Theoretical investigation of structural, energetic and electronic properties of titanate pyrochlores

Abstract

Ab initio total energy calculations using the plane-wave pseudopotential method based on density functional theory were carried out to investigate the structural, energetic and electronic properties of A2Ti2O7 (A = La, Gd and Yb) pyrochlores. It turned out that the formation energies of antisite defects are not linearly dependent on the ratio of the cation radii, and, for the three compositions, the cation antisite formation energy is largest for Gd2Ti2O7 pyrochlore. It was indicated that Gd2Ti2O7 compound is the least likely to form defect fluorite structure, which gives rise to the least resistance to radiation-induced amorphization. DOS analysis showed that stronger interaction exists in the Gd2Ti2O7 compound, and its electronic structure is very different from that of La2Ti2O7 and Yb2Ti2O7. Our calculations suggested that the electronic structure of the A cation and bond type should be taken into account when explaining the response behavior of A2Ti2O7 (A = La, Gd, Yb) pyrochlores to ion irradiation-induced amorphization.