Quantum Size Effects in the Electronic Structure Properties of γ-U (100) Nanolayers

摘要

The generalized gradient approximation (GGA) to density functional theory (DFT) and hybrid density functional theory have been used to compute the layer-by-layer properties of γ-uranium (γ-U) in the (100) symmetry. Guided by bulk results which have been analyzed at six different levels of theory, the surface calculations have been performed at the non-magnetic level including spin-orbit coupling. The ground state bulk lattice constant and bulk modulus are found to be 3.46 A and 113.75 GPa, respectively at the non-magnetic with spin-orbit coupling level (NM+SOC) of theory. The monolayer displays a significant shrinking of the "effective" lattice constant of about 23.55% from bulk theoretical values. Further analysis of the change in energy per added "bulk" indicates that after 5 layers the energy stabilizes and does not change by more than 10 mRy. The surface energy and the work function of the γ-U (100) surface are predicted to be 1.56 J/m~2 and 3.24 eV respectively. Electronic density of states plots of atoms located at the surface, subsurface and center of a hexa-layer slab indicate some localization of the 5f electrons at or near the Fermi level with a gradual trend toward delocalization with increased depth within the slab.