Nuclear Spin–Spin Coupling Density Functions: Through-Bond and Through-Space Interactions

A new method based on the solution of time-independent standard response equation has been developed for the calculation of spin-spin coupling density functions, entirely in the atomic orbital basis at both HF and DFT (GGA and hybrid GGA) level of theory. The study is not limited to the Fermi contact alone, but also includes all four Ramsey terms, which have sometimes been shown to be non-negligible. The <i>current density</i> induced by nuclear magnetic dipoles represents the leading motif followed in the development of the theory. A few molecules have been analyzed in detail. The mechanism of spin polarization can be visualized, and the distinction between through-space and through-bond interactions can now be understood in terms of all four Ramsey contributions.