Chemical modelling substantially contributes to recent development of current technology and science. Major contributions were made in e.g. catalyst development, to tailor polymerization, or to optimize fuels and their combustion, and in the field of atmospheric chemistry. These models consist of thermodynamic and kinetic data and potentially further properties like transport data etc. Acquiring data for these models is possible via experiments or, nowadays to an increasing extent, from ab initio calculations, i.e. quantum chemistry. Quantum chemistry methods are usually made up of two ingredients according to the ubiquitous Born-Oppenheimer (BO) approximation: on the one hand, there are electronic potential energies, which can nowadays be computed at high accuracy; on the other hand, there are models for nuclear motion that often suffer from shortcomings of the widespread rigid rotor harmonic oscillator (RRHO) model. While electronic potential energies largely influence enthalpies, models for nuclear motion mostly affect the entropy predictions and henceforth free energies, reaction kinetics and equilibria.