Synthesis of 尾-Mg2C3: A Monoclinic High-Pressure Polymorph of Magnesium Sesquicarbide

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• 作者：Timothy A. Strobel ; Oleksandr O. Kurakevych ; Duck Young Kim ; Yann Le Godec ; Wilson Crichton ; J茅r茅my Guignard ; Nicolas Guignot ; George D. Cody ; Artem R. Oganov
• 刊名：Inorganic Chemistry
• 出版年：2014
• 出版时间：July 7, 2014
• 年：2014
• 卷：53
• 期：13
• 页码：7020-7027
• 全文大小：470K
• ISSN：1520-510X

文摘

A new monoclinic variation of Mg₂C₃ was synthesized from the elements under high-pressure (HP), high-temperature (HT) conditions. Formation of the new compound, which can be recovered to ambient conditions, was observed in situ using X-ray diffraction with synchrotron radiation. The structural solution was achieved by utilizing accurate theoretical results obtained from ab initio evolutionary structure prediction algorithm USPEX. Like the previously known orthorhombic Pnnm structure (伪-Mg₂C₃), the new monoclinic C2/m structure (尾-Mg₂C₃) contains linear C₃^{4鈥?/sup> chains that are isoelectronic with CO₂. Unlike 伪-Mg₂C₃, which contains alternating layers of C₃4鈥?/sup> chains oriented in opposite directions, all C₃4鈥?/sup> chains within 尾-Mg₂C₃ are nearly aligned along the crystallographic c-axis. Hydrolysis of 尾-Mg₂C₃ yields C₃H₄, as detected by mass spectrometry, while Raman and NMR measurements show clear C鈺怌 stretching near 1200 cm鈥? and 13C resonances confirming the presence of the rare allylenide anion.}