Journal of Chemical Physics, Vol.119, No.9, 4694-4699, 2003
An ab initio, analytically fitted, global potential energy surface for the ground electronic state of He-3(+)
An analytical, global potential energy surface for the ground electronic potential energy surface (PES) for the He-3(+) ion has been constructed by fitting ab initio energy values calculated at the QCISD(T)/aug-cc-pVTZ level of theory for 935 geometric configurations to a many body expansion type functional form appended with ion-induced dipole terms to describe the long range interactions. The PES is adiabatically constrained to the ground electronic state by requiring the two atoms with the shortest separation in any particular geometry to be described by the embedded two-body He-2(+) potential. A transition state for the positional interchange of the middle and end atoms of the linear, centrosymmetric equilibrium geometry is identified and lies about 300 cm(-1) below the energy of the He-2(+)+He dissociation products. The nature of the PES near a seam of conical intersections between the ground and first excited electronic states occurring at D-3h geometries is discussed. (C) 2003 American Institute of Physics.