Ab Initio Calculations of the Energy Dependence of Si鈥揙鈥揝i Angles in Silica and Ge鈥揙鈥揋e Angles in Germania Crystalline Systems

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• 作者：Colby J. Dawson ; Rebeca Sanchez-Smith ; Peter Rez ; Michael O鈥橩eeffe ; Michael M. J. Treacy
• 刊名：Chemistry of Materials
• 出版年：2014
• 出版时间：February 25, 2014
• 年：2014
• 卷：26
• 期：4
• 页码：1523-1527
• 全文大小：299K
• 年卷期：v.26,no.4(February 25, 2014)
• ISSN：1520-5002

文摘

Cristobalite is the only corner-sharing tetrahedral framework that can maintain perfectly regular SiO₄ tetrahedra throughout the entire 180掳 range of Si鈥揙鈥揝i angles. It is, thus, the ideal system for a study of the energy dependence of the Si鈥揙鈥揝i angle in a crystalline framework. Using the VASP first principles density functional code, we have derived energy versus Si鈥揙鈥揝i angle curves for pure silica and versus Ge鈥揙鈥揋e angles for pure germania models of cristobalite. In addition, the frameworks of quartz, tridymite, and the zeolites sodalite (SOD) and metavariscite (BCT) were studied. The range of angles with low energies is larger for silica, though the lowest-energy Ge鈥揙鈥揋e angle is always lower than the corresponding lowest-energy Si鈥揙鈥揝i angle in the same framework type. We discuss which framework types are possible for pure-silica and pure-germania based on a rigid tetrahedron model.