The stability, structure, and elastic properties of pyrite‐type (FeS₂ structured) FeO₂H were determined using density functional theory‐based computations with an internally consistent Coulombic self‐interaction term (U_eff). The properties of pyrite‐type FeO₂H are compared to that of pyrite‐type AlO₂H, with which it likely forms a solid solution at high temperature, as well as the respective lower pressure CaCl₂‐type polymorphs of both endmembers: ϵ‐FeOOH and δ‐AlOOH. Due to substantial differences in the CaCl₂‐type → pyrite‐type structural transition pressures of these endmembers, the stabilities of the (Al,Fe)O₂H solid solution polymorphs are anticipated to be compositionally driven at lower mantle pressures. As the geophysical properties of (Al,Fe)OOH are structurally dependant, interpretations regarding the contribution of pyrite‐type FeO₂H to seismically observed features must take into account the importance of this broad phase loop. With this in mind, Fe‐rich pyrite‐type (Al,Fe)OOH may coexist with Al‐dominant CaCl₂‐type δ‐(Al,Fe)OOH in the deep Earth. Furthermore, pyrite‐type (Al_0.5–0.6,Fe_0.4–0.5)O₂H can reproduce the reduced compressional and shear velocities characteristic of seismically observed ultra low velocity zones in the Earth's lowermost mantle while Al‐dominant but Fe‐bearing CaCl₂‐type δ‐(Al,Fe)OOH may contribute to large low shear velocity provinces.

中文翻译：

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基于第一性原理计算的黄铁矿型FeOOH-AlOOH系统的弹性特性

黄铁矿型（FeS ₂结构）FeO ₂ H的稳定性，结构和弹性性质是使用基于密度泛函理论的计算法（具有内部一致的库仑自相互作用项（U _eff））确定的。将黄铁矿型FeO ₂ H的特性与黄铁矿型AlO ₂ H的特性进行比较，在高温下它们可能形成固溶体，并且两个末端成员各自的低压CaCl ₂型多晶型物：ϵ -FeOOH和δ - AlOOH。由于CaCl _2的实质差异这些端构件的→型→黄铁矿型结构转变压力，预计（Al，Fe）O ₂ H固溶体多晶型物的稳定性在较低的地幔压力下受成分驱动。由于（Al，Fe）OOH的地球物理特性在结构上是依赖的，因此关于黄铁矿型FeO ₂ H对地震观测特征的贡献的解释必须考虑到这一宽相环的重要性。考虑到这一点，富铁黄铁矿型（Al，Fe）OOH可能与Al占主导地位的CaCl ₂型δ‐（Al，Fe）OOH共存。此外，黄铁矿型（Al _0.5–0.6，Fe _0.4–0.5）O ₂H可以重现地球最低地幔中地震观测到的超低速区的压缩速度和剪切速度特征，而Al占主导但含Fe的CaCl ₂型δ－（Al，Fe）OOH可能有助于形成大的低剪切速度省份。