Electronic processes in fast thermite chemical reactions: A first-principles molecular dynamics study

Rapid reaction of a molten metal with an oxide is the key to understanding recently discovered fast reactions in nanothermite composites. We have investigated the thermite reaction of Fe₂O₃ with aluminum by molecular dynamics simulations with interatomic forces calculated quantum mechanically in the framework of the density functional theory. A redox reaction to form iron metal and Al₂O₃ initiates with the rapid formation of Al-O bonds at the interface within 1 ps, followed by the propagation of the combustion front with a velocity of 70 m/s for at least 5 ps at 2000 K. The reaction time for an oxygen atom to change character from Fe₂O₃ type to Al₂O₃ type at the interface is estimated to be 1.7±0.9 ps, and bond-overlap population analysis has been used to calculate reaction rates.