Journal
AMERICAN MINERALOGIST
Volume 107, Issue 11, Pages 2034-2043Publisher
MINERALOGICAL SOC AMER
DOI: 10.2138/am-2022-8420
Keywords
Grain boundary; complexion; forsterite; molecular dynamic; ab initio
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Funding
- French government through the Programme Investissement d'Avenir [I-SITE ULNE/ANR-16-IDEX-0004 ULNE]
- European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program [787198-TimeMan]
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In this work, we investigated the low-energy complexions of the symmetrical tilt grain boundary in forsterite. Through molecular dynamics and first principles calculations, we found six stoichiometric complexions and studied the segregation of MgO vacancy pairs. The vacancies were found to preferentially lie within the grain boundaries and lead to non-stoichiometric structures. Additionally, we observed the presence of free oxygen ions in many grain boundary complexions, which could have significant implications for geological processes.
In this work we explore the low-energy complexions of the symmetrical tilt grain boundary (GB) 60.8 degrees//[100](011) in forsterite through molecular dynamics and first principles calculations. Using a conservative sampling, we find six stoichiometric complexions with energies ranging from 0.66 to 1.25 J/m(2). We investigate the segregation of MgO vacancy pairs, and find that in most cases it is more favorable for the vacancies to lie within the GBs than in the surrounding crystals, leading to new atomic structures. From these results we infer that at finite temperature when vacancies are present in the system, GBs are likely to absorb them and to be non-stoichiometric. We find many GB complexions containing a free oxygen ion, which may have profound implications for geological processes.
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