Ab initio calculations of the electronic structure of the ground states of HBeHe+ and

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 BeHe 2 2 + . 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 BeHe 2 2 + ground states, respectively. Padé approximants were employed to construct analytical representations of the surfaces of HBeHe+ and BeHe 2 2 + , yielding (χ2)1/2 values of 64.2 and 31.4 μEh, respectively.