title: Structural properties and phase transitions in a silica clathrate.
abstract: Melanophlogite, a low-pressure silica polymorph, has been extensively studied at different temperatures and pressures by molecular dynamics simulations. While the high-temperature form is confirmed as cubic, the low-temperature phase is found to be slightly distorted, in agreement with experiments. With increasing pressure, the crystalline character is gradually lost. At 8 GPa, the radial distribution function is consistent with an amorphous state. Like pristine glass, the topology changes, plastic behavior, and permanent densification appear above ∼12 GPa, triggered by Si coordination number changes. We predict that a partial crystalline and amorphous sample can be obtained by recovering the sample from a pressure of ∼12-16 GPa.
authors.affiliation: International School for Advanced Studies (SISSA), Trieste, Italy. y_liang@earth.kumst.kyoto-u.ac.jp
authors.forename: Yunfeng
authors.initials: Y
authors.lastname: Liang
authors.forename: Folorunso O
authors.initials: FO
authors.lastname: Ogundare
authors.forename: Caetano R
authors.initials: CR
authors.lastname: Miranda
authors.forename: Jamieson K
authors.initials: JK
authors.lastname: Christie
authors.forename: Sandro
authors.initials: S
authors.lastname: Scandolo