Astronomers use "metal" in an odd sense -- only implying the presence of metallic elements, but not necessarily in their elemental, i.e. metallic, form, which is how others use the term.
Most of the compounds used in the model described in the original pub'n would be rocks at normal temps.
The temperature of LTT 9779 b is high. In order to study the extreme cases, we decided to consider titanium-based condensates, which are the most refractory condensates that can form in hot exoplanets together with silicate clouds, which have often been considered in previous studies of hot Jupiters (Lecavelier des Etangs et al. 2003; Parmentier et al. 2016; Wakeford et al. 2017). Whereas silicate clouds have been used in previous studies with the ScCHIMERA code (Mai & Line 2019), we had to specifically include titanium-based condensates inside the code. Because the equilibrium condensation chemistry of titanium is complex, we decided to consider all the species as a single “titanium cloud” that are predicted to condense by the chemical equilibrium applications (CEA) code: Ti4O7, MgTi2O5, Ti3O5, Ti4O7, CaTiO3, Ti4O7, Ca4Ti3O10, Ca3Ti2O7, andTi2 O3. We then considered this titanium cloud to have the same optical properties as CaTiO3 clouds.
https://www.aanda.org/articles/aa/full_html/2023/07/aa46117-23/aa46117-23.htmlThe Ti=O bond is one of the strongest in the Universe; IR bands due to TiO show up in stars at higher temps than any other molecular absorption band.
TiO2 is familiar as "titanium white" pigment in paints, and yes it is *highly* reflective as a solid, but absorbs IR in the vapor phase.
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