The iron spin crossover in (Mg_1-xFe_x)O ferropericlase causes changes to its physical properties that are expected to affect seismic velocities in Earth's lower mantle. We present new time-resolved pressure-volume measurements of iron-rich ferropericlase (x_Fe = 0.40, 0.59) and combine the results with literature data with x_Fe = 0.04–0.6 to investigate the dependence of ferropericlase elastic properties on iron content. We infer the relationship between unit-cell volume, pressure and iron content directly from the data by training Mixture Density Networks and derive bulk modulus, density and bulk sound velocity from the outputs. This allows us to constrain the effect of the spin crossover on these properties and estimate their uncertainties for different iron contents. Our findings indicate that the spin crossover may significantly alter the physical properties of ferropericlase in iron-enriched regions in the lowermost mantle, with implications for the interpretation of seismic heterogeneities observed near the core-mantle boundary.

中文翻译：

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来自新实验和机器学习的铁含量-铁弹性特性在自旋交叉中的依赖性


（Mg_1-xFe_x）O 铁方镁石中的铁自旋交叉导致其物理性质发生变化，预计这将影响地球下地幔的地震速度。我们提出了富铁方镁石 （x_Fe = 0.40， 0.59） 的新时间分辨压力体积测量值，并将结果与 x_Fe = 0.04-0.6 的文献数据相结合，以研究铁方镁石弹性特性对铁含量的依赖性。我们通过训练混合物密度网络，直接从数据中推断出晶胞体积、压力和铁含量之间的关系，并从输出中得出体模量、密度和体声速。这使我们能够限制自旋交叉对这些特性的影响，并估计它们对不同铁含量的不确定性。我们的研究结果表明，自旋交叉可能会显着改变最下地幔中富铁区域铁方镁石的物理性质，这对解释在核-地幔边界附近观察到的地震非均质性产生影响。