By　means　of　density　functional　theory　in　conjunction　with　a　periodic　slab　model,　we　have　investigated　the　interaction　Of　Cl-2　molecule　with　Ag　atoms　supported　on　the　perfect　and　defect　MgO(0　0　1)　surfaces.　The　results　indicate　that　Ag　atoms　supported　on　the　MgO(0　0　1)　surface,　especially　on　the　defect　MgO(0　0　1)　surface　with　oxygen　vacancies,　exhibit　high　reactivity　towards　the　adsorption　and　dissociation　of　molecular　Cl-2.　The　minimum　energy　path　discloses　that　the　dissociation　process　Of　Cl-2　on　Ag/MgO(0　0　1)　has　no　energy　barrier.　Band　structure　and　charge　density　analysis　further　illustrates　that　the　MgO(0　0　1)　surface　not　only　serves　as　the　support　of　Ag　atom　but　also　participate　in　the　interaction　with　Cl-2　molecule;　and　the　obvious　charge　transfer　from　the　surface　to　the　adsorbate　is　observed.　(c)　2006　Elsevier　B.V.　All　rights　reserved.