Ab initio potential curves for the X2Σu+ and B2Σg+ states of Be2+: Existence of a double minimum

► Accurate ab initio calculations of the X2Σu+ and B2Σg+ ground states of the Be2+ dimer. ► The B2Σg+ ground state of Be2+ has a multi-reference character. ► The B2Σg+ state has a double minimum instead of a purely repulsive nature. ► Determination of spectroscopic constants for both ground states. ► Calculation of transition moments, polarizabilities and dispersion coefficients.