摘要
Superexchange effects play an important role in the determination of crystal structures; however, there has been much less reported on how they determine the stability of dusters. Using evolutionary search strategies and DFT＋U （density functional theory with the Hubbard U correction） calculations, we investigate the global minimum-energy structures of Fe12O12 clusters. Among predicted Fe12O12 dusters, a cage-shaped Fe12O12 cluster with unexpected stability was observed. In addition, the bare Fe12O12 cluster is shown to possess an extremely large energy gap （2.00 eV）, which is greater than that of C60, Au20 and Al13- clusters. Using a Heisenberg model, we traced the origin of the unexpected stability of the bare Fe12O12 cluster to magnetic competition between the nearestneighbor exchange constant h and the next-nearest neighbor exchange constant J2 that was induced by the superexchange interactions. The bare Fe12O12 cluster is thus a unique molecule that is stable and chemically inert.
Superexchange effects play an important role in the determination of crystal structures; however, there has been much less reported on how they determine the stability of dusters. Using evolutionary search strategies and DFT＋U （density functional theory with the Hubbard U correction） calculations, we investigate the global minimum-energy structures of Fe12O12 clusters. Among predicted Fe12O12 dusters, a cage-shaped Fe12O12 cluster with unexpected stability was observed. In addition, the bare Fe12O12 cluster is shown to possess an extremely large energy gap （2.00 eV）, which is greater than that of C60, Au20 and Al13- clusters. Using a Heisenberg model, we traced the origin of the unexpected stability of the bare Fe12O12 cluster to magnetic competition between the nearestneighbor exchange constant h and the next-nearest neighbor exchange constant J2 that was induced by the superexchange interactions. The bare Fe12O12 cluster is thus a unique molecule that is stable and chemically inert.
基金
This work was supported by the National Natural Science Foundation of China （No. 11474004）, the National Science Foundation of Henan Province （No. 162300410001） and the Natural Science Foundation of Shaanxi University of Technology （No. SLGQD2017-13）.
