Structures and potential energy functions for ground states of PuU and U_2 molecules

Pu-Pu,Pu-U and U-U interatomic potentials must be known in molecular dynamics (MD) calculation of the effects of U recoil nucleus produced by self irradiation on physical properties and phase stability in δ-Pu.Because of the lack of experimental data for fitting Pu-U and U-U potentials,electronic states and potential data of PuU and U2 molecules are obtained by ab initio calculations with B3LYP hybrid exchange-correlation functional.The valence electrons of Pu and U atoms are treated with contraction basis sets,and the cores are approximated with relativistic effective core potential.The results show that electronic states for the ground states are X11Σu+ and X9Σg+.The pair potential data are fitted with the Murrell-Sorbie analytical potential function.The LDA+U calculations on the Pu-U intermetallic compound are performed with Perdew and Wang exchange-correlation functional at the spin-polarized level.The material parameters,such as the cohesive energies,elastic constants,and bulk modulus,are used to fit the 0-K universal Rose EOS,so the Pu-U EAM potential model is obtained.