THRESHOLD DISPLACEMENT ENERGY FOR SINGLE CRYSTAL OF BERYLLIUM

Abstract

The proposed work is to evaluate the threshold displacement energy in pure hcp crystal of beryllium using ab-initio molecular dynamics. Beryllium is a lightweight metal with unique nuclear properties that makes it more desirable material as a neutron multiplier material for tritium breeding blanket in the future reactor, where it will be subjected to high-energy neutron irradiation. Most of the research is focused around zirconium, silicon carbide, tungsten whereas literature is almost mute with respect to the exact value of threshold displacement energy for beryllium. Threshold displacement energy is one of the fundamental input parameters to ascertain the amount of damage in the beryllium under the influence of neutron irradiation. The value of threshold displacement energy is evaluated along the center of the three main high-symmetry lenses. We further determined three more displacement energies slightly off the center of the lens to study the direction dependence of the threshold displacement energy. We have also compared the simulation results with the experiment of isochronal recovery of electrical resistivity of beryllium. This is a reasonable, justified well founded validation of the threshold displacement energy calculated from the ab-initio molecular dynamic simulation. The Molecular dynamics simulation employs an empirical potential to calculate the interatomic interaction which is not based on quantum mechanics due to which we have an incorrect prediction of threshold displacement energy. With the help of the Vienna ab initio simulation package (VASP), we have predicted the threshold displacement energy based on quantum mechanics.