hide
Free keywords:
Atoms; Chemical bonds; Crystal atomic structure; Magnesium; Magnesium compounds; Silicon; Single crystals; Supramolecular chemistry, Atomic interactions; Cage compounds; Chemical bondings; Crystal structure determination; Diffraction tomography; High pressure high temperature; High-pressure synthesis; Synthesis optimization, Silicon compounds
Abstract:
The silicon-rich cage compound MgSi5 was obtained by high-pressure high-temperature synthesis. Initial crystal structure determination by electron diffraction tomography provided the basis for phase analyses in the process of synthesis optimization, finally facilitating the growth of single crystals suitable for X-ray diffraction experiments. The crystal structure of MgSi5 (space group Cmme, Pearson notation oS24, a=4.4868(2) Å, b=10.1066(5) Å, and c=9.0753(4) Å) constitutes a new type of framework of four-bonded silicon atoms forming Si15 cages enclosing the Mg atoms. Two types of smaller Si8 cages remain empty. The atomic interactions are characterized by two-center two-electron bonds within the silicon framework. In addition, there is evidence for multi-center Mg−Si bonding in the large cavities of the framework and for lone-pair-like interactions in the smaller empty voids. © 2019 Wiley-VCH Verlag GmbH Co. KGaA, Weinheim
