Density　functional　theory　has　been　employed　to　investigate　the　adsorption　and　the　dissociation　of　an　N　2　O　at　different　sites　on　perfect　and　defective　Cu　2　O(1　1　1)　surfaces.　The　calculations　are　performed　on　periodic　systems　using　slab　model.　The　Lewis　acid　site,　Cu　CUS　,　and　Lewis　base　site,　O　SUF　are　considered　for　adsorption.　Adsorption　energies　and　the　energies　of　the　dissociation　reaction　N　2　O　→　N　2　+　O(s)　at　different　sites　are　calculated.　The　calculations　show　that　adsorption　of　N　2　O　is　more　favorable　on　Cu　CUS　adsorption　site　energetically.　Cu　CUS　site　exhibits　a　very　high　activity.　The　Cu　CUS　-N　2　O　reaction　is　exothermic　with　a　reaction　energy　of　77.45　kJ　mol　-1　and　an　activation　energy　of　88.82　kJ　mol　-1　,　whereas　the　O　SUF　-N　2　O　reaction　is　endothermic　with　a　reaction　energy　of　205.21　kJ　mol　-1　and　an　activation　energy　of　256.19　kJ　mol　-1　.　The　calculations　for　defective　surface　indicate　that　O　vacancy　cannot　obviously　improve　the　catalytic　activity　of　Cu　2　O.　©　2007　Elsevier　B.V.　All　rights　reserved.