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

## TL;DR

This paper introduces a new method to calculate nuclear spin-spin coupling density functions using atomic orbitals and includes all four Ramsey terms for better understanding of molecular interactions.

## Contribution

The novel contribution is a method for computing spin–spin coupling density functions that includes all four Ramsey terms at HF and DFT levels.

## Key findings

- The method enables visualization of spin polarization mechanisms.
- Through-space and through-bond interactions are clarified using all four Ramsey contributions.
- The approach is applied to several molecules for detailed analysis.

## Abstract

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 current density 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.