By using ab initio molecular dynamics calculations, we show that even where the graphene lattice
constant contracts, as previously reported for freestanding graphene below room temperature, the average
carbon-carbon distance increases with temperature, in both free and supported graphene. This results in a
larger corrugation at higher temperature, which can affect the interaction between graphene and the
supporting substrate. For a weakly interacting system as graphene/Ir(111), we confirm the results using an
experimental approach which gives direct access to interatomic distances.
