Structures and potential energy functions of Pu-3 molecule

Density functional (B3LYP) method with relativistic effective core potentia l (RECP) has been used to optimize the structures of Pu-2 and Pu-3 molecule s. The results show that the ground states of Pu-2 and Pu-3 molecules are o f D-infinityh and D-3h symmetry, and of 13 and 19 fold, respectively. The s pectral constants of Pu-2, omega (e) = 52.3845 cm(-1) and omega (e)chi (e) = 0.0201 cm(-1), and the harmonic frequencies of Pu-3,nu (1) = 56.9007 cm(- 1), nu (2) = 57.1816 cm(-1) and nu (3) = 64.0785 cm(-1), have also been obt ained on the B3LYP/RECP level. The potential energy functions of Pu-2 and P u-3 have been derived, for the first time so far as we know, from normal eq uation fitting and the many-body expansion theory.