Badro James, Côté Alexander S, Brodholt John P
Institut de Physique du Globe de Paris, Sorbonne Paris Cité-Université Paris Diderot, Unité Mixte de Recherche 7154, Centre National de la Recherche Scientifique, 75005 Paris, France;Earth and Planetary Sciences Laboratory, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland; and
Institut de Physique du Globe de Paris, Sorbonne Paris Cité-Université Paris Diderot, Unité Mixte de Recherche 7154, Centre National de la Recherche Scientifique, 75005 Paris, France;Department of Earth Sciences, University College London, London WC1E 6BT, United Kingdom.
Proc Natl Acad Sci U S A. 2014 May 27;111(21):7542-5. doi: 10.1073/pnas.1316708111. Epub 2014 May 12.
Earth's core is less dense than iron, and therefore it must contain "light elements," such as S, Si, O, or C. We use ab initio molecular dynamics to calculate the density and bulk sound velocity in liquid metal alloys at the pressure and temperature conditions of Earth's outer core. We compare the velocity and density for any composition in the (Fe-Ni, C, O, Si, S) system to radial seismological models and find a range of compositional models that fit the seismological data. We find no oxygen-free composition that fits the seismological data, and therefore our results indicate that oxygen is always required in the outer core. An oxygen-rich core is a strong indication of high-pressure and high-temperature conditions of core differentiation in a deep magma ocean with an FeO concentration (oxygen fugacity) higher than that of the present-day mantle.
地核的密度低于铁，因此它必定含有诸如硫、硅、氧或碳等“轻元素”。我们使用从头算分子动力学方法来计算液态金属合金在地球外核的压力和温度条件下的密度和体声速。我们将（铁 - 镍、碳、氧、硅、硫）体系中任意成分的速度和密度与径向地震学模型进行比较，找出了一系列符合地震学数据的成分模型。我们没有找到符合地震学数据的无氧成分，因此我们的结果表明外核中总是需要氧。富氧的地核有力地表明，在一个深部岩浆海洋中，地核分异的高压和高温条件下，其氧化亚铁浓度（氧逸度）高于现今的地幔。
