa using powder X-ray diffraction, infrared micro-spectroscopy, and ab initio density-functional theory calculations. Fe(IO3)3 shows a pressure-induced structural phase transition at 15–22 GPa. Powder X-ray diffraction was employed to obtain the structure of the HP phase. This phase can be described by the same space group (P63) as the low-pressure phase but with a substantial different c/a ratio. This conclusion is supported by our computational simulations. The discovered phase transition involves a large volume collapse and a change in the coordination polyhedron of iodine, being a first-order transition. It also produces substantial changes in the infrared and Raman vibrational spectra. The pressure dependences of infrared and Raman phonon frequencies and unit-cell parameters have been obtained. A mode assignment is proposed for phonons based upon ab initio calculations. The bulk modulus of the two phases was obtained by fitting a Birch–Murnaghan equation of state to synchrotron X-ray powder diffraction data resulting in B0 = 55(2) GPa for the low-pressure phase and B0 = 73(9) GPa for the HP phase. Calculations gave B0 = 36(1) GPa and B0 = 48(3) GPa for the same phases, respectively. The results are compared with other iodates, in particular LiIO3, for which we have also performed density-functional theory calculations. A possible mechanism driving the observed phase transition will be discussed.
中文翻译：
Fe（IO 3）3中高压引起的一阶同构相变
使用粉末X射线衍射，红外显微光谱和从头算密度函数理论计算，研究了高达35 GPa的Fe（IO 3）3的高压（HP）行为。Fe（IO 3）3在15-22 GPa处显示出压力诱导的结构相变。用粉末X射线衍射获得HP相的结构。这个阶段可以用相同的空间群来描述（P 6 3）作为低压相，但c / a比却大不相同。我们的计算仿真支持了这一结论。发现的相变涉及大量的坍塌和碘的配位多面体的变化，这是一阶过渡。它还会在红外和拉曼振动光谱中产生很大的变化。已经获得了红外和拉曼声子频率与晶胞参数的压力相关性。提出了一种基于从头算式的声子模式分配方法。通过将Birch-Murnaghan状态方程与同步加速器X射线粉末衍射数据拟合，可以得到两相的体积模量，得出低压相的B 0 = 55（2）GPa和BHP阶段为0 = 73（9）GPa。计算得出相同相位的B 0 = 36（1）GPa和B 0 = 48（3）GPa。将结果与其他碘酸盐，特别是LiIO 3进行比较，对此我们也进行了密度泛函理论计算。将讨论驱动观察到的相变的可能机制。
更新日期：2020-04-24
中文翻译：
Fe（IO 3）3中高压引起的一阶同构相变
使用粉末X射线衍射，红外显微光谱和从头算密度函数理论计算，研究了高达35 GPa的Fe（IO 3）3的高压（HP）行为。Fe（IO 3）3在15-22 GPa处显示出压力诱导的结构相变。用粉末X射线衍射获得HP相的结构。这个阶段可以用相同的空间群来描述（P 6 3）作为低压相，但c / a比却大不相同。我们的计算仿真支持了这一结论。发现的相变涉及大量的坍塌和碘的配位多面体的变化，这是一阶过渡。它还会在红外和拉曼振动光谱中产生很大的变化。已经获得了红外和拉曼声子频率与晶胞参数的压力相关性。提出了一种基于从头算式的声子模式分配方法。通过将Birch-Murnaghan状态方程与同步加速器X射线粉末衍射数据拟合，可以得到两相的体积模量，得出低压相的B 0 = 55（2）GPa和BHP阶段为0 = 73（9）GPa。计算得出相同相位的B 0 = 36（1）GPa和B 0 = 48（3）GPa。将结果与其他碘酸盐，特别是LiIO 3进行比较，对此我们也进行了密度泛函理论计算。将讨论驱动观察到的相变的可能机制。
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