Ab initio DFT calculations for materials in nuclear research

Abstract

Currently, high performance computing is a very important tool in material science. The study of materials at the microscopic level for obtaining macroscopic properties from the behavior at atomic level is a big challenge, even more when a large number of atoms are involved in the analysis. One of the most important open source codes capable of performing ab initio density functional theory (DFT) calculations with many hundreds of atoms at low computational cost is the SIESTA code. This code is able to perform self-consistent electronic structure simulations based on DFT for very complex materials. The performance of this code is tested in this work by applying it to the study of typical core structural materials used in nuclear reactors such as Zr and Zircaloy-2. These materials are commonly used for the cladding of the fuel rods used in Light Water Reactors (LWR) and CANDU reactors. First-principles calculations for Zr, Zircalloy-2 and modified structures of them were performed with microstructural defects in order to analyze material damage. Adsorption energy of I2 on Zr (0 0 0 1) surfaces as a function of the distance is also presented. Results showed how this kind of simulations can be carried out for large systems at a relatively cheap computational cost.