Gobrecht, D, Bromley, ST, Plane, JMC orcid.org/0000-0003-3648-6893 et al. (2 more authors) (2019) On the onset of dust formation in AGB stars. In: Proceedings of the International Astronomical Union. IAUS 343: Why Galaxies Care About AGB Stars: A Continuing Challenge through Cosmic Time, 20-23 Aug 2018, Vienna, Austria. Cambridge University Press (CUP) , pp. 119-128.
Abstract
A promising candidate to initiate dust formation in oxygen-rich AGB stars is alumina (Al2O3) showing an emission feature around ∼13μm attributed to Al−O stretching and bending modes (Posch+99,Sloan+03). The counterpart to alumina in carbon-rich AGB atmospheres is the highly refractory silicon carbide (SiC) showing a characteristic feature around 11.3μm (Treffers74). Alumina and SiC grains are thought to represent the first condensates to emerge in AGB stellar atmospheres. We follow a bottom-up approach, starting with the smallest stoichiometric clusters (i.e. Al4O6, Si2C2), successively building up larger-sized clusters. We present new results of quantum-mechanical structure calculations of (Al2O3)n, n = 1−10 and (SiC)n clusters with n = 1−16, including potential energies, rotational constants, and structure-specific vibrational spectra. We demonstrate the energetic viability of homogeneous nucleation scenarios where monomers (Al2O3 and SiC) or dimers (Al4O6 and Si2C2) are successively added. We find significant differences between our quantum theory based results and nanoparticle properties derived from (classical) nucleation theory.
Metadata
Item Type: | Proceedings Paper |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © International Astronomical Union 2019. This article has been published in a revised form in Proceedings of the International Astronomical Union https://doi.org/10.1017/S1743921318006014. This version is free to view and download for private research and study only. Not for re-distribution, re-sale or use in derivative works. " |
Keywords: | dust formation; molecular clusters; nucleation; alumina; silicon carbid; global optimisation; bottom-up; chemical-kinetics |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Engineering & Physical Sciences (Leeds) > School of Chemistry (Leeds) > Physical Chemistry (Leeds) |
Depositing User: | Symplectic Publications |
Date Deposited: | 24 Feb 2020 16:49 |
Last Modified: | 30 Jun 2020 00:38 |
Status: | Published |
Publisher: | Cambridge University Press (CUP) |
Identification Number: | 10.1017/s1743921318006014 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:156852 |