What is it about?
Ferrierite is a porous material of great relevance in mineralogy, industry, and technology. Its structure was subject of a debate lasting several decades. Diffraction experiments suggested that ferrierite had straight bond angles at elevated temperatures. On the other hand, straight bonds are energetically unfavourable and should not exist in crystalline silicates at normal conditions. By studying this material with molecular dynamics at high temperature, we show that truly linear bond angles do not actually exist in ferrierite: the structure is flexible, and the angles can easily bend. Hence, at high temperature, ferrierite has straigth angles only on average. When viewed instantaneously, its symmetry is lower, and bending of the angles occurs extremely fast.
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Why is it important?
The flexibility of the apparently flat linkages of ferrierite here discovered might play an important role for the incorporation of molecules in its pores - a process which occurs in geological processes and industrial applications alike.
Perspectives
In perspective, the flexibility of the flat bond angles of ferrierite and other zeolites might help us to better understand the transformations of silicate minerals under the elevated pressures and temperatures typical of Earth's mantle or extraterrestrial environments.
Gloria Tabacchi
university of insubria
Read the Original
This page is a summary of: Computer modeling of apparently straight bond angles: The intriguing case of all-silica ferrierite, American Mineralogist, November 2019, Mineralogical Society of America,
DOI: 10.2138/am-2019-6951.
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