AB-INITIO STUDY OF MOLECULAR G-TENSORS

The molecular g-tensors for the molecules NO2, CO2-, C3H5, H2CO+, and NF3+ are calculated at the unrestricted Hartree-Fock (UHF) level using the Rayleigh-Schrodinger perturbation approach. All one-electron term s have been evaluated, including the relativistic mass correction, the one-electron spin-Zeeman gauge correction, and a second-order term in volving the spin-orbit coupling and the orbital-Zeeman interaction. Th e relative importance of the first-order terms is found to be quite su bstantial. For first-row molecules, their total contribution is often of the same order of magnitude as of the second-order contribution, in some instances even larger. A study on the basis-set dependence of th ese g-tensors has been conducted. At this level, the most important ba sis-set criterion is shown to be a satisfactory description of the val ence regions. Finally, the gauge dependence of these g-tensor calculat ions has been systematically studied. This dependence seems to be subs tantially reduced for basis sets which include polarization functions. (C) 1995 John Wiley and Sons, Inc.