Volume changes in copper due to point defects

Isotropic linear elasticity theory is used to calculate the volume change due to point defects and the pressure of atomistic helium bubbles. Atomistic defect calculations for the specific case of helium in copper are used to illustrate the technique. It is found that helium atoms introduced into vacancies in copper produce a volume increase of ∼0.62 atomic volumes per helium atom. However, this linear increase is found only after the number of helium atoms is greater than the number of vacancies. The pressure of helium as a function of density is also calculated. Extremely high pressures are found for the high densities considered; it is found that the pressure increases nearly linearly with density.