TY - JOUR
T1 - Identification of post-pyrite phase transitions in SiO2 by a genetic algorithm
AU - Wu, Shunqing
AU - Umemoto, Koichiro
AU - Ji, Min
AU - Wang, Cai Zhuang
AU - Ho, Kai Ming
AU - Wentzcovitch, Renata M
PY - 2011/5/16
Y1 - 2011/5/16
N2 - Using a first-principles genetic algorithm we predict an Fe2P phase is the first post-pyrite phase of SiO2 at low temperatures. This contrasts with a recently predicted cotunnite phase. Static enthalpy differences between these two phases are small near the transition pressure (0.69 TPa). While quasiharmonic free energy calculations predict an Fe 2P-→cotunnite-type transition with increasing temperature, another phase, NbCoB type, is identified as being structurally and energetically intermediate between Fe2P and cotunnite phases. This structure suggests a possible temperature-induced gradual transformation between Fe 2P and cotunnite phases. This finding would change our understanding of how planet-forming silicates, for example, MgSiO3 post-perovskite and its solid solutions, dissociate into elementary oxides at thermodynamic conditions expected in the interior of solar giants and exoplanets.
AB - Using a first-principles genetic algorithm we predict an Fe2P phase is the first post-pyrite phase of SiO2 at low temperatures. This contrasts with a recently predicted cotunnite phase. Static enthalpy differences between these two phases are small near the transition pressure (0.69 TPa). While quasiharmonic free energy calculations predict an Fe 2P-→cotunnite-type transition with increasing temperature, another phase, NbCoB type, is identified as being structurally and energetically intermediate between Fe2P and cotunnite phases. This structure suggests a possible temperature-induced gradual transformation between Fe 2P and cotunnite phases. This finding would change our understanding of how planet-forming silicates, for example, MgSiO3 post-perovskite and its solid solutions, dissociate into elementary oxides at thermodynamic conditions expected in the interior of solar giants and exoplanets.
UR - http://www.scopus.com/inward/record.url?scp=79961164008&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=79961164008&partnerID=8YFLogxK
U2 - 10.1103/PhysRevB.83.184102
DO - 10.1103/PhysRevB.83.184102
M3 - Article
AN - SCOPUS:79961164008
SN - 1098-0121
VL - 83
JO - Physical Review B - Condensed Matter and Materials Physics
JF - Physical Review B - Condensed Matter and Materials Physics
IS - 18
M1 - 184102
ER -