  The dissociation energy, equilibrium distance, and spectroscopic constants
for the $^1\Sigma_g^+$ ground state of the Yb$_2$ molecule are calculated. The
relativistic effects are introduced through generalized relativistic effective
core potentials with very high precision. The scalar relativistic coupled
cluster method particularly well suited for closed-shell van-der-Waals systems
is used for the correlation treatment. Extensive generalized correlation basis
sets were constructed and employed. The relatively small corrections for
high-order cluster amplitudes and spin-orbit interactions are taken into
account using smaller basis sets and the spin-orbit density functional theory.
