Theoretical Studies Of Actinide Halide Nitrogen Ligand Structure And Electronic Properties

Structures and properties of actinide complexes have provided theoretical understanding for their application in abstracting nuclear fuel, re-using spent fuel and storing nuclear waste. Actinide atoms contain a large number of electrons and their complexes have access to diverse bonds. And thus, electron correlation effect, relativistic effect and environment effect have to be significantly considered for their accurate calculations. This has presented a challenge for theoretical investigation. In this thesis, a series of N-coordinated actinide halides have been designed and calculated using scalar relativistic density functional theory (DFT). Associated with experimental results, we studied effects of changing N-donors from mono-, di-to tridentate, actinyl (sorts:U, Np and Pu; number:mono-and binuclear; oxidation state: Ⅵ and Ⅴ) as well as halide (F, Cl, Br and I) on electronic structures, vibrational spectra, electronic spectra and thermodynamical reaction properties. The study has revealed the nature of triple-bond of An=O. The electronic feature is elucidated that actinyl halides have low-lying f(U)-character unoccupied orbitals and characteristic σ(U=O)+π(X) occupied orbital whose energy is stabilized upon increasing halide donating ability. The regularity of synthetic reaction of complexes is rationalized. In brief, this work has provided foundation for experimental synthesis of actinides and their further application in nuclear industry.