Computational Tools for Predictive Modeling of Properties in Complex Actinide Systems

This chapter focuses on methodological and computational aspects that are key to accurately modeling the spectroscopic and thermodynamic properties of molecular systems containing actinides within the density functional theory (DFT) framework. It discusses two methods that account for relativistic effects, the zeroth-order regular approximation (ZORA) and the eXact 2-Component (X2C) Hamiltonian. The chapter also discusses the implementation of the approximate relativistic ZORA Hamiltonian and its extension to magnetic properties. It also focuses on the exact X2C Hamiltonian and the application of this methodology to obtain accurate molecular properties. The chapter examines the role of a dynamical environment at finite temperature as well as the presence of other ions on the thermodynamics of hydrolysis and exchange reaction mechanisms. Finally, it describes the modeling of X-ray Absorption Spectrum (XAS) (EXAFS, XANES) properties in realistic environments accounting for both the dynamics of the system and relativistic effects.