The potential curve, dissociation energy, equilibrium internuclear distance, and spectroscopic constants for the ground state of the Ca2 molecule are calculated with the help of the generalized relativistic effective core potential method, which allows one to exclude the inner core electrons from the calculations and to take the relativistic effects into account effectively. Extensive generalized correlation basis sets were constructed and used. The scalar relativistic coupled cluster method with corrections for high-order cluster amplitudes is used for the correlation treatment. The results are analyzed and compared with the experimental data and corresponding all-electron results. © 2013 Wiley Periodicals, Inc.