First-principles study of energetic and electronic properties of A2Ti2O7 (A=Sm, Gd, Er) pyrochlore

First-principles calculations have been carried out to study the electronic properties of A2Ti2O7 (A=Sm, Gd, Er) pyrochlores. It was found that f electrons have negligible effect on the structural and energetic properties, but have significant effect on the electronic properties. Density of state analysis shows that A-site 4f electrons do take part in the chemical bonding. Also, we found that ⟨Gd-O48f⟩ bond is less covalent than ⟨Sm-O48f⟩ and ⟨Er-O48f⟩ bonds, while ⟨Ti-O48f⟩ bond in Gd2Ti2O7 is more covalent. It was proposed that for A2Ti2O7 (A=Sm, Gd, Er) pyrochlores, ⟨Ti-O48f⟩ bonds may play more significant role in determining their radiation resistance to amorphization.