MCSCF calculations of NMR spin--spin coupling constant of the HF molecule

The dependence of spin–spin NMR coupling constants on the basis set and electron correlation has been investigated for the hydrogen fluoride using Hartree–Fock (HF-SCF) and multiconfigurational self-consistent field (MCSCF) wave functions. The effect of the size, contraction, and tight s-type, augmented and polarization functions in the basis sets is analyzed. MCSCF wave functions with different number of active orbitals and excited electrons were used within the frozen-core approximation and with all-electron calculations. The correlation effect associated with the core electrons is not negligible. An approximation to determine spin–spin coupling constants at high level of electron correlation and reduced computational cost is applied satisfactorily. The best calculated and estimated 1JFH couplings are 544.20 and 536.63 Hz, respectively, with all electron correlation. Both values agree with the experimental one within the error bars (525±20 Hz). © 2000 American Institute of Physics.