Combined Theoretical and in Situ Scattering Strategies for Optimized Discovery and Recovery of High-Pressure Phases: A Case Study of the GaN–Nb2O5 System

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• 作者：William R. Woerner ; Guang-Rui Qian ; Artem R. Oganov ; Peter W. Stephens ; H. A. Naveen Dharmagunawardhane ; Alexandra Sinclair ; John B. Parise
• 刊名：Inorganic Chemistry
• 出版年：2016
• 出版时间：April 4, 2016
• 年：2016
• 卷：55
• 期：7
• 页码：3384-3392
• 全文大小：589K
• ISSN：1520-510X

文摘

The application of pressure in solid-state synthesis provides a route for the creation of new and exciting materials. However, the onerous nature of high-pressure techniques limits their utility in materials discovery. The systematic search for novel oxynitrides—semiconductors for photocatalytic overall water splitting—is a representative case where quench high-pressure synthesis is useful and necessary in order to obtain target compounds. We utilize state of the art crystal structure prediction theory (USPEX) and in situ synchrotron-based X-ray scattering to speed up the discovery and optimization of novel compounds using high-pressure synthesis. Using this approach, two novel oxynitride phases were discovered in the GaN–Nb₂O₅ system. The (Nb₂O₅)_0.84:(NbO₂)_0.32:(GaN)_0.82 rutile structured phase was formed at 1 GPa and 900 °C and gradually transformed to a α-PbO₂-related structure above 2.8 GPa and 1000 °C. The low-pressure rutile type phase was found to have a direct optical band gap of 0.84 eV and an indirect gap of 0.51 eV.