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Title: Elasticity and phase transformation at high pressure in coesite from experiments and first-principles calculations

Here, the crystal structure and equation of state of coesite (space group C2/ c) and its high pressure polymorph coesite-II (space group P2 1/ n) under pressure have been studied using X-ray powder diffraction in a diamond anvil cell (DAC) up to 31 GPa at room temperature and first-principles calculations at 0 K up to 45 GPa. New diffraction peaks appear above 20 GPa, indicating the formation of coesite-II structure. The calculated enthalpies provide theoretical support for the pressure-induced phase transformation from coesite to coesite-II at ~21.4 GPa. Compared with coesite, the coesite-II structure is characterized by a ‘doubled’ b-axis and the breakdown of the linear Si1-O1-Si1 angle in coesite into two distinct angles - one is ~176°, close to linear, whereas the other decreases by 22° to 158°. Coesite is very anisotropic with the a-axis the shortest and twice more compressible than the b- and c-axis. By comparison, coesite-II is not so anisotropic with similar compressibilities in its a-, b-, and c-axis. As analyzed by a third-order Eulerian finite strain equation of state, the bulk modulus of coesite at 21.4 GPa is 182.3GPa, and that of coesite-II is 140.8 GPa, indicating that coesite-II is much more compressible than coesite.more » Furthermore, the existence of coesite-II in the coldest subduction zone will change the elasticity and anisotropic properties of the subducting materials dramatically.« less
Authors:
 [1] ;  [1] ;  [1] ;  [2] ;  [2] ;  [1]
  1. Stony Brook Univ., Stony Brook, NY (United States)
  2. Univ. of Chinese Academy of Sciences, Beijing (China)
Publication Date:
Grant/Contract Number:
NA0001815
Type:
Accepted Manuscript
Journal Name:
American Mineralogist
Additional Journal Information:
Journal Volume: 101; Journal Issue: 5; Journal ID: ISSN 0003-004X
Publisher:
Mineralogical Society of America
Research Org:
Stony Brook Univ., Stony Brook, NY (United States)
Sponsoring Org:
USDOE National Nuclear Security Administration (NNSA)
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; 36 MATERIALS SCIENCE; coesite; phase transition; diamond anvil cell; first-principles calculation
OSTI Identifier:
1466808

Chen, Ting, Wang, Xuebing, Qi, Xintong, Ma, Maining, Xu, Zhishuang, and Li, Baosheng. Elasticity and phase transformation at high pressure in coesite from experiments and first-principles calculations. United States: N. p., Web. doi:10.2138/am-2016-5533.
Chen, Ting, Wang, Xuebing, Qi, Xintong, Ma, Maining, Xu, Zhishuang, & Li, Baosheng. Elasticity and phase transformation at high pressure in coesite from experiments and first-principles calculations. United States. doi:10.2138/am-2016-5533.
Chen, Ting, Wang, Xuebing, Qi, Xintong, Ma, Maining, Xu, Zhishuang, and Li, Baosheng. 2016. "Elasticity and phase transformation at high pressure in coesite from experiments and first-principles calculations". United States. doi:10.2138/am-2016-5533. https://www.osti.gov/servlets/purl/1466808.
@article{osti_1466808,
title = {Elasticity and phase transformation at high pressure in coesite from experiments and first-principles calculations},
author = {Chen, Ting and Wang, Xuebing and Qi, Xintong and Ma, Maining and Xu, Zhishuang and Li, Baosheng},
abstractNote = {Here, the crystal structure and equation of state of coesite (space group C2/c) and its high pressure polymorph coesite-II (space group P21/n) under pressure have been studied using X-ray powder diffraction in a diamond anvil cell (DAC) up to 31 GPa at room temperature and first-principles calculations at 0 K up to 45 GPa. New diffraction peaks appear above 20 GPa, indicating the formation of coesite-II structure. The calculated enthalpies provide theoretical support for the pressure-induced phase transformation from coesite to coesite-II at ~21.4 GPa. Compared with coesite, the coesite-II structure is characterized by a ‘doubled’ b-axis and the breakdown of the linear Si1-O1-Si1 angle in coesite into two distinct angles - one is ~176°, close to linear, whereas the other decreases by 22° to 158°. Coesite is very anisotropic with the a-axis the shortest and twice more compressible than the b- and c-axis. By comparison, coesite-II is not so anisotropic with similar compressibilities in its a-, b-, and c-axis. As analyzed by a third-order Eulerian finite strain equation of state, the bulk modulus of coesite at 21.4 GPa is 182.3GPa, and that of coesite-II is 140.8 GPa, indicating that coesite-II is much more compressible than coesite. Furthermore, the existence of coesite-II in the coldest subduction zone will change the elasticity and anisotropic properties of the subducting materials dramatically.},
doi = {10.2138/am-2016-5533},
journal = {American Mineralogist},
number = 5,
volume = 101,
place = {United States},
year = {2016},
month = {5}
}