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As a 1.8 nm ZnSe nanocrystal is progressively doped with 1%, 5%, and 10% Fe, it shows a progressive change in its magnetic properties from a superparamagnetic FM‐dominated exchange type to an onset of AFM exchange with evidence of spin frustration. Magnetization measurements allow to obtain exchange coupling constants that are compared to the results of a Broken‐Symmetry Density Functional Theory (BS‐DFT) model of a doped (ZnSe)₃₄cluster. DFT shows a capability to reproduce the experimental pattern of the increasing influence of AFM exchange as doping concentration increases. The material phase segregates at the edges where strained rhombic surface sites are the preferred doping sites of iron. Large concentrations of iron leads to the formation of Fe clusters and complex exchange patterns that result in spin frustration in some iron trimers but none in the others. The spin frustration of these complex systems by assuming mirror symmetry of the sites when fitting by using BS‐DFT formalism is classified and analyzed. While some individual J constants obtained have significant errors, the averaged exchange constants are generally in good agreement with our experimental data.

Dissociation of CO₂on iron clusters was studied by using semilocal density functional theory and basis sets of triple‐zeta quality. Fe₂, Fe₄, and Fe₁₆clusters were selected as the representative host clusters. When searching for isomers of Fe_nCO₂,n=2, 4 and 16 corresponding to carbon dioxide attachment to the host clusters, its reduction to O and CO, and to the complete dissociation, it was found that the total spin magnetic moments of the lowest energy states of the isomers are often quenched with respect to those of initial reagents Fe_n+CO₂. Dissociation pathways of the Fe₂+CO₂, Fe₄+CO₂, and Fe₁₆+CO₂reactions contain several transition states separated by the local minima states; therefore, a natural question is where do the spin flips occur? Since lifetimes of magnetically excited states were shown to be of the order of 100 fs, the search for the CO₂dissociation pathways was performed under the assumption that magnetic deexcitation may occur at the intermediate local minima. Two dissociation pathways were obtained for each Fe_n+CO₂reaction using the gradient‐based methods. It was found that the Fe₂+CO₂reaction is endothermic with respect to both reduction and complete dissociation of CO₂, whereas the Fe₄+CO₂and Fe₁₆+CO₂reactions are exothermic to both reduction and complete dissociation of carbon dioxide. The CO₂reduction was found to be more favorable than its complete dissociation in the Fe₄case.