Molecular Structure Of Plutonium Compounds, The Potential Energy Function And Molecular Reaction Dynamics,

Density functional Becke 3LYP method with relativistic effective core potential (RECP) and Gaussian 98W program have been used to investigate the structures and potential energy functions of plutonium compounds, and to investigate the geometrical configurations and stability of PuN(n=2,3,4) molecules. The atomic and molecular reaction dynamic processes for the reaction systems of plutonium compounds have been studied based on the present potential energy functions. The mechanism for the oxidation of metallic plutonium in moisture air has been discussed.Firstly, the possible electronic states and the reasonable dissociative limits for plutonium compounds have been derived based on the atomic and molecular reaction statics and the resolution of group representations. The molecular structures for PuO, PuH, PuH2, HPuO, Pu2, Pu3 and Pu4 have been optimized based on the Density functional Becke 3LYP method. Results show that the ground electronic states for PuO, PuH, PuH2 and HPuO are X7?, X8?, X7B1 and X6A respectively.However, the reaction rate for H+PuH(v-0,j=0) is far more lower comparing with that for Pu+H2(v=0,j=0). Secondly, the Murrell-Sorbie potential energy functions for the diatomic molecules PuO and PuH have been obtained according to the ab initio data through the least square fitting. The spectroscopic constants for PuO and PuH have been derived from the potential energy functions. The analytic potential energy functions for ground states of PuH2 and HPuO molecules have also been derived by many-boy expansion method using their equilibrium geometry structure parameters, dissociation energy and force constants of the tri-atomic molecules. Figures for the potential energy functions have bee given. These potential energy functions show the structure characteristics of the molecules exactly.Thirdly, the atomic and molecular reaction dynamic processes for the collisions system of Pu+H2 and H+PuH have been studied based on the present potential energy function of PuH2 by Monte-Carlo puasi-classical trajectory approach. It is can be concluded from the relationship between the initial energy and the reaction sections that Pu+H2(v=0,j=0) has no energy threshold, and the principal product of this reaction is PuH2. However, the energy threshold for H+PuH(v=0,j=0) is 47.8kcal.mol-1, and the reaction rate for H+PuH(v=0,j=0) is far more lower comparing with that for Pu+H^2(v=0,j=0)). The results also show that the reaction section for Pu+H2(v=0,j=0) decrease rapidly with the initial energy increasing. When the initial energy is over 251.04kJ.mol-1, the molecular reaction dynamic processes are mainly non-reaction. The results are good in agreement with the equilibrium pressure observed in the decomposition process of PuH2.The atomic and molecular reaction dynamic processes for the collisions systems of Pu+HO(v=0,j=0), H+PuO(v=0,j=0) and O+PuH(v=0,j=0) have also been studied. The results show that both Pu+HO and O+PuH have no energy threshold, and the principal products of these reactions are mainly PuO. However, H+PuO is a non-reaction process. The results also show that the reaction rate for PuH+O is very fast if PuHx exit in the reaction system. These conclusions are good in agreement with the experimental results observed in the investigation of metallic plutonium oxidation in air where small amount of PuHx exits. Our theoretical investigation results gives a reasonable explain for the experiment results. It is of great significance for the more understanding the oxidation corrosive mechanism of metallic plutonium in moisture air.The dissociation energy and harmonic force constants for Pu2 and Pu3 have been calculated for the first time. The potential energy functions for Pu2 and Pu3 have also been obtained.Then, we have found the spin-polarization effect in Pun(n=2,3,4) for the first time. The valence electrons of Pu are six. The non-pair electrons for Pu2, Pu3 and Pu4 are twelve, eighteen, and twenty-four respectively according to the present calculation. It is means that all of the valence el...