Structures and magnetic moments of Fe-C clusters

Abstract

The structures and magnetic moments of small $\mathrm{Fe}{\mathrm{C}}_{N}$ $(N=1--8)$ and ${\mathrm{Fe}}_{2}{\mathrm{C}}_{N}$ $(N=1--6)$ clusters have been obtained by all-electron density functional theory. For the $\mathrm{Fe}{\mathrm{C}}_{N}$ $(N=1--8)$ clusters, except for $\mathrm{Fe}{\mathrm{C}}_{2}$, the ground states are predicted to be linear structures with the Fe atom bonded at one end. For the ${\mathrm{Fe}}_{2}{\mathrm{C}}_{N}$ $(N=1--6)$ clusters, the lowest-energy geometries show significant odd-even alternation. The ${\mathrm{Fe}}_{2}{\mathrm{C}}_{N}$ clusters with even $N$, plus ${\mathrm{Fe}}_{2}\mathrm{C}$, have cyclic planar structures with transannular bonds. The ${\mathrm{Fe}}_{2}{\mathrm{C}}_{N}$ clusters with odd $N$ $(N=3,5)$ prefer linear geometries with the two Fe atoms at the two ends. For all the clusters, analysis of the M\"ulliken population shows charge transfers from the Fe atom(s) to the C atoms with the magnetic moment lying primarily on the Fe atom(s).