Structure optimization and IR frequency interpretation of Fe6(OH)1s(H20)6 Nano particles by OFT calculations

Abstract

y-Fe203 nanopratciles were syntheised by the co-precipitation method and these particles are in 5-20 nm range in size. Plausible molecular structures (Figure 1) of Y - Fe203 were examined by density functional theory (DFT) using the cluster modelling method. Cluster configurations and IR frequency calculations of Fe6(OH)18(H20)6 were performed using the DFT hybride 83L YP function with 6-31 G (d, p) basic set. The average bond lengths of Fe-Fe and bulk Fe-O entities as 2.93 A and 1.92 A, respectively. The calculated bond lengths are comparable with the crystallographic data. Vibrational frequency calculations and experimental data are in good agreement with the observations in the range of 900 cm' t01024 cm' (Figure 2). However, OH stretching frequencies at (1640), 3000, 3500 crn' of y -Fe203 is significantly different due to H- bonding nature.