The PES, in turn, is defined by the chemical composition, total number of electrons, spin multiplicity, and the DFT methods (level of theory and other calculation parameters) employed. In this definition, every unique atomic structure (in terms of interatomic distances and angles) corresponding to a local PES minimum obtained via a geometry optimization calculation is a different molecule. It is worth noting that this PES-based definition is used within the Materials Project's data for crystalline solids to define a unique "material".