J/A+A/690/A34ivo://CDS.VizieR/J/A+A/690/A34doi:10.26093/cds/vizier.36900034CDSLecoq-Molinos H.Gobrecht D.Sindel J.P.Helling C.Decin L.2025-02-18T20:01:25Z2024-09-26T11:39:40ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.fratomic-physicsAs a refractory material vanadia (solid V2O5) is likely to be found as a condensate in the atmospheres of substellar objects such as exoplanets and brown dwarfs. However, the nature of the nanometer-sized vanadium oxide clusters that partake in the nucleation process is not well understood. 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 and to investigate how they contribute to the formation of condensation seeds. We applied a hierarchical optimization approach in order to find the most favorable structures for clusters of (VO)N and (VO2)N for N=1-10, and of (V2O5)N for N=1-4 and to calculate their thermodynamical potentials. The candidate geometries are initially optimized by applying classical interatomic potentials; these are then refined at the B3LYP/cc-pVTZ level of theory to obtain accurate zeropoint energies and thermochemical quantities. We present previously unreported vanadium oxide cluster structures as the lowest-energy isomers. Moreover, 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 ~1000K, while molecular VO is the most abundant between ~1000K and ~2000K. We determine the nucleation rates of each stoichiometric family for a given (Tgas, pgas) profile of a brown dwarf using both 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 ~1000K. These abundance changes subsequently have 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.2024A&A...690A..34Lhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/690/A34CatalogResearchIsServedByTAP VizieR generic servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/690/A34https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/690/A34http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/690/A34https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/690/A34https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/690/A34http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/690/A34GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapdefaultJ/A+A/690/A34/vo_cCoordinates of the global minima candidate for VON molecular clustersrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintClustermolecular cluster typemeta.codecharTabTable identifier, NN_Nmeta.id;meta.tablecharAtomAtomic symbol of the atomphys.atmol.elementcharxx coordinate of the atom [Angstrom]0.1nmpos.cartesian.xdoubleyy coordinate of the atom [Angstrom]0.1nmpos.cartesian.ydoublezz coordinate of the atom [Angstrom]0.1nmpos.cartesian.zdoubleJ/A+A/690/A34/vo_tThermochemical data for the global minima candidate for VON molecular clustersrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintClustermolecular cluster typemeta.codecharTabTable identifier, NN_Nmeta.id;meta.tablecharTTemperatureKphys.temperaturefloatSEntropy SJ.mol**-1.K**-1phys.atmoldoubleH-HoEnthalpy difference to reference temperature (298.15)kJ/molmeta.ref;phys.temperature;arith.diffdoubleDELTAfHEnthalpy of formationkJ/molphys.SFRDELTAfGGibbs free energy of formationkJ/molphys.SFRJ/A+A/690/A34/vo2_cCoordinates of the global minima candidate for VO2N molecular clustersrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintClustermolecular cluster typemeta.codecharTabTable identifier, NN_Nmeta.id;meta.tablecharAtomAtomic symbol of the atomphys.atmol.elementcharxx coordinate of the atom [Angstrom]0.1nmpos.cartesian.xdoubleyy coordinate of the atom [Angstrom]0.1nmpos.cartesian.ydoublezz coordinate of the atom [Angstrom]0.1nmpos.cartesian.zdoubleJ/A+A/690/A34/vo2_tThermochemical data for the global minima candidate for VO2N molecular clustersClustermolecular cluster typemeta.codecharDELTAfHEnthalpy of formationkJ/molphys.SFRDELTAfGGibbs free energy of formationkJ/molphys.SFRrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintTabTable identifier, NN_Nmeta.id;meta.tablecharTTemperatureKphys.temperaturefloatSEntropy SJ.mol**-1.K**-1phys.atmoldoubleH-HoEnthalpy difference to reference temperature (298.15)kJ/molmeta.ref;phys.temperature;arith.diffdoubleJ/A+A/690/A34/v2o5_cCoordinates of the global minima candidate for V2O5N molecular clustersrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintClustermolecular cluster typemeta.codecharTabTable identifier, NN_Nmeta.id;meta.tablecharAtomAtomic symbol of the atomphys.atmol.elementcharxx coordinate of the atom [Angstrom]0.1nmpos.cartesian.xdoubleyy coordinate of the atom [Angstrom]0.1nmpos.cartesian.ydoublezz coordinate of the atom [Angstrom]0.1nmpos.cartesian.zdoubleJ/A+A/690/A34/v2o5_tThermochemical data for the global minima candidate for V2O5N molecular clustersDELTAfHEnthalpy of formationkJ/molphys.SFRDELTAfGGibbs free energy of formationkJ/molphys.SFRrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintTabTable identifier, NN_Nmeta.id;meta.tablecharTTemperatureKphys.temperaturefloatSEntropy SJ.mol**-1.K**-1phys.atmoldoubleH-HoEnthalpy difference to reference temperature (298.15)kJ/molmeta.ref;phys.temperature;arith.diffdoubleClustermolecular cluster typemeta.codechar