title: Polymorphic phase transition mechanism of compressed coesite.
abstract: 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.
authors: 1] Center for High Pressure Science and Technology Advanced Research, Shanghai 201203, China [2] School of Physics, Astronomy and Computational Sciences, George Mason University, Fairfax, Virginia 22030, USA [3] Geophysical Laboratory, Carnegie Institution of Washington, Washington, District Of Columbia 20015, USA.
authors: Q Y
authors: QY
authors: Hu
authors: Geophysical Laboratory, Carnegie Institution of Washington, Washington, District Of Columbia 20015, USA.
authors: J-F
authors: JF
authors: Shu
authors: School of Physics, Astronomy and Computational Sciences, George Mason University, Fairfax, Virginia 22030, USA.
authors: A
authors: A
authors: Cadien
authors: 1] Geophysical Laboratory, Carnegie Institution of Washington, Washington, District Of Columbia 20015, USA [2] High Pressure Collaborative Access Team, Geophysical Laboratory, Carnegie Institution of Washington, Argonne, Illinois 60439, USA.
authors: Y
authors: Y
authors: Meng
authors: 1] Center for High Pressure Science and Technology Advanced Research, Shanghai 201203, China [2] Geophysical Laboratory, Carnegie Institution of Washington, Washington, District Of Columbia 20015, USA.
authors: W G
authors: WG
authors: Yang
authors: 1] Center for High Pressure Science and Technology Advanced Research, Shanghai 201203, China [2] School of Physics, Astronomy and Computational Sciences, George Mason University, Fairfax, Virginia 22030, USA.
authors: H W
authors: HW
authors: Sheng
authors: 1] Center for High Pressure Science and Technology Advanced Research, Shanghai 201203, China [2] Geophysical Laboratory, Carnegie Institution of Washington, Washington, District Of Columbia 20015, USA.
authors: H-K
authors: HK
authors: Mao