First-Principles Study of Properties of Alpha Uranium Crystal and Seven Alpha Uranium Surfaces

Abstract

First-principles calculation based on the GGA methods has been applied to the prediction of the properties of bulk -uranium and seven -uranium surfaces. The number of layers in the slab has great effects on the simulated surface properties. The predicted surface properties are trustworthy when the slab number is nine or more. The surface energies of the seven low index uranium surfaces are in the range from 1.756 to 2.151 J/m 2 . The hybrid between the 5 orbital and 6 orbital also has somewhat impacts on the surface energies of uranium.

Elucidating the Initial Steps in α-Uranium Hydriding Using First-Principles Calculations

“…Here, we chose the (001) surface as this is the most stable α-U facet. The experimental surface energy of α-U is 1.828 J/m 2 ; however, this value corresponds to an isotropic crystalline structure of the metal or an average value of different surfaces . Since the (001) facet has the lowest energy, it would be the most abundant surface in the uranium crystalline material.…”

“…The experimental surface energy of α-U is 1.828 J/m 2 ; however, this value corresponds to an isotropic crystalline structure of the metal or an average value of different surfaces. 19 Since the (001) facet has the lowest energy, it would be the most abundant surface in the uranium crystalline material. As presented in Table 2, the descending order of the surface energy for various functionals is RPBE_D3BJ > PBE_D3BJ > PBEsol > PBE > SCAN.…”

“…, a single hydrogen atom per surface) using DFT. For example, some results exist regarding surface energies, single atom/molecule geometries, point defect formation energies in the bulk, and adsorption energies on the (001) surface (generally considered to be the most stable). − While these studies provide useful information about the very first steps of the hydriding process (including H 2 dissociation), the effects of strain, concentration and partial pressure of hydrogen, and ML coverage remain entirely unknown. Hence, our effort is the most in-depth ab initio study of U–H interactions as well as the uranium hydriding phase diagram that we know of to date.…”

Two-Dimensional Nanomaterials as Anticorrosion Surface Coatings for Uranium Metal: Physical Insights from First-Principles Theory

“…All the calculations were performed with the Vienna Ab Initio Simulation Package (VASP) version 5.4.4. , The projector-augmented wave (PAW) method and Perdew–Burke–Ernzerhof (PBE) exchange-correlation functional were employed . Previous studies have demonstrated that GGA functionals could accurately describe the electronic structure of 5f metals including U and plutonium (Pu). − It has also been shown that DFT+ U calculations with Hubbard correction on 5f orbitals of U significantly overestimate the atomic volume of U metal and alloys . Therefore, we selected the PBE functional in this work.…”

Bulk and surface diffusion of neodymium in alpha-uranium: Ab initio calculations and kinetic Monte Carlo simulations

“…To this end, we have employed in this study a combination of ab initio density functional theory (DFT) calculations and kinetic Monte Carlo (KMC) simulations to predict the bulk diffusivity of Nd through a-U, fully taking into account the effect of radiation enhanced diffusion. We have further considered the migration of Nd adatoms on the a-U (001) surface, which is the most stable (i.e., having the lowest surface energy) among seven low index surfaces considered by Huang and Ju [7]. Importantly, the temperature-dependent bulk and surface diffusivities of Nd in a-U calculated here using lower length scale simulations, together with the diffusion coefficients of Nd in liquid Na/Cs from Li et al [4,5], can be used to parameterize mesoscale phase-field simulations using the MARMOT code [8] to determine the effective diffusivity of Nd through a-U fuel with a porous microstructure.…”