Atomistic level relativistic quantum modelling of plutonium hydrogen reaction

We have computed the electronic structural and spectroscopic properties for the low-lying electronic states of plutonium hydrides, PuHn (n = 2–4) and their ions which provide significant insight into plutonium hydriding reactions. We have employed a relativistic quantum technique that uses relativistic effective core potentials on Pu. Our computations show that whereas PuH2 and PuH3 form stable C2v and C3v structures which exhibit Pu–H direct chemical bonds, PuH4 becomes a complex of PuH2 with a partially dissociated H2. Our computations show that the H2 dissociation is assisted by PuH2. Electron density contour maps including Laplacians of charge densities support that the Pu site of the hydrided species is depleted substantially in charge thereby causing catalysis of further hydriding. The IR spectra show that the H2 sorbed on PuH2 is partially dissociated. We have also provided comparison of our results with corresponding computations on uranium hydrides.