Calculation of Vacancy Properties in Pure U

Abstract

Se estudian las propiedades estáticas y dinámicas de la vacancia en U puro a partir de técnicas computacionales a nivel atómico. El potencial de muchos cuerpos utilizado reproduce la estabilidad de la fase α (ortorrómbica) a bajas temperaturas y una transformación a la fase γ (bcc) a temperaturas más altas. Se calcula la energía de formación de la vacancia y la contribución migratoria atómica al coeficiente de autodifusión, en ambas fases, mediante Dinámica Molecular. Se analizan los resultados obtenidos y se comparan con resultados de cálculos anteriores y valores experimentales disponibles en la literatura. Palabras clave: Vacancia, Uranio, Difusión, Potencial EAM Vacancy static and dynamic properties are studied by computational techniques in pure uranium. The many-body potencial reproduces the stability of the α-phase (orthorrombic) at low temperatures and the transformation to the γ-phase (bcc) at higher temperatures. The vacancy formation energy and the atomic migration contribution to the diffusion coefficient are calculated in both phases by Molecular Dynamics. The results reached are analised and compared with previous calculations and experimental results available in the literature.

On the accurate description of uranium metallic phases: a MEAM interatomic potential approach

“…The potential reproduces a simplified αU ↔ γ U allotropic transformation and melting at temperatures relatively close to the experiment. Previous EAM potentials [23][24][25]27] are similar to the present one in that they all predict that αU is the ground state and γ U and liquid phases show up at increasing temperatures, although they tend to underestimate the αU ↔ γ U transformation temperature further. The simulations performed suggest a new alternative mechanism for this allotropic transformation, different from that of Burgers which was proposed in the literature but still not confirmed [11,56].…”

First-principles study of bubble nucleation and growth behaviors in α U–Zr

“…Although the configuration shown in figure 5 seems to be rather complicated, it can be understood easily with the help of structure visualization software. The configuration and corresponding binding energy can be used to build an appropriate potential for classic molecular dynamics [5,[43][44][45][46][47][48][49][50][51], and also provide a foundation for further first-principles calculations in the future.…”

Interatomic potential for uranium in a wide range of pressures and temperatures

“…To our knowledge, there exist three published interatomic potentials for uranium [30][31][32][33]. All of them are developed as central-force many-body potentials [34][35][36][37][38] commonly referred to as embedded atom method (EAM) potentials [34,35].…”

“…The construction of the above-mentioned potentials for U [30][31][32][33] was based on simple analytical forms of the ϕ, ρ and F functions. The potential of Pascuet et al [30,31] was fitted to the lattice constants, the equilibrium atomic volume, the bulk modulus and the cohesion energy of α-U. The embedding function F was obtained from the universal features of the equation of state of metals.…”