Knowledge Bank

During the last years in our group we have been studying the actinyl ions, their electronic spectra, symmetric-stretch vibrational frequencies and actinide-oxygen (An-O) equilibrium distances. Most experimental results, though, exist in solid or liquid phase, so a direct comparison between our previous theoretical results and experimental results is not plausible. For this reason, we have modeled the $Cs2UO2Cl4$ crystal in which both the uranyl and neptunyl spectra have been observed. The central atom, uranium or neptunium and the closest oxygens and chlorines are treated with Relativistic Effective Core Potentials(RECPs) and basis sets, the closet cesiums are treated with all electron potentials and the rest of the crystal with point charges. We performed spin-orbit Graphical Unitary Group Approach (GUGA) Configuration Interaction calculations, similar to the ones for the free ions. The An-O bond distances in the crystal increase by approximately $0.07\backslash AA$ compared to the free ions and the symmetric stretch vibrational frequencies decrease by about $200cm-1$. It seems that most of the previous differencies between theory and experiment are due to the crystalline environment rather than the insufficiency of theory.