Abstract EANA2024-93

Observations of numerous gaseous exoplanets have revealed the presence of clouds in their atmospheres. These clouds form from a complex set of physical and chemical processes which are not fully understood. In this work, we study the first steps of cloud formation, nucleation, in gaseous atmospheres using quantum chemistry calculations of metal oxide clusters, including vanadium oxide, titanium oxide and silicon oxide.
Nucleation occurs when gas-phase molecules cluster together to form nanometer-sized particles (i. e. nanoclusters), which can further coagulate into macroscopic dust grains that provide a surface for the cloud materials to condense on. The process is highly dependent on the characteristics of the clusters such as their potential energies, geometries and spectral properties, all of which are not well known. We apply a bottom-up approach to obtain the geometries and thermochemical energies of global minima candidate structures for the different metal oxides. Each structure has been calculated by applying Density Functional Theory at the B3LYP/cc-pVTZ level of theory.
We present thermochemical results for VO, V2O5, TiO and SiO that are in accordance with the experimental energies listed in the JANAF-NIST tables. Further, we provide updated values for VO2, as well as results for larger structures that are not currently available in the literature. We use a chemical equilibrium code to explore astrophysical environments for which each metal oxide nucleation will be important, with a focus on exoplanet atmospheres. With our revised cluster data, we calculate non-classical nucleation rates which are up to 15 orders of magnitude higher than classical nucleation rates. We compute the vibrational spectra and absorption cross sections of all clusters and found that the strongest emission peaks lie within the JWST-MIRI wavelength range.