Vertically coupled double quantum rings submitted to a perpendicular magnetic field B are addressed within
the local spin-density-functional theory. We describe the structure of quantum ring molecules containing up to
40 electrons considering different inter-ring distances and intensities of the applied magnetic field. When the
rings are quantum mechanically strongly coupled, only bonding states are occupied and the addition spectrum
of the artificial molecules resembles that of a single-quantum ring, with some small differences appearing as an
effect of the magnetic field. Despite the latter’s tendency to flatten the spectra, in the strong-coupling limit,
some clear peaks are still found even when B 0 that can be interpretated from the single-particle energy levels
similarly as in the zero magnetic field case, namely, in terms of closed-shell and Hund’s-rule configurations. By
increasing the inter-ring distance, the occupation of the first antibonding orbitals washes out such structures
and the addition spectra become flatter and irregular. In the weak-coupling regime, numerous isospin oscillations
are found as functions of
