NO chemisorption on a magnetic alloy surface: a density-functional periodic study of Pd3Mn(100) compared with Pd(100)

Self-consistent calculations based on density functional theory with gradie nt corrections are used to compare the adsorption of NO on Pd(100) and Pd3M n(100). There are two types of Pd3Mn(100) surfaces, one with only Pd atoms (A) and one with Pd and Mn atoms alternately ordered (B). For adsorption on surface A, the adsorption sites are in the same stability order as for pal ladium, with the atop site less stable than the bridge and the hollow ones, but all the binding energies are slightly weaker. For adsorption on surfac e B, the stability order is totally different, the atop Mn site being the m ost stable one. Therefore, NO prefers to adsorb on a magnetic Mn atom rathe r than on a Pd atom. This result is interpreted in terms of orbital interac tions by the existence of a strong interaction between the partially filled 2 pi NO orbitals and the empty d spin-orbital of Mn. NO keeps a large magn etic moment when adsorbed on surface B (0.6 mu B). (C) 1999 Elsevier Scienc e B.V. All rights reserved.