The follow information is reproduced from:

"Aryanpour, M.; van Duin, A. C. T.; Kubicki, 
J. D. J. Phys. Chem. A 2010, 114, 6298-6307"

- The initial force field parameters for the 
Fe-Fe parameters were taken from an 
earlier force field development 
project on bulk-iron metal, based on 
DFT-calculations on antiferromagnetic 
BCC and FCC. The DFT data can 
be found in Ref 31 of the above-mentioned manuscript. 
The O/H parameters were taken from the ReaxFF bulk 
water description. The Fe/Fe and O/H parameters were 
kept fixed to these initial values,
whereas the Fe/O parameters were reoptimized 
against the quantum mechanical results 
presented in the above-mentioned manuscript.

- Detailed information on the force field parameters 
is given in the supporting information of the above mentioned
manuscript.