Department of Geosciences, Stony Brook University, Stony Brook, New York 11794, USA.
Phys Chem Chem Phys. 2013 May 28;15(20):7696-700. doi: 10.1039/c3cp50678a. Epub 2013 Apr 17.
Using ab initio evolutionary simulations, we explore the entire range of possible stoichiometries for the Mg-O system at pressures of up to 850 GPa. In addition to MgO, our calculations find that two extraordinary compounds MgO2 and Mg3O2 become thermodynamically stable at 116 GPa and 500 GPa, respectively. Detailed chemical bonding analysis shows large charge transfer in all magnesium oxides. MgO2 contains peroxide ions O-O, while non-nuclear electron density maxima play the role of anions in the electride compound Mg3O2. The latter compound is calculated to have a much narrower band gap compared to MgO and MgO2. We discuss the conditions under which MgO2 and Mg3O2 could exist in planetary interiors.
利用从头算演化模拟，我们在高达 850 GPa 的压力下探索了 Mg-O 体系所有可能的化学计量比。除了 MgO，我们的计算还发现两种特殊的化合物 MgO2 和 Mg3O2 在 116 GPa 和 500 GPa 时分别变得热力学稳定。详细的化学成键分析表明，所有的氧化镁中都有大量的电荷转移。MgO2 中含有过氧离子 O-O，而非核电子密度极大值在电离子化合物 Mg3O2 中充当阴离子的作用。与 MgO 和 MgO2 相比，后者化合物的带隙要窄得多。我们讨论了 MgO2 和 Mg3O2 在行星内部存在的条件。
