Vanadium oxide clusters in substellar atmospheres: A quantum chemical study

Abstract

We aim to understand the formation of cloud condensation nuclei in oxygen-rich substellar atmospheres by calculating fundamental properties of the energetically most favorable vanadium oxide molecules and clusters. A hierarchical optimization approach is applied in order to find the most favorable structures for clusters of (VO)${}_N$ and (VO${}_2$)${}_N$ for N=1-10, and (V${}_2$O${}_5$)${}_N$ for N=1-4 and to calculate their thermodynamical potentials. The candidate geometries are initially optimized applying classical interatomic potentials and then refined at the B3LYP/cc-pVTZ level of theory to obtain accurate zero-point energies and thermochemical quantities. We present previously unreported vanadium oxide cluster structures as lowest-energy isomers. We report revised cluster energies and their thermochemical properties. Chemical equilibrium calculations are used to asses the impact of the updated and newly derived thermodynamic potentials on the gas-phase abundances of vanadium-bearing species. In chemical equilibrium, larger clusters from different stoichiometric families are found to be the most abundant vanadium-bearing species for temperatures below ~1000 K, while molecular VO is the most abundant between ~1000 K and ~2000 K. We determine the nucleation rates of each stoichiometric family for a given (T${}_{gas}$, p${}_{gas}$) profile of a brown dwarf using classical and non-classical nucleation theory. Small differences in the revised Gibbs free energies of the clusters have a large impact on the abundances of vanadium bearing species in chemical equilibrium at temperatures below ~1000 K, which subsequently has an impact on the nucleation rates of each stoichiometric family. We find that with the revised and more accurate cluster data non-classical nucleation rates are up to 15 orders of magnitude higher than classical nucleation rates.

arXiv commentaccepted to A&A, 16 pages, 10 figures

References in corpus (34)

• The chemical composition of the Sun
• Detection of an Extrasolar Planet Atmosphere
• Clouds in the atmosphere of the super-Earth exoplanet GJ 1214b
• Precipitating Condensation Clouds in Substellar Atmospheres
• From thermal dissociation to condensation in the atmospheres of ultra hot Jupiters: WASP-121b in context
• Equilibrium chemistry down to 100 K - Impact of silicates and phyllosilicates on carbon/oxygen ratio
• Early Release Science of the exoplanet WASP-39b with JWST NIRISS
• Detection of H2O and evidence for TiO/VO in an ultra hot exoplanet atmosphere
• Dust formation in the oxygen-rich AGB star IK Tau
• Dust in Brown Dwarfs and Extra-solar Planets I. Chemical composition and spectral appearance of quasi-static cloud layers
• Hot Exoplanet Atmospheres Resolved with Transit Spectroscopy (HEARTS) IV. A spectral inventory of atoms and molecules in the high-resolution transmission spectrum of WASP-121 b
• Dust in brown dwarfs and extra-solar planets II. Cloud formation for cosmologically evolving abundances
• Aerosols in Exoplanet Atmospheres
• A HST/WFC3 Thermal Emission Spectrum of the Hot Jupiter HAT-P-7b
• Exoplanet Clouds
• Vanadium oxide and a sharp onset of cold-trapping on a giant exoplanet
• Study of the inner dust envelope and stellar photosphere of the AGB star R Doradus using SPHERE/ZIMPOL
• An emission spectrum for WASP-121b measured across the 0.8-1.1 micron wavelength range using the Hubble Space Telescope
• Non-detection of TiO and VO in the atmosphere of WASP-121b using high-resolution spectroscopy
• Tracing the phase transition of Al-bearing species from molecules to dust in AGB winds. Constraining the presence of gas-phase (Al2O3)n clusters
• Seed particle formation for silicate dust condensation by SiO nucleation
• A Tale of Planet Formation: From Dust to Planets
• Confirmation of water emission in the dayside spectrum of the ultrahot Jupiter WASP-121b
• Cloud property trends in hot and ultra-hot giant gas planets (WASP-43b, WASP-103b, WASP-121b, HAT-P-7b, and WASP-18b)
• Bottom-up dust nucleation theory in oxygen-rich evolved stars I. Aluminium oxide clusters
• Nucleation of small silicon carbide dust clusters in AGB stars
• Developing a self-consistent AGB wind model: II. Non-classical, non-equilibrium polymer nucleation in a chemical mixture
• Exoplanet weather and climate regimes with clouds and thermal ionospheres: A model grid study in support of large-scale observational campaigns
• Ultracool Dwarfs Observed with the Spitzer Infrared Spectrograph -- III. Dust Grains in Young L Dwarf Atmospheres Are Heavier
• Clouds form on the hot Saturn JWST ERO target WASP-96b
• Hydrocarbon chemistry in inner regions of planet forming disks
• A global optimisation study of the low-lying isomers of the alumina octomer (Al${}_2$O${}_3$)${}_8$
• Revisiting fundamental properties of TiO${}_2$ nanoclusters as condensation seeds in astrophysical environments
• Detection of TiO and VO in the atmosphere of WASP-121b and Evidence for its temporal variation

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