Density functional study on cage and noncage (Fe2O3)n clusters.

Both cage and noncage structures of (Fe2O3)n (n=2–6 and 10) clusters are studied using density functional theory. All the cage structures are stable without imaginary vibrational frequency but the global minima are the noncage clusters for most cases. Our results show that oxidation of Fe4On (n<6) clusters by O2 at room temperature is exothermic, while oxidation of n≥6 clusters is endothermic. This is in qualitative agreement with an experimental observation that only Fe4On+ (n≥6) clusters are produced in a laser vaporization source under saturated O2 growth conditions. Since (Fe2O3)n clusters have high stability and different structural and bonding properties from those of the bulk Fe2O3, they may serve as good models for predicting or interpreting novel properties of Fe2O3 nanomaterials. [ABSTRACT FROM AUTHOR]