The defect structure of lithiated tin- and titanium-doped α-Fe2O3 has been assessed using interatomic potential calculations. Of the models considered for lithiation, a model in which Li+ occupies an interstitial site balanced by the reduction of Fe3+ to Fe2+ on an Fe3+ site was found to be more favourable than the substitution of Li+ on an Fe3+ octahedral site balanced by an O2- vacancy. Insertion of lithium into the interstitial site between two adjacent M4+ ions was particularly favourable. The calculated lattice parameters decrease on lithiation as has been observed experimentally.
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