English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Unravelling the composition and characteristics of gas and dust lost byasymptotic giant branch (AGB) stars is important as these stars play a vitalrole in the chemical life cycle of galaxies. The general hypothesis of theirmass loss mechanism is a combination of stellar pulsations and radiativepressure on dust grains. However, current models simplify dust formation, whichstarts as a microscopic phase transition called nucleation. Various nucleationtheories exist, yet all assume chemical equilibrium, growth restricted bymonomers, and commonly use macroscopic properties for a microscopic process.Such simplifications for initial dust formation can have large repercussions onthe type, amount, and formation time of dust. By abandoning equilibriumassumptions, discarding growth restrictions, and using quantum mechanicalproperties, we have constructed and investigated an improved nucleation theoryin AGB wind conditions for four dust candidates, TiO$_2$, MgO, SiO andAl$_2$O$_3$. This paper reports the viability of these candidates as first dustprecursors and reveals implications of simplified nucleation theories. Monomerrestricted growth underpredicts large clusters at low temperatures andoverpredicts formation times. Assuming the candidates are present, Al$_2$O$_3$is the favoured precursor due to its rapid growth at the highest consideredtemperatures. However, when considering an initially atomic chemical mixture,only TiO$_2$-clusters form. Still, we believe Al$_2$O$_3$ to be the primecandidate due to substantial physical evidence in presolar grains, observationsof dust around AGB stars at high temperatures, and its ability to form at hightemperatures and expect the missing link to be insufficient quantitative dataof Al-reactions.

Developing a self-consistent AGB wind model: II. Non-classical, non-equilibrium polymer nucleation in a chemical mixture