Calculation of Helium Dissociation Energies for Vanadium, Niobium and Molybdenum by a Computer Simulation Method

Abstract

Atomistic calculations of activation energies of helium dissociation from helium-vacancy clusters in vanadium, niobium and molybdenum have been performed by a computer simulation method. In the process, formation energies of vacancy clusters, interstitial helium and helium-vacancy clusters have been also calculated as well as migration energies of vacancy and helium. Potentials of metal-metal and helium-metal for vanadium and molybdenum were after Johnson and Wilson, whereas other potentials were constructed in a similar manner. Calculated dissociation energies in vanadium and niobium are around 3.0 eV and smaller than those in molybdenum (4.0 eV to 5.0 eV). Large helium dissociation energies from small clusters suggest stable agglomeration states of helium in these bcc metals.