Ion irradiation experiments and atomistic simulations were used to demonstrate that irradiation-induced lattice swelling in a complex oxide, Lu2Ti2O7, is due initially to the formation of cation antisite defects. X-ray diffraction revealed that cation antisite formation correlates directly with lattice swelling and indicates that the volume per antisite pair is approximately 12  Å3. First principles calculations revealed that lattice swelling is best explained by cation antisite defects. Temperature accelerated dynamics simulations indicate that cation Frenkel defects are metastable and decay to form antisite defects.

A systematic density functional theory study is performed to investigate the lattice parameters, the internal positional parameter [Formula: see text] and bond length of RE2Sn2O7(RE = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu) pyrochlores. To analyze the structural stability in extreme conditions and verify whether bond strength varies inversely to bond length in rare-earth stannate pyrochlores, the structural parameter and bonding strength under hydrostatic pressure are studied. The tight connection between the different bond length contraction and the variation of 48[Formula: see text] oxygen positional parameter [Formula: see text] is also discovered. We calculated the bond length and the bulk modulus of RE2Sn2O7and found that the [Formula: see text]RE–O[Formula: see text] bond plays a predominant role in determining the bulk modulus. Meanwhile, the present calculations suggest that the “bimodal effect” also exists in rare-earth stannate pyrochlores.

Synthesis, characterisation and crystal structure analysis studies of oxides in (Gd 2−x Ce x )Ti 2 O 7 series have been reported, Ce 3+ used as a surrogate for Pu 3+ because they have similar physical and chemical properties. In the present report, a series of pyrochlore-type crystal with composition (Gd 2−x Ce x )Ti 2 O 7 (0 ≤ x ≤ 0.8) were successfully synthesised by the solution combustion followed by high temperature calcining. The phase purity and crystal structure of samples were investigated by X-ray diffraction analysis as well as Rietveld refinement. It was observed that the solubility of Ce 3+ in the lattice of Gd 2 Ti 2 O 7 pyrochlore is 39.62 mol.-%. The calculated lattice parameters and the simulated XRD patterns of (Gd 2−x Ce x )Ti 2 O 7 (x = 0, 0.5, 1) were obtained based on the density functional theory. The results of theoretical calculation are quite consistent with the results of the experiment. Additionally, the grain size and the visual information about the microscopic structure of the (Gd 2−x Ce x )Ti 2 O 7 crystals were obtained by transmission electron microscopy.

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