Zhang Shoutao, Li Fei, Xu Haiyang, Yang Guochun
Centre for Advanced Optoelectronic Functional Materials Research and Key Laboratory for UV Light-Emitting Materials and Technology of Ministry of Education, Northeast Normal University , Changchun 130024, China.
State Key Laboratory of Superhard Materials, Jilin University , Changchun 130012, China.
Inorg Chem. 2017 May 1;56(9):5233-5238. doi: 10.1021/acs.inorgchem.7b00365. Epub 2017 Apr 11.
Beryllium oxides, at ambient pressure, have been extensively studied due to their unique chemical bonds and applications. However, the long-desirable target beryllium peroxide (BeO) has not been reported, thus far. Currently, the application of pressure has become a powerful tool in finding unusual stoichiometric compounds with exotic properties. Here, swarm structural searches in combination with first-principles calculations disclosed that the reaction of BeO and oxygen, at pressures above 89.6 GPa, yields BeO. Interestingly, this reaction pressure is lower than the phase transition pressure (106 GPa) of pure BeO. BeO crystallizes in FeS-type structure, whose remarkable feature is that it contains peroxide group (O) with an O-O distance of 1.40 Å at 100 GPa. Notably, O is maintained in the pressure range of 89.6-300 GPa. The chemical bonding analysis shows that the uniformly distributed ionic Be-O and covalent O-O bonding network plays a key role in determining its structural stability. BeO is a direct band gap nonmetal, and its band gap becomes larger with increase of pressure, which is in sharp contrast with BaO. Moreover, phase diagram of Be-O binary compounds with various BeO (x = 1-3, y = 1-6) compositions at pressures of up to 300 GPa was reliably built. Our results are also important for enriching the understanding of beryllium oxides.
在常压下，氧化铍因其独特的化学键和应用而受到广泛研究。然而，长期以来备受期待的过氧化铍（BeO₂）迄今尚未见报道。目前，压力的应用已成为发现具有奇异性质的非常规化学计量化合物的有力工具。在此，通过群结构搜索结合第一性原理计算发现，在压力高于89.6 GPa时，BeO与氧气反应生成BeO₂。有趣的是，该反应压力低于纯BeO的相变压力（106 GPa）。BeO₂以FeS型结构结晶，其显著特征是在100 GPa时它含有过氧基团（O₂²⁻），O - O距离为1.40 Å。值得注意的是，在89.6 - 300 GPa的压力范围内O₂²⁻得以保持。化学键分析表明，均匀分布的离子型Be - O和共价型O - O键网络在决定其结构稳定性方面起关键作用。BeO₂是一种直接带隙非金属，其带隙随压力增加而增大，这与BaO₂形成鲜明对比。此外，还可靠地构建了在高达300 GPa压力下具有各种BeOₓ（x = 1 - 3，y = 1 - 6）组成的Be - O二元化合物的相图。我们的结果对于丰富对氧化铍的认识也具有重要意义。
