Milton Katherine L, Durrant Thomas R, Cobos Freire Teofilo, Shluger Alexander L
London Center for Nanotechnology, University College London, Gower Street, London WC1E 6BT, UK.
Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK.
Materials (Basel). 2023 Feb 7;16(4):1382. doi: 10.3390/ma16041382.
α-cristobalite (α-C) is a polymorph of silica, mainly found in space exploration and geochemistry research. Due to similar densities, α-C is often used as a proxy for amorphous SiO2, particularly in computer simulations of SiO2 surfaces and interfaces. However, little is known about the properties of α-C and its basic oxygen defects. Using density functional theory (DFT) simulations we provide a comprehensive report on the properties of perfect structure and oxygen vacancies in α-C. The calculated properties of α-C are compared with those of the better-characterized α-quartz (α-Q). Our results demonstrated that the positively charged O vacancy in α-C is most stable in the dimer configuration, in contrast to α-Q, which favors the puckered configuration. A back-projected configuration was also predicted in both polymorphs. We calculated the optical transition energies and isotropic hyperfine constants for O vacancies in both α-Q and α-C, and compared our findings with the results of previous studies and experiments. This work, thus, offers one of the first in-depth investigations of the properties of oxygen vacancies in α-C.
α-方石英（α-C）是二氧化硅的一种多晶型物，主要存在于太空探索和地球化学研究中。由于密度相似，α-C常被用作非晶态SiO₂的替代物，特别是在SiO₂表面和界面的计算机模拟中。然而，人们对α-C的性质及其基本氧缺陷知之甚少。利用密度泛函理论（DFT）模拟，我们提供了一份关于α-C完美结构和氧空位性质的综合报告。将计算得到的α-C性质与表征更完善的α-石英（α-Q）的性质进行了比较。我们的结果表明，与倾向于褶皱构型的α-Q不同，α-C中带正电的氧空位在二聚体构型中最稳定。在这两种多晶型物中还预测了一种反投影构型。我们计算了α-Q和α-C中氧空位的光学跃迁能量和各向同性超精细常数，并将我们的发现与先前的研究和实验结果进行了比较。因此，这项工作首次对α-C中氧空位的性质进行了深入研究。
