Near Hartree-Fock calculations on I₂ and its positive and negative ions

Potential curves from single configuration SCF calculations near the complete basis set limit are reported for ground state I2( 1Σ+), ground state I2-( 2Σ+), and the lowest I2+( 2Φ) and I2+(2Σ +) states. Orbitals are expanded in a Slater basis; the Hamiltonian is the usual nonrelativistic one with no spin-orbit and other relativistic effects. The calculations are done to provide a benchmark for model-potential, multiconfiguration, and relativistic and spin-orbit studies. The effect of performing calculations in a symmetry lower than that of the nuclear frame is discussed, and the unusual example of two stable SCF solutions at a given nuclear separation, both computed in the lower symmetry, is demonstrated for I2+(2Π). An experimental value for D e(I2-) of 1.07±0.1 eV is derived; compared with the Hartree-Fock computed value of 0.60J±0.05 eV. Potential curves are analysed for spectroscopic constants. The Hartree-Fock electron affinity of I2 is 2.17±0.1 eV compared with observed 2.58±0.1 eV. The Hartree-Fock quadrupole moment of the I2 molecule in its ground state is 6.24x10-26 esu cm2. © 1980 American Institute of Physics.