The chemical composition of stars: high-precision spectroscopy with three-dimensional model stellar atmospheres

The determination of stellar chemical compositions is pivotal for our understanding of the formation and evolution of stars, planetary systems, and galaxies. In order to derive elemental abundances in stars, it is necessary to interpret observational data with the aid of models of stellar atmospheres and of spectral line formation processes. I propose to apply realistic, state-of-the-art, three-dimensional (3D), hydrodynamic, model stellar atmospheres to the analysis of stellar spectra. I will develop 3D simulations of the outer layers of stars and investigate the effects of non-equilibrium chemistry and non-equilibrium ionization and excitation of atoms in stellar atmospheres, which are largely neglected by current spectroscopic analyses.