title: The pyrite-type high-pressure form of silica.
abstract: Silica (SiO2) exhibits extensive polymorphism at elevated pressures. X-ray diffraction measurements showed that a high-pressure form with a pyrite-type structure, denser than other known silica phases, is stable above 268 giga-pascals and 1800 kelvin. The silicon coordination number increases from 6 in the alpha-PbO2-type phase to 6+2 in the pyrite-type phase, leading to a large increase in density by about 5% at the phase transition.
authors.affiliation: Department of Earth and Planetary Sciences, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro, Tokyo 152-8551, Japan. ykuwayam@geo.titech.ac.jp
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Kuwayama
authors.forename: Kei
authors.initials: K
authors.lastname: Hirose
authors.forename: Nagayoshi
authors.initials: N
authors.lastname: Sata
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Ohishi