M. E. HARDING, J. VÁZQUEZ, J. F. STANTON, Institute for Theoretical Chemistry, Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, TX 78712 , USA.
For several potentials a detailed comparison of vibrational energy levels obtained via variational calculations employing the complete vibrational Hamiltonian and second-order vibrational perturbation theory (VPT2) is carried out.