  We derive a simple analytical line integral expression for the relaxation
volume tensor of an arbitrary interconnected dislocation network. This quantity
determines the magnitude of dislocation contribution to the dimensional changes
and volumetric swelling of a material, and highlights the fundamental dual role
of dislocations as sources of internal strain as well as carriers of plastic
deformation. To illustrate applications of the method, we compute the
relaxation volume of a stacking fault tetrahedron, a defect commonly occurring
in fcc metals; the volume of an unusual tetrahedral configuration formed by the
(a/2)<111> and a<001> dislocations in a bcc metal; and estimate the relative
contribution of extended dislocations to the volume relaxation of heavily
irradiated tungsten.
