The recently proposed (explicitly correlated) r 1 2 -MR-ACPF method is applied to the ground state (X 1 Σ g + ) potential of Be 2 . A large [19s11p6d4f3g2h] basis set and a valence-CAS reference space (60 CSFs) are used. At long range, the reference space is augmented by {3s,3p} orbitals (568 CSFs). The calculated dissociation energy (898+/-8 cm - 1 ) is considerably larger than the experimental estimate (790+/-30 cm - 1 ). The other molecular constants, however, are in good agreement. Our potential is close to the one calculated by Starck and Meyer [Chem. Phys. Lett. 258 (1996) 421].