  One of the celebrated tools in explaining the Hydrogen atom is
Born-Oppenheimer approximation. The resemblance of $QQ\bar{q}\bar{q}$
tetraquarks to Hydrogen atom within Quantum chromodynamics (QCD) implies usage
of Born-Oppenheimer approximation for these multiquark states. In this work, we
use dynamical diquark model to calculate mass spectra and sizes of doubly
charmed and charged tetraquark states denoted as $T_{cc}^{++}$. Our results for
mass spectra indicate some bound state candidates with respect to corresponding
two-meson thresholds. Calculation of expectation values of $\sqrt{\langle r^2
\rangle}$ reflects that doubly charmed and charged tetraquark states are
compact.
