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Structures and Stability of Iron Halides at the Earth’s Mantle and Core Pressures: Implications for the Missing Halogen Paradox
ACS Earth and Space Chemistry ( IF 3.4 ) Pub Date : 2018-05-30 00:00:00 , DOI: 10.1021/acsearthspacechem.8b00034 XiangPo Du 1 , Ziwei Wang 2, 3 , Hongbo Wang 1 , Toshiaki Iitaka 4 , Yuanming Pan 5 , Hui Wang 1 , John S. Tse 1, 6
ACS Earth and Space Chemistry ( IF 3.4 ) Pub Date : 2018-05-30 00:00:00 , DOI: 10.1021/acsearthspacechem.8b00034 XiangPo Du 1 , Ziwei Wang 2, 3 , Hongbo Wang 1 , Toshiaki Iitaka 4 , Yuanming Pan 5 , Hui Wang 1 , John S. Tse 1, 6
Affiliation
The terrestrial abundance of heavy halogens Cl, Br, and I is depleted by approximately one order of magnitude relative to those predicted on the basis of their volatilities. One plausible explanation for this missing halogen paradox is their sequestration into the Earth’s core. Therefore, heavy halogens in the core may combine with the dominant element, Fe, to form iron halides that potentially exert important effects on the properties and dynamic evolution of the Earth’s inner core. In this study, stable iron halide phases have been predicted from first-principles structural searches at four pressures corresponding to those at the Earth’s mantle and core. At 360 GPa (corresponding to the inner core), the most stable iron chloride is CsCl-type FeCl, supporting the hypothesis that light-element impurities can stabilize the body-centered cubic Fe structure. At pressures of the Earth’s core, it is also observed that the chemical nature of iodine changes from an electron acceptor to an electron donor. This change results in an enhancement of the stability and the formation of a novel Fe2I compound containing a Fe–I framework with linear Fe chains intercalated in the open channels. Thus, the role of pressure in determining the stoichiometry of stable high-pressure halides is demonstrated by our theoretical calculations. These findings suggest the possibility of thermodynamic stability of iron halides in the assemblage in the Earth’s inner core.
中文翻译:
地球地幔和核心压力下卤化铁的结构和稳定性:对缺失卤素悖论的影响
相对于根据其挥发性预测的那些,重卤素Cl,Br和I的陆地丰度大约减少了一个数量级。对于这种缺失的卤素悖论,一个合理的解释是它们被螯合到了地球的核心。因此,核心中的重卤素可能与占主导地位的元素Fe结合形成卤化铁,可能对地球内核的特性和动态演化产生重要影响。在这项研究中,通过第一性原理的结构搜索在对应于地球地幔和核心压力的四个压力下,预测了稳定的卤化铁相。在360 GPa(对应于内核)下,最稳定的氯化铁是CsCl型FeCl,支持轻质杂质可以稳定以人体为中心的立方铁结构的假说。在地球核心的压力下,还观察到碘的化学性质从电子受体变为电子供体。这种变化导致稳定性的增强和新型铁的形成。2 I化合物,其中包含带有在开放通道中插入的线性Fe链的FeI骨架。因此,我们的理论计算证明了压力在确定稳定的高压卤化物的化学计量中的作用。这些发现表明,在地球内核中,卤化铁具有热力学稳定性。
更新日期:2018-05-30
中文翻译:
地球地幔和核心压力下卤化铁的结构和稳定性:对缺失卤素悖论的影响
相对于根据其挥发性预测的那些,重卤素Cl,Br和I的陆地丰度大约减少了一个数量级。对于这种缺失的卤素悖论,一个合理的解释是它们被螯合到了地球的核心。因此,核心中的重卤素可能与占主导地位的元素Fe结合形成卤化铁,可能对地球内核的特性和动态演化产生重要影响。在这项研究中,通过第一性原理的结构搜索在对应于地球地幔和核心压力的四个压力下,预测了稳定的卤化铁相。在360 GPa(对应于内核)下,最稳定的氯化铁是CsCl型FeCl,支持轻质杂质可以稳定以人体为中心的立方铁结构的假说。在地球核心的压力下,还观察到碘的化学性质从电子受体变为电子供体。这种变化导致稳定性的增强和新型铁的形成。2 I化合物,其中包含带有在开放通道中插入的线性Fe链的FeI骨架。因此,我们的理论计算证明了压力在确定稳定的高压卤化物的化学计量中的作用。这些发现表明,在地球内核中,卤化铁具有热力学稳定性。