Identification of post-pyrite phase transitions in SiO2 by a genetic algorithm
| Title | Identification of post-pyrite phase transitions in SiO2 by a genetic algorithm |
| Publication Type | Journal Article |
| Year of Publication | 2011 |
| Authors | Wu SQ, Umemoto K, Ji M, Wang CZ, Ho KM, Wentzcovitch RM |
| Journal Title | Physical Review B |
| Volume | 83 |
| Pages | 184102 |
| Date Published | 05/16 |
| ISBN Number | 1098-0121 |
| Accession Number | ISI:000290709300002 |
| Keywords | crystal-structure, gas, lower mantle, mgsio3, molecular-dynamics, namgf3, perovskite phase, planets, principles |
| Abstract | 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 Fe2P--> 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 Fe2P 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. |
| URL | <Go to ISI>://000290709300002 |
| DOI | 10.1103/PhysRevB.83.184102 |
| Alternate Journal | Phys Rev BPhys Rev B |
