High level ab initio calculations, up to (R)CCSD(T) as well as B3LYP have been performed on, radium diastatide, RaAt2, employing effective core potentials augmented with large, flexible valence basis sets. RaAt2 is found to have a bent equilibrium geometry, with a bond angle of similar to134.50, but a very low barrier to linearity. In addition, we performed calculations on the lowest cationic states, and calculate the first adiabatic ionization energy to be 7.41 eV, corresponding to a (XB2)-B-2 <-- X(1)A(1) process. We also calculate the energies of the lowest neutral states and find that RaAt2 is likely to absorb in the ultraviolet. (C) 2003 Elsevier Science B.V. All rights reserved.