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-O_48f> bond is less covalent than <Sm-O_48f> and <Er-O_48f> bonds, while <Ti-O_48f> bond in Gd₂Ti₂O₇ is more covalent. It was proposed that for A₂Ti₂O₇ (A=Sm, Gd, Er) pyrochlores, <Ti-O_48f> bonds may play more significant role in determining their radiation resistance to amorphization. [ABSTRACT FROM AUTHOR]