An IC-MRCI ansatz was employed with hydrogen and helium [5s,4p,3d,2f] and beryllium [9s,8p,6d,4f,2g] single-particle basis sets to characterise the ground electronic states of BeH2, HBeHe⁺ and BeHe²₂⁺. CCSD(T) and IC-MRCI equilibrium structures for both these molecules are in excellent agreement with predicted trends in terms of geometry, vibrational frequencies and potential well depths. Discrete IC-MRCI potential energy surfaces consisting of 89 and 87 points were constructed for the HBeHe⁺ and BeHe²₂⁺ ground states, respectively. Padé approximants were employed to construct analytical representations of the surfaces of HBeHe⁺ and BeHe²₂⁺, yielding (χ2)1/2 values of 64.2 and 31.4 μEh, respectively.
Chemical Physics Letters Vol. 442, Issue 4-6, p. 194-200