Ideal Strengths and Bonding Properties of PuO₂ under Tension

We perform a first-principles computational tensile test on PuO₂ based on density−functional theory within a local density approximation (LDA)+U formalism to investigate its structural, mechanical, magnetic and intrinsic bonding properties in four representative directions: 001, 100, 110 and 111. The stress−strain relations show that the ideal tensile strengths in the four directions are 81.2, 80.5, 28.3 and 16.8 GPa at strains of 0.36, 0.36, 0.22 and 0.18, respectively. The 001 and 100 directions are prominently stronger than the other two directions since more Pu–O bonds participate in the pulling process. By charge and density of state analysis along the 001 direction, we find that the strong mixed ionic/covalent character of the Pu–O bond is weakened by tensile strain and PuO₂ will exhibit an insulator-to-metal transition after tensile stresses exceeding about 79 GPa.