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 <i>equation of state</i> (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