Physics Department, Auburn University, 206 Allison Lab, Auburn University, Auburn, AL 36849, USA.
Proc Natl Acad Sci U S A. 2010 Mar 9;107(10):4539-43. doi: 10.1073/pnas.0907194107. Epub 2010 Feb 22.
Thermal conductivity of the Earth's lower mantle greatly impacts the mantle convection style and affects the heat conduction from the core to the mantle. Direct laboratory measurement of thermal conductivity of mantle minerals remains a technical challenge at the pressure-temperature (P-T) conditions relevant to the lower mantle, and previously estimated values are extrapolated from low P-T data based on simple empirical thermal transport models. By using a numerical technique that combines first-principles electronic structure theory and Peierls-Boltzmann transport theory, we predict the lattice thermal conductivity of MgO, previously used to estimate the thermal conductivity in the Earth, at conditions from ambient to the core-mantle boundary (CMB). We show that our first-principles technique provides a realistic model for the P-T dependence of lattice thermal conductivity of MgO at conditions from ambient to the CMB, and we propose thermal conductivity profiles of MgO in the lower mantle based on geotherm models. The calculated conductivity increases from 15 -20 W/K-m at the 670 km seismic discontinuity to 40 -50 W/K-m at the CMB. This large depth variation in calculated thermal conductivity should be included in models of mantle convection, which has been traditionally studied based on the assumption of constant conductivity.
下地幔的热导率对地幔对流方式有很大影响，并影响从地核到地幔的热传导。在与下地幔相关的压力-温度（P-T）条件下，直接测量地幔矿物的热导率仍然是一个技术挑战，之前的估计值是根据简单的经验热输运模型从低 P-T 数据外推得到的。我们使用一种将第一性原理电子结构理论和佩尔斯-玻尔兹曼输运理论相结合的数值技术，预测了 MgO 的晶格热导率，该热导率之前被用于估计地球的热导率，预测范围从环境条件到地核-地幔边界（CMB）。我们表明，我们的第一性原理技术为从环境条件到 CMB 的 MgO 晶格热导率的 P-T 依赖性提供了一个现实的模型，并且我们基于地热模型提出了下地幔中 MgO 的热导率分布。计算出的电导率从 670km 地震不连续处的 15-20 W/K-m 增加到 CMB 处的 40-50 W/K-m。这种计算出的热导率在深度上的大变化应该包含在地幔对流模型中，而传统上基于恒定电导率的假设来研究地幔对流模型。
