Method for calculating alloy energetics

ORDERING AND SEGREGATION IN BIMETALLIC Fe–Pt NANOPARTICLES

Atomistic modeling of bimetallic Fe–Pt nanoparticles is performed using the BFS method for alloys. A simple approach is introduced to analyze segregation to the surface and bulk ordering patterns as a function of particle size and composition.

ATOMISTIC MODELING OF THE FORMATION AND STABILITY OFNiANDVNANOWIRES ON A STEPPEDRh(553)SUBSTRATE

The formation and stability of Ni and V nanowires on a stepped Rh(553) substrate is investigated using the BFS method for alloys via an atom-by-atom description of the formation process. In agreement with experiment, Ni is found to form one-dimensional wires attached to the surface steps, while V does not. However, a detailed analysis of the energetics reveals that there the apparent differences leave room for the possibility of alloying in the case of Ni and the formation of structures along the step in the case of V .

Atomistic Simulation of High-Density Uranium Fuels

We apply an atomistic modeling approach to deal with interfacial phenomena in high-density uranium fuels. The effects of Si, as additive to Al or as U-Mo-particles coating, on the behavior of the Al/U-Mo interface is modeled by using the Bozzolo-Ferrante-Smith (BFS) method for alloys. The basic experimental features characterizing the real system are identified, via simulations and atom-by-atom analysis. These include (1) the trend indicating formation of interfacial compounds, (2) much reduced diffusion of Al into U-Mo solid solution due to the high Si concentration, (3) Si depletion in the Al matrix, (4) an unexpected interaction between Mo and Si which inhibits Si diffusion to deeper layers in the U-Mo solid solution, and (5) the minimum amount of Si needed to perform as an effective diffusion barrier. Simulation results related to alternatives to Si dispersed in the Al matrix, such as the use of C coating of U-Mo particles or Zr instead of the Al matrix, are also shown. Recent experimental results confirmed early theoretical proposals, along the lines of the results reported in this work, showing that atomistic computational modeling could become a valuable tool to aid the experimental work in the development of nuclear fuels.

Gradient equivalent crystal theory

This paper presents an extension of the formalism of equivalent crystal theory (ECT) by introducing an electron density gradient term so that the total model density becomes a more accurate representation of the real local density. Specifically, we allow for the electron density around a lattice site to have directionality, in addition to an average value, as assumed in ECT. We propose that an atom senses its neighbouring density as a weighted sum-the weights given by the its own electronic probability. As a benchmark, the method is used to compute vacancy migration energy curves of iron. These energies are in good agreement with previously published results.