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Title: Local structure of molten AuGa 2 under pressure: Evidence for coordination change and planetary implications

Abstract

In situ x-ray diffraction measurements and inverse Monte Carlo simulations of pair distribution functions were used to characterize the local structure of molten AuGa 2 up to 16 GPa and 940 K. Our results document systematic changes in liquid structure due to a combination of bond compression and coordination increase. Empirical potential structure refinement shows the first-neighbor coordination of Ga around Au and of Au around Ga to increase from about 8 to 10 and 4 to 5, respectively between 0 and 16 GPa, and the inferred changes in liquid structure can explain the observed melting-point depression of AuGa2 up to 5 GPa. As intermetallic AuGa 2 is an analogue for metallic SiO 2 at much higher pressures, our results imply that structural changes documented for non-metallic silicate melts below 100 GPa are followed by additional coordination changes in the metallic state at pressures in the 0.2–1 TPa range achieved inside large planets.

Authors:
 [1];  [2];  [3];  [2]
  1. Hacettepe Univ, Ankara (Turkey); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  2. Univ. of California, Berkeley, CA (United States)
  3. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Publication Date:
Research Org.:
Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA); USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1436513
Alternate Identifier(s):
OSTI ID: 1462006
Grant/Contract Number:  
NA0002198; AC02-05CH11231
Resource Type:
Accepted Manuscript
Journal Name:
Scientific Reports
Additional Journal Information:
Journal Volume: 8; Journal Issue: 1; Journal ID: ISSN 2045-2322
Publisher:
Nature Publishing Group
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 79 ASTRONOMY AND ASTROPHYSICS; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY

Citation Formats

Kalkan, Bora, Godwal, Budhiram, Raju, Selva Vennila, and Jeanloz, Raymond. Local structure of molten AuGa2 under pressure: Evidence for coordination change and planetary implications. United States: N. p., 2018. Web. doi:10.1038/s41598-018-25297-9.
Kalkan, Bora, Godwal, Budhiram, Raju, Selva Vennila, & Jeanloz, Raymond. Local structure of molten AuGa2 under pressure: Evidence for coordination change and planetary implications. United States. doi:10.1038/s41598-018-25297-9.
Kalkan, Bora, Godwal, Budhiram, Raju, Selva Vennila, and Jeanloz, Raymond. Tue . "Local structure of molten AuGa2 under pressure: Evidence for coordination change and planetary implications". United States. doi:10.1038/s41598-018-25297-9. https://www.osti.gov/servlets/purl/1436513.
@article{osti_1436513,
title = {Local structure of molten AuGa2 under pressure: Evidence for coordination change and planetary implications},
author = {Kalkan, Bora and Godwal, Budhiram and Raju, Selva Vennila and Jeanloz, Raymond},
abstractNote = {In situ x-ray diffraction measurements and inverse Monte Carlo simulations of pair distribution functions were used to characterize the local structure of molten AuGa2 up to 16 GPa and 940 K. Our results document systematic changes in liquid structure due to a combination of bond compression and coordination increase. Empirical potential structure refinement shows the first-neighbor coordination of Ga around Au and of Au around Ga to increase from about 8 to 10 and 4 to 5, respectively between 0 and 16 GPa, and the inferred changes in liquid structure can explain the observed melting-point depression of AuGa2 up to 5 GPa. As intermetallic AuGa2 is an analogue for metallic SiO2 at much higher pressures, our results imply that structural changes documented for non-metallic silicate melts below 100 GPa are followed by additional coordination changes in the metallic state at pressures in the 0.2–1 TPa range achieved inside large planets.},
doi = {10.1038/s41598-018-25297-9},
journal = {Scientific Reports},
number = 1,
volume = 8,
place = {United States},
year = {2018},
month = {5}
}

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Cited by: 1 work
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Figures / Tables:

Table 1 Table 1: Pressures measured during heating for individual experimental runs, with C, O and M representing cubic (fluorite), orthorhombic (cotunnite) and monoclinic (“post-cotunnite”) phases. Uncertainties in pressure and temperature are up to ±2 GPa and ±5 K.

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