  We have investigated the structure of double quantum dots vertically coupled
at zero magnetic field within local spin-density functional theory. The dots
are identical and have a finite width, and the whole system is axially
symmetric. We first discuss the effect of thickness on the addition spectrum of
one single dot. Next, we describe the structure of coupled dots as a function
of the interdot distance for different electron numbers. Addition spectra,
Hund's rule and molecular-type configurations are discussed. It is shown that
self-interaction corrections to the density functional results do not play a
very important role in the calculated addition spectra.
