Calculation of Magnetic Shielding Constants of Diatomic Molecules. I. General Theory and Application to HF Molecule

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Abstract
A general method is derived for the calculation of magnetic shielding constants of diatomic molecules from SCF LCAO MO functions. The method is based on the introduction of gauge‐invariant atomic orbitals and is similar with previous calculations of diamagnetic susceptibilities. The only approximation that is used, in addition to the uncertainties in the wavefunctions, is connected with the determination of certain effective average excitation energies. The method is applied to the HF molecule and leads to a value of 4.009×10−5 for the proton shielding constant and of −7.058×10−5 for the second‐order paramagnetic term. The agreement with the corresponding experimental quantities, 3.13×10−5 and −7.96×10−5, respectively, is fair. A value of 40.589×10−5 is obtained for the fluorine shielding constant and of −7.570×10−5 for the second‐order paramagnetic term. The agreement with the experimental second‐order paramagnetic term, −6.79×10−5, is quite satisfactory.