Stability of Ni Clusters and the Adsorption of CH₄: First-Principles Calculations

Abstract

Structural, magnetic and adsorption properties of Ni n ( n = 2–16, 21, 55) clusters have been investigated based on density funciontal theory (DFT) with the spin polarized generalized gradient approximation, using the Perdew–Burke–Ernzerhof functional. The most stable isomers have been selected to study the adsorption of methane CH 4 and methyl CH 3 . It is found that the CH 4 molecule adsorbs on the top site for all clusters considered. The most selective Ni n clusters are the tetrahedron ( n = 4) and icosahedral clusters due to high-coordinated edge atoms ( n = 13, 21, and 55). For CH 3, stronger adsorption tendencies were found with similar patterns. Our results show that clusters with n = 6, 10, and 13 with complete atomic shells are relatively more stable. Besides, they perform the lowest adsorption for CH 3, indicating that they possess such a desirable property of a higher carbon poisoning resistance, than for the rest of the clusters. This result can be understood in terms of the electronic stability and localization of the frontier molecular orbitals.