Nuclear Spin-Spin Coupling Constants from Auxiliary Density Functional Theory.

Area of Science:

• Quantum chemistry
• Computational physics
• Theoretical chemistry

Background:

• Indirect spin-spin coupling constants (NSSCCs) are crucial for interpreting NMR spectra.
• Accurate and efficient calculation of NSSCCs is computationally demanding.
• Auxiliary Density Functional Theory (ADFT) offers a promising framework for electronic structure calculations.

Purpose of the Study:

• To present working equations for calculating NSSCCs using ADFT.
• To introduce an implementation based on auxiliary density perturbation theory (ADPT).
• To demonstrate the computational efficiency and scalability of the new method.

Main Methods:

• Calculation of NSSCC contributions (Fermi-contact, spin-dipole, spin-orbit terms) as analytic second-order ADFT energy derivatives.
• Utilizing auxiliary density perturbation theory (ADPT) for perturbed density matrix elements.
• Employing analytic kernel implementations for Local Density Approximation (LDA) and Generalized Gradient Approximation (GGA) for improved performance.

Main Results:

• ADPT-calculated NSSCCs show comparable accuracy to Kohn-Sham DFT and favorable agreement with post-Hartree-Fock results.
• Validation against experimental data for small molecules confirms the reliability of the ADPT NSSCC implementation.
• Benchmark calculations on amylose chains demonstrate efficient parallel scaling.

Conclusions:

• The developed ADPT NSSCC method provides accurate results comparable to established methods.
• The implementation is computationally efficient and scales well for parallel architectures.
• This approach enables routine calculation of NSSCCs for large nanosystems exceeding 1000 atoms.