  Theoretical results on the dynamics of dislocations in Rayleigh-B\'enard
convection are reported both for Swift-Hohenberg models and the Boussinesq
equations. For intermediate Prandtl numbers the motion of dislocations is found
to be driven by the superposition of two independent contributions: (i) the
Peach-Koehler force derived from the change of a Lyapunov potential with
pattern wave number; (ii) a non-potential advection force on the dislocation
core by its self-generated mean flow. Their competition allows for the first
time to understand the experimentally observed bound dislocation pairs.
