Ab initio investigation of the high pressure elasticity of Mg2SiO4 forsterite and ringwoodite

Lars Stixrude, R. M. Wentzcovitch, C. Da Silva, B. Kiefer

Research output: Contribution to journalConference articlepeer-review

2 Scopus citations

Abstract

We discuss the behavior of two minerals of the same composition, Mg2SiO4 but different structures: forsterite and ringwoodite. Ab initio plane-wave pseudopotential results are discussed in terms of the full elastic constant tensors of these phases and their elastic anisotropy. The structures of the two minerals, based on pseudo-hcp and pseudo-fcc packing of oxygens, respectively, show very different behavior at high pressure. While the elastic anisotropy of olivine depends weakly on pressure between 0 and 25 GPa, the anisotropy of ringwoodite decreases with pressure initially, vanishing at 17 GPa before increasing again at higher pressure. This unusual behavior is understood in terms of a change of sign of the combination of elastic constants c12+2c44-c11, and a resulting interchange of fast and slow directions of acoustic wave propagation. To gain insight into the origin of their elastic behavior, the ab initio results are compared with a simple model based on the O sub-lattice.

Original languageEnglish (US)
Pages (from-to)15-25
Number of pages11
JournalMaterials Research Society Symposium - Proceedings
Volume499
StatePublished - Dec 1 1998
EventProceedings of the 1997 MRS Fall Symposium - Boston, MA, USA
Duration: Dec 2 1997Dec 4 1997

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