  In this study, the performance of the doubles-corrected higher random-phase
approximation (HRPA(D)) has been investigated in calculations of NMR spin-spin
coupling constants (SSCCs) for 58 molecules with the experimental values used
as the reference values. HRPA(D) is an approximation to the second-order
polarization propagator approximation (SOPPA), and is therefore computationally
less expensive than SOPPA. HRPA(D) performs comparable and sometimes even
better than SOPPA, and therefore when calculating SSCCs it should be considered
as an alternative to SOPPA. Furthermore, it was investigated whether a CCSD(T)
or MP2 geometry optimization was optimal for a SOPPA and a HRPA(D) SSCCs
calculation for 8 smaller molecules. CCSD(T) is the optimal geometry
optimization for the SOPPA calculation, and MP2 was optimal for the HRPA(D)
SSCC calculations.
