Structure and reactivity of carbon multivacancies in graphene

► In this study, we characterize the structure and the reactivity of multivacancies created in a graphene sheet. ► The stability of multivacancies is due to the formation of pentagons on their edges. ► Vacancies with an even number of missing atoms are more stable than vacancies with odd number of missing atoms. ► Less stable vacancies are also the most reactive with respect to oxygen and water adsorption. ► The final product of the reaction depends on the vacancy size.