Lattice dynamics of actinides and actinide compounds from first-principles calculations

Abstract

Actinides are the first elements of a periodic table that contain 5f electrons. 5f electrons are unique due to their ability to be partially localized and delocalized. The ratio of localization and delocalization of 5f-states significantly affects the resulting material properties and therefore its exact determination is necessary. Also, spin-orbital interactions can play a significant role for high atomic number elements due to the increase of relativistic phenomena. Based on the well-determined localization of 5f-states through Hubbard U correction and the inclusion of spin-orbital interaction, the electron, mechanical, phonon and thermodynamic properties of thorium metal and thorium monocarbide are reproduced in this work. At the same time, the electron, mechanical, phonon and thermodynamic properties of the protactinium monocarbide are predicted because only a lattice constant being known experimentally. Research on both monocarbides is necessary because of their potential to become future nuclear fuels. The influence of the spin-orbital interaction and localization of 5f-states is discussed not only on the basis of comparison with experiments but also on comparison with other theoretical works.