Full configuration interaction calculation of Be_3

摘要

The full configuration interaction (FCI) study of the ground state of the neutral beryllium trimer has been performed using an atomic natural orbitals [3s2p 1d] basis set.Both triangular and linear structures have been considered for the Be_3 cluster.The optimal geometry for the equilateral triangle has been calculated.The potential energy cut sections along the normal a'_1 mode and one of the components of the e' mode have then been studied.The FCI symmetric atomization potential of the linear cluster is also reported.It shows a secondary van der Waals minimum at a long bond distance.All singular points in the potential energy curves are characterized.Other properties,like dissociation energies D_e and vibrational frequencies,have been estimated from a fourth-order fitting of a large range of points around the minima.The calculated FCI wave number values for the v_1 and v_2 normal modes are (467.33+-0.43) cm~(-1) and (390.77+-0.56) cm~(-1).