Key Laboratory of Earth and Planetary Physics, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China.
Phys Chem Chem Phys. 2019 Jan 21;21(3):1009-1013. doi: 10.1039/c8cp06702c. Epub 2018 Dec 7.
Bridgmanite, a high temperature and pressure form of MgSiO, is believed to be Earth's most abundant mineral and responsible for the observed seismic anisotropy in the mantle. Little is known about surfaces of bridgmanite but knowledge of the most stable surface terminations is important for understanding various geochemical processes as well as likely slip planes. A density functional theory based thermodynamic approach is used here to establish the range of stability of bridgmanite as well as possible termination structures of the (001), (010), (100) and (011) surfaces as a function of the chemical potential of oxygen and magnesium. The vibrational contribution to the Gibbs free energy is found to be essential for obtaining a stability region of bridgmanite in the phase diagram. The most stable surface termination of bridgmanite varies between three different atomic structures depending on the chemical potential of oxygen and magnesium. The results presented provide a basis for further theoretical studies of the chemical processes on bridgmanite surfaces in the Earth's mantle and slip plane analysis.
尖晶石，一种高温高压形式的 MgSiO，被认为是地球上最丰富的矿物质，也是地幔中观察到地震各向异性的原因。关于尖晶石的表面知之甚少，但了解最稳定的表面终止形式对于理解各种地球化学过程以及可能的滑移面非常重要。这里使用基于密度泛函理论的热力学方法来确定尖晶石的稳定范围以及（001）、（010）、（100）和（011）表面的可能终止结构，作为氧和镁化学势的函数。发现振动对吉布斯自由能的贡献对于在相图中获得尖晶石的稳定区域是必不可少的。尖晶石最稳定的表面终止取决于氧和镁的化学势，在三种不同的原子结构之间变化。所提出的结果为进一步研究地幔中尖晶石表面的化学过程和滑移面分析提供了基础。
