First-principles study on the doping effects of Al in α-MnO2

• Al substitution reaction is easier to occur in the α-MnO2.
• AlxMn1−xO2 is more stable under the O-rich growth condition.
• Al doping can afford acceptor impurity level which can accommodate electron.

In this paper, first-principles calculations have been implemented to study the structural relaxation, formation energies and electronic structure of Al doped α-MnO2. Both Al insertion and Al substitution reactions in the α-MnO2 were considered. Calculated formation energies indicate that Mn atom is easier to be displaced by Al atom under the O-rich growth condition compared with Al insertion reaction. Besides, it can be found that Al doping can afford acceptor impurity level which can accommodate electrons, thus contributing to the improvement of conductivity of α-MnO2. The conductivity of α-MnO2 is gradually improved with the increasing doping concentration of Al, and Al0.0417Mn0.9583O2 exhibits the best conductivity. Lastly, the electronic structure of Al0.0417Mn0.9583O2 was further investigated by analysis of total charge density and Bader charge. It is clear that Al doping can afford more electrons for α-MnO2, which also contributes to improvement of its conductivity.

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