Polymorphic phase transition mechanism of compressed coesite

• Published in: Nature communications Vol. 6; no. 1; p. 6630
• Main Authors: Hu, Q Y, Shu, J-F, Cadien, A, Meng, Y, Yang, W G, Sheng, H W, Mao, H-K
• Format: Journal Article
• Language: English
• Published: England Nature Publishing Group 20.03.2015
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms7630

Silicon dioxide is one of the most abundant natural compounds. Polymorphs of SiO₂ and their phase transitions have long been a focus of great interest and intense theoretical and experimental pursuits. Here, compressing single-crystal coesite SiO₂ under hydrostatic pressures of 26-53 GPa at room temperature, we discover a new polymorphic phase transition mechanism of coesite to post-stishovite, by means of single-crystal synchrotron X-ray diffraction experiment and first-principles computational modelling. The transition features the formation of multiple previously unknown triclinic phases of SiO₂ on the transition pathway as structural intermediates. Coexistence of the low-symmetry phases results in extensive splitting of the original coesite X-ray diffraction peaks that appear as dramatic peak broadening and weakening, resembling an amorphous material. This work sheds light on the long-debated pressure-induced amorphization phenomenon of SiO₂, but also provides new insights into the densification mechanism of tetrahedrally bonded structures common in nature.