The reactivity of yttrium atoms toward ammonia is revisited using expanded density functional theory calculations. The new results reveal that absorption of NH3 on YNH is dissociative to form Y(NH2)(2). The di-amide species can adsorb further NH3 Molecules molecularly to form Y(NH2)(2)NH3 and Y(NH2)(2)(NH3)(2). The calculations aimed to reveal the detail of the potential energy curves between the imide and the di-arnide forms. The Y(NH2)(2)(NH3)(x) species are more stable than those of YNH(NH3)(x) by more than 20 kcal/mol.