First-principles calculations of elasticity of minerals at high temperature and pressure

The elasticity of minerals at high temperature and pressure （PT） is critical for constraining the composition and temperature of the Earth＇s interior and understand better the deep water cycle and the dynamic Earth. First-principles calcula- tions without introducing any adjustable parameters, whose results can be comparable to experimental data, play a more and more important role in investigating the elasticity of minerals at high PT mainly because of （1） the quick increasing of computational powers and （2） advances in method. For example, the new method reduces the computation loads to one-tenth of the traditional method with the comparable precise as the traditional method. This is extraordinarily helpful because first-principles calculations of the elasticity of minerals at high PT are extremely time-consuming. So far the elasticity of most of lower mantle minerals has been investigated in detail. We have good idea on the effect of temperature, pressure, and iron concentration on elasticity of main minerals of the lower mantle and the unusual softening in bulk modulus by the spin crosso- ver of iron in ferropericlase. With these elastic data the lower mantle has been constrained to have 10-15 wt% ferropericlase, which is sufficient to generate some visible effects of spin crossover in seismic tomography. For example, the spin crossover causes that the temperature sensitivity of P wave at the depth of -1700 km is only a fraction of that at the depth of -2300 kin. The disruptions of global P wave structure and of P wave image below hotspots such as Hawaii and Iceland at similar depth are in consistence with the spin crossover effect of iron in ferropericlase. The spin crossover, which causes anomalous ther- modynamic properties of ferropericlase, has also been found to play a control role for the two features of the large low shear velocity provinces （LLSVPs）： the sharp edge and high elevation up to 1000 km above core-mantle boundary. All these results clearly suggest the spin crossover of iron in the lower mantle. The theoretical investigations for the elasticity of minerals at the upper mantle and water effect on elasticity of minerals at the mantle transition zone and subducting slab have also been con- ducted extensively. These researches are critical for understanding better the composition of the upper mantle and water dis- tribution and transport in the Earth＇s mantle. Most of these were static calculations, which did not include the vibrational （temperature） effect on elasticity, although temperature effect on elasticity is basic because of high temperature at the Earth＇s interior and huge temperature difference between the ambient mantle and the subducting slab. Including temperature effect on elasticity of minerals should be important future work. New method developed is helpful for these directions. The elasticity of iron and iron-alloy with various light elements has also been calculated extensively. However, more work is necessary in order to meet the demand for constraining the types and amount of light elements at the Earth＇s core. Keywords Mantle temperature, Mantle composition, Composition of Earth＇s core, Ab initio method

在高温度和压力(磅) 的矿物质的弹性为抑制地球内部的作文和温度是批评的并且更好理解深水周期和动态地球。没有介绍任何可调节的参数的第一原则的计算，其结果能比得上试验性的数据，在因为主要，在高磅调查矿物质的弹性起一个越来越重要的作用(1 ) 计算力量的快增加并且(2 ) 在方法进展。例如，新方法把计算负担归结为传统的方法的十分之一与可比较象传统的方法精确。因为在高磅的矿物质的弹性的第一原则的计算是极其费时间的，这是非常地有用的。到目前为止，大多数更低的披风矿物质的弹性详细被调查了。我们在更低的披风并且大批的不平常的弄软的主要矿物质的弹性上在温度，压力，和铁集中的效果上有好主意由在 ferropericlase 的铁的旋转转线路的模量。与这些有弹性的数据，更低的披风被抑制了有 10-15 wt% ferropericlase，它是足够的在地震断层摄影术产生旋转转线路的一些可见效果。例如，旋转转线路引起在 1700 km 仅仅是的 ~ 的深度的 P 波浪的温度敏感很少的那在 ~ 的深度 2300 km。全球 P 波浪结构并且在象在类似的深度的夏威夷和冰岛那样的热点下面的 P 波浪图象的混乱在有在 ferropericlase 的铁的旋转转线路效果的坚固性。旋转转线路，引起 ferropericlase 的异常热力学的性质，也被发现了为二个特征起一个控制作用大低砍速度省(LLSVP ) ：锋利的边和高举起直到在核心披风边界上面的 1000 km。所有这些结果清楚地在更低的披风建议铁的旋转转线路。为在在披风转变地区和 subducting 平板的矿物质的弹性上的上面的披风和水效果的矿物质的弹性的理论调查也广泛地被进行了。这些研究为更好在地球披风理解上面的披风和水分发和运输的作文是批评的。这些中的大多数是静态的计算，它没包括震动(温度) 在弹性上完成，尽管因为高温度，弹性上的温度效果是基本的。在矿物质的弹性上包括温度效果应该是重要未来工作。开发的新方法对这些方向有用。有各种各样的轻元素的铁和铁合金的弹性也广泛地被计算了。然而，更多的工作是必要的以便为在地球核心抑制轻元素的类型和数量遇见需求。