  To simulate a macroscopic system from a simulation cell, a direct summation
of the elastic fields produced by periodic images can be used. If the cell
contains a non-zero elastic dipole component, the sum is known to be
conditionally convergent. In analogy with systems containing electric or
magnetic dipoles, we show that the sum introduces a component which only
depends on the shape of the summation domain and on the dipole density. A
correction to the direct summation is proposed for the strain and stress fields
in the simulation cell, which ensures that zero tractions are imposed on the
boundary of the macro-scopic system. The elastic fields then do not depend
anymore on the shape of the domain. The effect of this correction is emphasized
on the kinetics of dislo-cation loop growth by absorption of point defects. It
is shown that correcting elastic fields has an influence on the kinetics if
defects have different properties at stable and saddle points.
