TiO2 nanoclusters fundamental properties

We employed a hierarchical optimisation approach, consisting of a force-field description, density-functional based tight-binding, and all-electron density-functional theory (DFT) to obtain accurate zero-point energies and thermochemical properties for the clusters. In 129 combinations of functionals and basis sets, we find that B3LYP/cc-pVTZ, including Grimme's empirical dispersion, performs most accurately with respect to experimentally derived thermochemical properties of the TiO_2_ molecule.

We present a hitherto unreported global minimum candidate for size N=13. The DFT-derived thermochemical cluster data are used to evaluate the nucleation rates for a given temperature-pressure profile of a model hot-Jupiter atmosphere. We find that with the updated and refined cluster data, nucleation becomes unfeasible at slightly lower temperatures, raising the lower boundary for seed formation in the atmosphere.

The approach presented in this paper allows finding stable isomers for small (TiO_2_)N clusters. The choice of the functional and basis set for the all-electron DFT calculations has a measurable impact on the resulting surface tension and nucleation rate, and the updated thermochemical data are recommended for future considerations.