Density-functional study of the compressed (2√3 × 2√3)R30°-CO overlayer on the ferromagnetic Co(0001) surface

► The (23×23)R30∘-CO/Co(0001) system is studied theoretically. ► In the stable structure we find molecules reside in the atop or quasi-bridge sites. ► Two another metastable structures CO are also obtained. ► The average magnetic moment per surface Co atom is about 1 μB.