Evolution of Small Copper Clusters and Dissociative Chemisorption of Hydrogen

Abstract

The structural evolution of small copper clusters of up to 15 atoms and the dissociative chemisorption of H2 on the minimum energy clusters are studied systematically using density functional theory. The preferred copper sites for chemisorption are identified and the transition state structures and activation barriers for clusters four to nine atoms are determined and found to be inconsistent with the empirical Bronsted-Evans-Polanyi relationship. The physicochemical properties of the clusters are computed and compared with the bulk and surface values. The results indicate that a phase transition must occur in the going from cluster to bulk.

Optical absorption of small copper clusters in neon: Cun, (n = 1–9)

“…We find in agreement with previous DFT calculations 21,29,43,44,46,52,53 that the T d and D 2d geometries are close in energy. Cu 8 is a special case since in the jellium model it corresponds to a closed shell cluster.…”

“…Our DFT calculation, as well as recent calculations, 29,44,46,52,53 find that the ground state configuration is the three-dimensional D 5h structure, lying just below the C 3v structure. The low energy part of the spectrum, of s-s type, corresponds well with the calculation for the D 5h structure if we include a shift of ∼0.2 eV.…”

“…48 and 49) or DFT (Refs. 29,[43][44][45][46][50][51][52][53] schemes. All recent calculations agree that the planar D 2h geometry corresponds to the ground state structure.…”

“…Different DFT calculations were performed on this system, 29,43,44,46,[51][52][53] all of them including ours find the planar D 3h structure to be the most stable isomer, in close competition with the C 5v and C 2v three-dimensional structures. The analysis indicates, such as in the case of Cu 5 , that the low energy transitions, typically below 3 eV, are issued of the predominantly s-type HOMO Kohn-Sham orbital, while they are of of d-s type between 3 and 5 eV and of d-p type above 5 eV.…”

Enhanced magnetism of Cun clusters capped with N and endohedrally doped with Cr

“…It is to be noted that previous works on small copper clusters indicate a rich variety of structures and the icosahedral symmetry based structure is predicted not to be the true ground state structure for a Cu 13 cluster. [26,35] Our calculated total binding energy and magnetic moment for the locally optimized three structures of the Cu 13 cluster, are 29.05 eV and 5 µ B respectively for the optimal ICO structure, 29.53 eV and 1 µ B respectively for the optimal HBL structure and finally, 29.65 eV and 1 µ B respectively for the optimal BBP structure. So it is the optimal BBP structure of a pure Cu 13 cluster which appears as its MES in our calculations.…”