Tuning the electronic properties of C12A7 via Sn doping and encapsulation

Abstract

AbstractCation doping in electride materials has been recently considered as a viable engineering strategy to enhance the electron concentration. Here we apply density functional theory-based energy minimisation techniques to investigate the thermodynamical stability and the electronic structures of Sn-doped and Sn-encapsulated in stoichiometric and electride forms of C12A7. The present calculations reveal that encapsulation is exoergic and doping is endoergic. The electride form is more energetically favourable than the stoichiometric form for both encapsulation and doping. Encapsulation in the electride results a significant electron transfer (1.52 |e|) from the cages consisting of extra-framework electrons to the Sn atom. The Sn forms almost + 4 state in the doped configuration in the stoichiometric form as reported for the electride form in the experiment. Similar charge state for the Sn is expected for the electride form though the extra-framework electrons localised on the Sn. Resultant complexes of both forms are magnetic. Whilst significant Fermi energy shift is noted for the doping in C12A7:O2− (by 1.60 eV) towards the conduction band, there is a very small shift (0.04 eV) is observed in C12A7:e−. Future experimental study on the encapsulation of Sn in both forms of C12A7 and doping of Sn in the stoichiometric form can use this information to interpret their experimental data.