Ab initio properties and potential energy surface of the ground electronic state of

UCCSD(T) and IC-MRCI methods have been employed in conjunction with large contracted basis sets for He [5s, 4p, 3d, 2f] and Be [9s, 8p, 6d, 4f, 2g] to characterize the ground electronic state of BeHe 2 + . For both UCCSD(T) and IC-MRCI wave functions, basis set superposition errors were included, with size-extensivity corrections included for IC-MRCI calculations. UCCSD(T) and IC-MRCI results are in agreement with predicted trends in geometry, vibration frequencies and potential well-depths. A 45-point potential energy surface was calculated using IC-MRCI from which a (4,4) Padé analytical function was constructed yielding an absolute error to the fit of the surface (χ2)1/2 of 3.88 cm−1.