Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
5787301 | Physics of the Earth and Planetary Interiors | 2017 | 7 Pages |
Abstract
Phase-Pi (Al3Si2O7(OH)3) is an aluminosilicate hydrous mineral and is likely to be stable in hydrated sedimentary layers of subducting slabs. Phase-Pi is likely to be stable between the depths of 60 and 200Â km and is likely to transport water into the Earth's interior. Here, we use first principles simulations based on density functional theory to explore the crystal structure at high-pressure, equation of state, and full elastic stiffness tensor as a function of pressure. We find that the pressure volume results could be described by a finite strain fit with V0, K0, and K0â² being 310.3Â Ã
3, 133Â GPa, and 3.6 respectively. At zero pressure, the full elastic stiffness tensor shows significant anisotropy with the diagonal principal components C11, C22, and C33 being 235, 292, 266Â GPa respectively, the diagonal shear C44, C55, and C66 being 86, 92, and 87Â GPa respectively, and the off-diagonal stiffness C12, C13, C14,C15, C16, C23, C24, C25, C26, C34, C35, C36, C45, C46, and C56 being 73, 78, 6, â30, 15, 61, 17, 2, 1, â13, â15, 6, 3, 1, and 3Â GPa respectively. The zero pressure, shear modulus, G0 and its pressure derivative, G0â² are 90Â GPa and 1.9 respectively. Upon compression, hydrogen bonding in phase-Pi shows distinct behavior, with some hydrogen bonds weakening and others strengthening. The latter eventually undergo symmetrization, at pressure greater (>40Â GPa) than the thermodynamic stability of phase-Pi. Full elastic constant tensors indicate that phase-Pi is very anisotropic with AVP â¼22.4% and AVS â¼23.7% at 0Â GPa. Our results also indicate that the bulk sound velocity of phase-Pi is slower than that of the high-pressure hydrous aluminosilicate phase, topaz-OH.
Related Topics
Physical Sciences and Engineering
Earth and Planetary Sciences
Geophysics
Authors
Ye Peng, Mainak Mookherjee, Andreas Hermann, Suraj Bajgain, Songlin Liu, Bernd Wunder,