Theoretical elastic stiffness, structure stability and thermal conductivity of La2Zr2O7 pyrochlore

Elastic stiffness and electronic structure of La2Zr2O7 were calculated by means of the first-principles pseudopotential total energy method. The equation of state (EOS), elastic parameters (including the full set of second-order elastic coefficients, bulk modulus and Young’s modulus) and elastic anisotropy were reported. Furthermore, pressure dependence of crystal structure, electronic structure, and bond strengths were investigated. It is found that, although the La2Zr2O7 lattice is stable at high pressures, its electronic structure and atomic bonding are definitely disturbed by the applied pressure. The crystal structure of La2Zr2O7 approaches that of the fluorite-type lattice at high pressures. The strengths of different interatomic bonds in La2Zr2O7 are examined by considering bond-length contractions at various pressures. In addition, the results based on quantum-mechanical-scale calculation clarify the nature of low thermal conductivity of La2Zr2O7 at elevated temperatures.