Electronic structure and properties of FeO{sub n} and FeO{sub n}{sup {minus}} clusters
- Virginia Commonwealth Univ., Richmond, VA (United States). Physics Dept.
Studies of iron oxide clusters are particularly important not only because the interaction of iron with oxygen is of great interest in understanding corrosion but also because iron oxide plays a central role in the transport of oxygen in biological systems. The electronic and geometrical structures of the ground and some excited states of the FeO{sub n} and FeO{sub n}{sup {minus}} clusters (n = 1--4) have been calculated using the density-functional theory with generalized gradient approximation for the exchange-correlation potential. It is found that the multiplicity of the ground states decreases with increasing n, and the ground states of FeO{sup {minus}} and FeO{sub 2}{sup {minus}} are quartets whereas those of FeO{sub 3}{sup {minus}} and FeO{sub 4}{sup {minus}} are doublets. All of these anions possess isomers with different spatial or spin symmetries that are close in energy to their ground states. For example, FeO{sub 4}{sup {minus}} has at least five stationary states that are stable against electron detachment and fragmentation. Calculated adiabatic electron affinities (A{sub ad}) of FeO, FeO{sub 2}, and FeO{sub 3} are within 0.2 eV of the experiment. FeO{sub 4} was found to be a particularly interesting cluster. Although its neutral precursor possesses a closed electronic shell structure, it has an A{sub ad} of 3.8 eV, which is higher than the electronic affinity of halogen atoms. The experimental estimate of 3.3 eV for the A{sub ad} of FeO{sub 4} is shown to originate from the detachment of an electron from one of the higher-energy isomers of the FeO{sub 4}{sup {minus}} cluster. The energetically preferred dissociation channels of FeO{sub 2}, FeO{sub 3}, FeO{sub 4}, FeO{sub 3}{sup {minus}}, and FeO{sub 4}{sup {minus}} correspond to abstraction of an O{sub 2} dimer but not to an Fe-O bond rupture. FeO{sub 3}{sup {minus}} and FeO{sub 4}{sup {minus}} are found to be thermodynamically more stable than their neutral closed-shell parents, and FeO{sub 3}{sup {minus}} is the most stable of all the clusters studied. The existence of several low-lying states with different multiplicities in FeO{sub n} and FeO{sub n}{sup {minus}} indicates that their magnetic properties may strongly depend on temperature.
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- FG02-96ER45579
- OSTI ID:
- 682157
- Journal Information:
- Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory, Vol. 103, Issue 29; Other Information: PBD: 22 Jul 1999
- Country of Publication:
- United States
- Language:
- English
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