The　adsorption　of　N2　at　the　edge　of　a　single-wall　carbon　nanotube　(SWNT)　has　been　investigated　employing　an　ONIOM　approach.　It　was　found　that　N2　can　be　chemisorbed　at　the　edge　site　of　zigzag　SWNT　surface　and　the　N-N　bond　is　activated.　However,　the　adsorption　at　the　edge　site　of　armchair　SWNT　surface　is　rather　weak.　This　can　be　attributed　to　the　crucial　effect　of　local　edge　carbon　atoms　arrangement　of　the　defect　SWNT　surface　with　open　tips.　Furthermore,　our　results　strongly　reinforce　the　viewpoint　from　recent　experimental　observations　and　theoretical　studies　that　SWNTs　with　open　tips　exhibit　larger　adsorption　capacity　than　closed-ended　SWNTs.　©　2005　Elsevier　B.V.　All　rights　reserved.