The　adsorption　and　dissociation　of　two　NO　molecules　on　Cu2O(111)　surface　have　been　studied　with　the　periodic　slab　model　by　using　the　density　functional　theory　(DFT)　and　the　generalized　gradient　approximation　(GGA)　with　the　Perdew-　Burke-Ernzerhof　(PBE)　exchange-correlation　functional.　Three　kinds　of　structures,　Cu+(NO)(NO),　Cu+(NO)(ON),　and　Cu+(ON)(ON),　with　the　singlet　and　triplet　states　were　considered.　Their　corresponding　adsorption　energies　and　Mulliken　charges　were　calculated.　The　calculated　results　indicate　that　in　the　optimized　Cu+(ON)(ON)　configuration,　two　adsorbed　NO　molecules　form　a　dimeric　species　with　a　much　shorter　N{single　bond}N　bond　length　(about　124.4　pm).　Such　a　configuration　contributes　to　the　dissociation　of　NO,　leading　to　the　formation　of　Cu-O　surface　species　with　elimination　of　N2　or　N2O.　©　2006　Chinese　Chemical　Society　and　College　of　Chemistry　and　Molecular　Engineering,　Peking　University.